Initial Open Sourcing of React Native Compatibility Check (#49311)

Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/49311

This tool enables checking the boundary between JavaScript and Native for
backwards incompatible changes to protect against crashes.

This is useful for:

- Local Development
- Over the Air updates on platforms that support it
- Theoretically: Server Components with React Native

Check out the Readme for more information

Changelog: [General][Added] Open Sourcing React Native's Compatibility Check

Reviewed By: yungsters

Differential Revision: D69277991

fbshipit-source-id: 886a983d4b17609ce771cdd93b75f34bbd8417dc

packages/react-native-compatibility-check/.gitignore

@@ -0,0 +1 @@
+lib

packages/react-native-compatibility-check/CONTRIBUTING.md

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+This tool is essentially a type checker, and as such it can be difficult to
+understand the data flow. Luckily, there are fairly extensive tests which can
+aid in ramping up.
+
+This tool is made up of 3 primary stages: TypeDiffing, VersionDiffing, and
+ErrorFormatting.
+
+At a high level, the schemas are passed to TypeDiffing which is the pure
+typechecker. It returns all differences between the types. VersionDiffing then
+interprets these results and decides if some of those changes are actually safe
+in the context of React Native’s JS/Native boundary.
+
+For example, if you have a NativeModule method that returns a string union
+`small | medium | large`. Any changes to that union would be flagged by
+TypeDiffing as incompatible. However, adding a value to that union is safe
+because it ensures your JS code handles more cases than native returns. Removing
+a value from that union isn’t safe though because it means your JS no longer
+handles something native might return which could cause an exception.
+
+VersionDiffing encodes the logic of what is safe and what isn’t;
+property/union/enum additions and removals, changing something from optional to
+required and vice versa, etc. VersionDiffing has knowledge of components and
+modules.
+
+VersionDiffing returns a set of incompatible changes, which then gets passed to
+ErrorFormatting. ErrorFormatting does as you’d expect, converting these deep
+objects into nicely formatted strings.
+
+When contributing, some principles:
+
+- Keep TypeDiffing and ErrorFormatting pure. They should only know about
+  JavaScript types, not React Native specific concepts
+- Add tests for every case you can think of. This codebase can be complex and
+  hard to reason about when making changes. The only way to stay sane is to be
+  able to rely on the tests to catch anything bad you’ve done. Do yourself and
+  future contributors a favor.

packages/react-native-compatibility-check/README.md

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+# **React Native compatibility-check**
+
+Status: Experimental (stage 1)
+
+Work In Progress. Documentation is lacking, and intended to be used by power
+users at this point.
+
+This tool enables checking the boundary between JavaScript and Native for
+backwards incompatible changes to protect against crashes.
+
+This is useful for:
+
+- Local Development
+- Over the Air updates on platforms that support it
+- Theoretically: Server Components with React Native
+
+## **Motivating Problems**
+
+Let’s look at some motivating examples for this project.
+
+> [!NOTE] 
+> The examples below are written with Flow, but the compatibility-check
+> tool is agnostic to the types you write. The compatibility-check runs on JSON
+> schema files, most commonly generated by the
+> [@react-native/codegen](https://www.npmjs.com/package/@react-native/codegen)
+> tool which supports both TypeScript and Flow.
+
+### **Adding new methods**
+
+You might have an Analytics Native Module in your app, and you last built the
+native client a couple of days ago:
+
+```javascript
+export interface Spec extends TurboModule {
+  log: (eventName: string, content: string) => void;
+}
+```
+
+And you are working on a change to add a new method to this Native Module:
+
+```javascript
+export interface Spec extends TurboModule {
+  log: (eventName: string, content: string) => void;
+  logError: (message: string) => void;
+}
+```
+
+```
+NativeAnalytics.logError('Oh No! We hit a crash')
+```
+
+Since you are working on this, you’ve built a new native client and tested the
+change on your computer and everything works.
+
+However, when your colleague pulls your latest changes and tries to run it,
+they’ll get a crash `logError is not a function`. They need to rebuild their
+native client\!
+
+Using this tool, you can detect this incompatibility at build time, getting an
+error that looks like:
+
+```
+NativeAnalytics: Object added required properties, which native will not provide
+  -- logError
+```
+
+Errors like this can occur for much more nuanced reasons than adding a method.
+For example:
+
+### **Sending native new union values**
+
+```javascript
+export interface Spec extends TurboModule {
+  // You add 'system' to this union
+  +setColorScheme: (color: 'light' | 'dark') => void;
+}
+```
+
+If you add a new option of `system` and add native support for that option, when
+you call this method with `system` on your commit it would work but on an older
+build not expecting `system` it will crash. This tool will give you the error
+message:
+
+```
+ColorManager.setColorScheme parameter 0: Union added items, but native will not expect/support them
+  -- position 3 system
+```
+
+### **Changing an enum value sent from native**
+
+As another example, say you are getting the color scheme from the system as an
+integer value, used in JavaScript as an enum:
+
+```javascript
+enum TestEnum {
+  LIGHT = 1,
+  DARK = 2,
+  SYSTEM = 3,
+}
+
+export interface Spec extends TurboModule {
+  getColorScheme: () => TestEnum;
+}
+```
+
+And you realize you actually need native to send `-1` for System instead of 3\.
+
+```javascript
+enum TestEnum {
+  LIGHT = 1,
+  DARK = 2,
+  SYSTEM = -1,
+}
+```
+
+If you make this change and run the JavaScript on an old build, it might still
+send JavaScript the value 3, which your JavaScript isn’t handling anymore\!
+
+This tool gives an error:
+
+```javascript
+ColorManager: Object contained a property with a type mismatch
+   -- getColorScheme: has conflicting type changes
+       --new: ()=>Enum<number>
+       --old: ()=>Enum<number>
+       Function return types do not match
+           --new: ()=>Enum<number>
+           --old: ()=>Enum<number>
+           Enum types do not match
+               --new: Enum<number> {LIGHT = 1, DARK = 2, SYSTEM = -1}
+               --old: Enum<number> {LIGHT = 1, DARK = 2, SYSTEM = 3}
+               Enum contained a member with a type mismatch
+                   -- Member SYSTEM: has conflicting changes
+                       --new: -1
+                       --old: 3
+                       Numeric literals are not equal
+                           --new: -1
+                           --old: 3
+
+```
+
+## **Avoiding Breaking Changes**
+
+You can use this tool to either detect changes locally to warn that you need to
+install a new native build, or when doing OTA you might need to guarantee that
+the changes in your PR are compatible with the native client they’ll be running
+in.
+
+### **Example 1**
+
+In example 1, when adding logError, it needs to be optional to be safe:
+
+```javascript
+export interface Spec extends TurboModule {
+  log: (eventName: string, content: string) => void;
+  logError?: (message: string) => void;
+}
+```
+
+That will enforce if you are using TypeScript or Flow that you check if the
+native client supports logError before calling it:
+
+```javascript
+if (NativeAnalytics.logError) {
+  NativeAnalytics.logError('Oh No! We hit a crash');
+}
+```
+
+### **Example 2**
+
+When you want to add '`system'` as a value to the union, modifying the existing
+union is not safe. You would need to add a new optional method that has that
+change. You can clean up the old method when you know that all of the builds you
+ever want to run this JavaScript on have native support.
+
+```javascript
+export interface Spec extends TurboModule {
+  +setColorScheme: (color: 'light' | 'dark') => void
+  +setColorSchemeWithSystem?: (color: 'light' | 'dark' | 'system') => void
+}
+```
+
+### **Example 3**
+
+Changing a union case is similar to Example 2, you would either need a new
+method, or support the existing value and the new `-1`.
+
+```
+enum TestEnum {
+  LIGHT = 1,
+  DARK = 2,
+  SYSTEM = 3,
+  SYSTEM_ALSO = -1,
+}
+```
+
+## **Installation**
+
+```
+yarn add @react-native/compatibility-check
+```
+
+## **Usage**
+
+To use this package, you’ll need a script that works something like this:
+
+This script checks the compatibility of a React Native app's schema between two
+versions. It takes into account the changes made to the schema and determines
+whether they are compatible or not.
+
+```javascript
+import {compareSchemas} from '@react-native/compatibility-check';
+const util = require('util');
+
+async function run(argv: Argv, STDERR: string) {
+  const debug = (log: mixed) => {
+    argv.debug &&
+      console.info(util.inspect(log, {showHidden: false, depth: null}));
+  };
+
+  const currentSchema =
+    JSON.parse(/*you'll read the file generated by codegen wherever it is in your app*/);
+  const previousSchema =
+    JSON.parse(/*you'll read the schema file that you persisted from when your native app was built*/);
+
+  const safetyResult = compareSchemas(currentSchema, previousSchema);
+
+  const summary = safetyResult.getSummary();
+  switch (summary.status) {
+    case 'ok':
+      debug('No changes in boundary');
+      console.log(JSON.stringify(summary));
+      break;
+    case 'patchable':
+      debug('Changes in boundary, but are compatible');
+      debug(result.getDebugInfo());
+      console.log(JSON.stringify(summary));
+      break;
+    default:
+      debug(result.getDebugInfo());
+      console.error(JSON.stringify(result.getErrors()));
+      throw new Error(`Incompatible changes in boundary`);
+  }
+}
+```

packages/react-native-compatibility-check/package.json

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+{
+  "name": "@react-native/compatibility-check",
+  "version": "0.0.1",
+  "description": "Check a React Native app's boundary between JS and Native for incompatibilities",
+  "license": "MIT",
+  "repository": {
+    "type": "git",
+    "url": "git+https://github.com/facebook/react-native.git",
+    "directory": "packages/react-native-compatibility-check"
+  },
+  "homepage": "https://github.com/facebook/react-native/tree/HEAD/packages/react-native-compatibility-check#readme",
+  "keywords": [
+    "boundary",
+    "crashes",
+    "native",
+    "codegen",
+    "tools",
+    "react-native"
+  ],
+  "bugs": "https://github.com/facebook/react-native/issues",
+  "engines": {
+    "node": ">=18"
+  },
+  "exports": {
+    ".": "./src/index.js",
+    "./package.json": "./package.json"
+  },
+  "files": [
+    "dist"
+  ],
+  "dependencies": {
+    "@react-native/codegen": "0.79.0-main"
+  },
+  "devDependencies": {
+    "flow-remove-types": "^2.237.2",
+    "rimraf": "^3.0.2"
+  }
+}

packages/react-native-compatibility-check/src/ComparisonResult.js

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+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict
+ * @format
+ */
+
+import type {
+  CompleteTypeAnnotation,
+  NamedShape,
+  NativeModuleEnumMember,
+} from '@react-native/codegen/src/CodegenSchema';
+
+type TypeAnnotationComparisonError = {
+  type: 'TypeAnnotationComparisonError',
+  message: string,
+  newerAnnotation: CompleteTypeAnnotation,
+  olderAnnotation: CompleteTypeAnnotation,
+  previousError?: TypeComparisonError,
+};
+type TypeInformationComparisonError = {
+  type: 'TypeInformationComparisonError',
+  message: string,
+  newerType: CompleteTypeAnnotation,
+  olderType: CompleteTypeAnnotation,
+  previousError?: TypeComparisonError,
+};
+type PropertyComparisonError = {
+  type: 'PropertyComparisonError',
+  message: string,
+  mismatchedProperties: Array<{
+    property: string,
+    fault?: TypeComparisonError,
+    ...
+  }>,
+  previousError?: TypeComparisonError,
+};
+type PositionalComparisonError = {
+  type: 'PositionalComparisonError',
+  message: string,
+  erroneousItems: Array<[number, CompleteTypeAnnotation]>,
+  previousError?: TypeComparisonError,
+};
+type MemberComparisonError = {
+  type: 'MemberComparisonError',
+  message: string,
+  mismatchedMembers: Array<{
+    member: string,
+    fault?: TypeComparisonError,
+  }>,
+  previousError?: TypeComparisonError,
+};
+export type TypeComparisonError =
+  | TypeAnnotationComparisonError
+  | TypeInformationComparisonError
+  | PropertyComparisonError
+  | PositionalComparisonError
+  | MemberComparisonError;
+
+// Collects changes that may be type safe within parameters, unions, intersections, and tuples
+export type PositionalComparisonResult = {
+  typeKind: 'stringUnion' | 'union' | 'intersection' | 'parameter' | 'tuple',
+  // Nested changes stores the position of the old type followed by new
+  // Except for union and intersection, new position === old position
+  nestedChanges: Array<[number, number, ComparisonResult]>,
+  // These properties should never occur for a tuple
+  addedElements?: Array<[number, CompleteTypeAnnotation]>,
+  removedElements?: Array<[number, CompleteTypeAnnotation]>,
+  ...
+};
+export type FunctionComparisonResult = {
+  returnType?: ComparisonResult,
+  // The following should always have typeKind 'parameter'
+  parameterTypes?: PositionalComparisonResult,
+  ...
+};
+
+// Array<NamedShape<Nullable<NativeModuleBaseTypeAnnotation>>>
+
+export type PropertiesComparisonResult = {
+  addedProperties?: $ReadOnlyArray<NamedShape<CompleteTypeAnnotation>>,
+  missingProperties?: $ReadOnlyArray<NamedShape<CompleteTypeAnnotation>>,
+  errorProperties?: Array<{
+    property: string,
+    fault?: TypeComparisonError,
+    ...
+  }>,
+  madeStrict?: Array<{
+    property: string,
+    furtherChanges?: ComparisonResult,
+    ...
+  }>,
+  madeOptional?: Array<{
+    property: string,
+    furtherChanges?: ComparisonResult,
+    ...
+  }>,
+  nestedPropertyChanges?: Array<[string, ComparisonResult]>,
+  ...
+};
+export type MembersComparisonResult = {
+  addedMembers?: Array<NativeModuleEnumMember>,
+  missingMembers?: Array<NativeModuleEnumMember>,
+  errorMembers?: Array<{
+    member: string,
+    fault?: TypeComparisonError,
+  }>,
+};
+export type NullableComparisonResult = {
+  /* Four possible cases of change:
+     void goes to T?   :: typeRefined !optionsReduced
+     T?   goes to void :: typeRefined optionsReduced
+     T    goes to T?   :: !typeRefined !optionsReduced
+     T?   goes to T    :: !typeRefined optionsReduced
+  */
+  typeRefined: boolean,
+  optionsReduced: boolean,
+  // interiorLog not available if either type is void
+  interiorLog: ?ComparisonResult,
+  newType: ?CompleteTypeAnnotation,
+  oldType: ?CompleteTypeAnnotation,
+  ...
+};
+export type ComparisonResult =
+  | {status: 'matching'}
+  | {status: 'skipped'}
+  | {status: 'nullableChange', nullableLog: NullableComparisonResult}
+  | {status: 'properties', propertyLog: PropertiesComparisonResult}
+  | {status: 'members', memberLog: MembersComparisonResult}
+  | {status: 'functionChange', functionChangeLog: FunctionComparisonResult}
+  | {status: 'positionalTypeChange', changeLog: PositionalComparisonResult}
+  | {status: 'error', errorLog: TypeComparisonError};
+
+export function isPropertyLogEmpty(
+  result: PropertiesComparisonResult,
+): boolean {
+  return !(
+    result.addedProperties ||
+    result.missingProperties ||
+    result.nestedPropertyChanges ||
+    result.madeStrict ||
+    result.madeOptional ||
+    result.errorProperties
+  );
+}
+
+export function isMemberLogEmpty(result: MembersComparisonResult): boolean {
+  return !(result.addedMembers || result.missingMembers || result.errorMembers);
+}
+
+export function isFunctionLogEmpty(result: FunctionComparisonResult): boolean {
+  return !(result.returnType || result.parameterTypes);
+}
+
+export function makeError(error: TypeComparisonError): ComparisonResult {
+  return {
+    status: 'error',
+    errorLog: error,
+  };
+}
+
+export function typeInformationComparisonError(
+  message: string,
+  newerType: CompleteTypeAnnotation,
+  olderType: CompleteTypeAnnotation,
+  previousError?: TypeComparisonError,
+): TypeComparisonError {
+  return {
+    type: 'TypeInformationComparisonError',
+    message,
+    newerType,
+    olderType,
+    previousError,
+  };
+}
+
+export function typeAnnotationComparisonError(
+  message: string,
+  newerAnnotation: CompleteTypeAnnotation,
+  olderAnnotation: CompleteTypeAnnotation,
+  previousError?: TypeComparisonError,
+): TypeComparisonError {
+  return {
+    type: 'TypeAnnotationComparisonError',
+    message,
+    newerAnnotation,
+    olderAnnotation,
+    previousError,
+  };
+}
+
+export function propertyComparisonError(
+  message: string,
+  mismatchedProperties: Array<{
+    property: string,
+    fault?: TypeComparisonError,
+    ...
+  }>,
+  previousError?: TypeComparisonError,
+): TypeComparisonError {
+  return {
+    type: 'PropertyComparisonError',
+    message,
+    mismatchedProperties,
+    previousError,
+  };
+}
+
+export function memberComparisonError(
+  message: string,
+  mismatchedMembers: Array<{
+    member: string,
+    fault?: TypeComparisonError,
+  }>,
+  previousError?: TypeComparisonError,
+): TypeComparisonError {
+  return {
+    type: 'MemberComparisonError',
+    message,
+    mismatchedMembers,
+    previousError,
+  };
+}
+
+export function positionalComparisonError(
+  message: string,
+  erroneousItems: Array<[number, CompleteTypeAnnotation]>,
+  previousError?: TypeComparisonError,
+): TypeComparisonError {
+  return {
+    type: 'PositionalComparisonError',
+    message,
+    erroneousItems,
+    previousError,
+  };
+}

packages/react-native-compatibility-check/src/DiffResults.js

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+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {
+  PropertiesComparisonResult,
+  TypeComparisonError,
+} from './ComparisonResult';
+import type {CompleteTypeAnnotation} from '@react-native/codegen/src/CodegenSchema';
+
+export type ErrorCode =
+  | 'addedProps'
+  | 'removedProps'
+  | 'changedParams'
+  | 'incompatibleTypes'
+  | 'requiredProps'
+  | 'optionalProps'
+  | 'nonNullableOfNull'
+  | 'nullableOfNonNull'
+  | 'removedUnionCases'
+  | 'addedUnionCases'
+  | 'addedEnumCases'
+  | 'removedEnumCases'
+  | 'removedIntersectCases'
+  | 'addedIntersectCases'
+  | 'removedModule'
+  | 'removedComponent';
+
+export type TypeStore = {
+  typeName: string,
+  typeInformation: CompleteTypeAnnotation,
+  ...
+};
+// Stores object properties that are added or removed which could be patchable
+export type ObjectTypeChangeStore = {
+  typeName: string,
+  newType: CompleteTypeAnnotation,
+  oldType: CompleteTypeAnnotation,
+  propertyChange: PropertiesComparisonResult,
+};
+export type ErrorStore = {
+  typeName: string,
+  errorCode: ErrorCode,
+  errorInformation: TypeComparisonError,
+};
+export type FormattedErrorStore = {
+  message: string,
+  errorCode: ErrorCode,
+};
+export type NativeSpecErrorStore = {
+  nativeSpecName: string,
+  omitted: boolean,
+  errorCode: ErrorCode,
+  errorInformation?: TypeComparisonError,
+  changeInformation?: DiffSet,
+};
+export type ExportableNativeSpecErrorStore = {
+  nativeSpecName: string,
+  omitted: boolean,
+  errorCode: ErrorCode,
+  errorInformation?: TypeComparisonError,
+  changeInformation?: ExportableDiffSet,
+};
+export type DiffSet = {
+  newTypes: Set<TypeStore>,
+  deprecatedTypes: Set<TypeStore>,
+  objectTypeChanges: Set<ObjectTypeChangeStore>,
+  incompatibleChanges: Set<ErrorStore>,
+};
+type ExportableDiffSet = {
+  newTypes: Array<TypeStore>,
+  deprecatedTypes: Array<TypeStore>,
+  objectTypeChanges: Array<ObjectTypeChangeStore>,
+  incompatibleChanges: Array<ErrorStore>,
+};
+
+export type Framework = 'ReactNative';
+export type SchemaDiffers = {
+  incompatibleSpecs: ?Set<NativeSpecErrorStore>,
+};
+type ExportableSchemaDiffers = {
+  incompatibleSpecs: ?Array<ExportableNativeSpecErrorStore>,
+};
+export type SchemaDiffCategory = 'new' | 'deprecated' | SchemaDiffers;
+type ExportableSchemaDiffCategory =
+  | 'new'
+  | 'deprecated'
+  | ExportableSchemaDiffers;
+export type SchemaDiff = {
+  name: string,
+  framework: Framework,
+  status: SchemaDiffCategory,
+};
+export type ExportableSchemaDiff = {
+  name: string,
+  framework: Framework,
+  status: ExportableSchemaDiffCategory,
+};
+
+export type Version = {
+  device: 'android' | 'ios',
+  number: string,
+  ...
+};
+
+export type Incompatible = {
+  framework: Framework,
+  incompatibleSpecs?: Array<NativeSpecErrorStore>,
+};
+export type IncompatiblityReport = {
+  [hasteModuleName: string]: Incompatible,
+};
+export type DiffSummary = {
+  /** status records how the diff compares against older versions
+   * ok: there are no changes that impact older versions
+   * patchable: there are additions (or modifications) that are not suported
+   *            in older versions but is safe with an auto-generated patch
+   * incompatible: there are modifications that are not safe for use with older
+   *            versions and are not fixable with an auto-generated patchable
+   */
+  status: 'ok' | 'patchable' | 'incompatible',
+  // If there are incompatible changes, provide a record of them, otherwise {}
+  incompatibilityReport: IncompatiblityReport,
+};
+
+export type FormattedIncompatible = {
+  framework: Framework,
+  incompatibleSpecs?: Array<FormattedErrorStore>,
+};
+
+export type FormattedIncompatiblityReport = {
+  [hasteModuleName: string]: FormattedIncompatible,
+};
+
+export type FormattedDiffSummary = {
+  /** status records how the diff compares against older versions
+   * ok: there are no changes that impact older versions
+   * patchable: there are additions (or modifications) that are not suported
+   *            in older versions but is safe with an auto-generated patch
+   * incompatible: there are modifications that are not safe for use with older
+   *            versions and are not fixable with an auto-generated patchable
+   */
+  status: 'ok' | 'patchable' | 'incompatible',
+  // If there are incompatible changes, provide a record of them, otherwise {}
+  incompatibilityReport: FormattedIncompatiblityReport,
+};
+
+function diffSetExporter(diffSet: DiffSet): ExportableDiffSet {
+  return {
+    newTypes: Array.from(diffSet.newTypes),
+    deprecatedTypes: Array.from(diffSet.deprecatedTypes),
+    objectTypeChanges: Array.from(diffSet.objectTypeChanges),
+    incompatibleChanges: Array.from(diffSet.incompatibleChanges),
+  };
+}
+
+export function nativeSpecErrorExporter(
+  nativeSpecError: NativeSpecErrorStore,
+): ExportableNativeSpecErrorStore {
+  if (nativeSpecError.changeInformation) {
+    return {
+      nativeSpecName: nativeSpecError.nativeSpecName,
+      omitted: nativeSpecError.omitted,
+      errorCode: nativeSpecError.errorCode,
+      errorInformation: nativeSpecError.errorInformation,
+      changeInformation: diffSetExporter(nativeSpecError.changeInformation),
+    };
+  }
+  return {
+    nativeSpecName: nativeSpecError.nativeSpecName,
+    omitted: nativeSpecError.omitted,
+    errorCode: nativeSpecError.errorCode,
+    errorInformation: nativeSpecError.errorInformation,
+  };
+}
+
+function schemaDiffCategoryExporter(
+  status: SchemaDiffCategory,
+): ExportableSchemaDiffCategory {
+  switch (status) {
+    case 'new':
+    case 'deprecated':
+      return status;
+    default:
+      return {
+        incompatibleSpecs: status.incompatibleSpecs
+          ? Array.from(status.incompatibleSpecs).map(nativeSpecErrorExporter)
+          : undefined,
+      };
+  }
+}
+
+export function schemaDiffExporter(
+  schemaDiff: SchemaDiff,
+): ExportableSchemaDiff {
+  return {
+    name: schemaDiff.name,
+    framework: schemaDiff.framework,
+    status: schemaDiffCategoryExporter(schemaDiff.status),
+  };
+}

packages/react-native-compatibility-check/src/ErrorFormatting.js

@@ -0,0 +1,309 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {TypeComparisonError} from './ComparisonResult';
+import type {
+  DiffSummary,
+  ErrorStore,
+  FormattedDiffSummary,
+  FormattedErrorStore,
+  FormattedIncompatible,
+  FormattedIncompatiblityReport,
+  NativeSpecErrorStore,
+} from './DiffResults';
+import type {CompleteTypeAnnotation} from '@react-native/codegen/src/CodegenSchema';
+
+function indentedLineStart(indent: number): string {
+  return '\n' + '  '.repeat(indent);
+}
+
+export function formatErrorMessage(
+  error: TypeComparisonError,
+  indent: number = 0,
+): string {
+  switch (error.type) {
+    case 'PropertyComparisonError':
+      const formattedProperties = error.mismatchedProperties.map(
+        individualPropertyError =>
+          indentedLineStart(indent + 1) +
+          '-- ' +
+          individualPropertyError.property +
+          (individualPropertyError.fault
+            ? ': ' +
+              formatErrorMessage(individualPropertyError.fault, indent + 2)
+            : ''),
+      );
+      return error.message + formattedProperties.join('');
+    case 'PositionalComparisonError':
+      const formattedPositionalChanges = error.erroneousItems.map(
+        ([index, type]) =>
+          indentedLineStart(indent + 1) +
+          '-- position ' +
+          index +
+          ' ' +
+          formatTypeAnnotation(type),
+      );
+      return error.message + formattedPositionalChanges.join('');
+    case 'TypeAnnotationComparisonError':
+      const previousError = error.previousError;
+
+      return (
+        error.message +
+        indentedLineStart(indent + 1) +
+        '--new: ' +
+        formatTypeAnnotation(error.newerAnnotation) +
+        indentedLineStart(indent + 1) +
+        '--old: ' +
+        formatTypeAnnotation(error.olderAnnotation) +
+        (previousError != null
+          ? indentedLineStart(indent + 1) +
+            '' +
+            formatErrorMessage(previousError, indent + 2)
+          : '')
+      );
+    case 'TypeInformationComparisonError':
+      // I'm not sure that this error type is possible with the codegen
+
+      return (
+        error.message +
+        indentedLineStart(indent + 1) +
+        '-- new: ' +
+        formatTypeAnnotation(error.newerType) +
+        indentedLineStart(indent + 1) +
+        '-- old: ' +
+        formatTypeAnnotation(error.olderType)
+      );
+    case 'MemberComparisonError':
+      const formattedMembers = error.mismatchedMembers.map(
+        individualMemberError =>
+          indentedLineStart(indent + 1) +
+          '-- Member ' +
+          individualMemberError.member +
+          (individualMemberError.fault
+            ? ': ' + formatErrorMessage(individualMemberError.fault, indent + 2)
+            : ''),
+      );
+      return error.message + formattedMembers.join('');
+    default:
+      (error.type: empty);
+      return '';
+  }
+}
+
+function formatTypeAnnotation(annotation: CompleteTypeAnnotation): string {
+  switch (annotation.type) {
+    case 'AnyTypeAnnotation':
+      return 'any';
+    case 'ArrayTypeAnnotation':
+      return 'Array<' + formatTypeAnnotation(annotation.elementType) + '>';
+    case 'BooleanTypeAnnotation':
+      return 'boolean';
+    case 'EnumDeclaration': {
+      let shortHandType = '';
+      switch (annotation.memberType) {
+        case 'StringTypeAnnotation':
+          shortHandType = 'string';
+          break;
+        case 'NumberTypeAnnotation':
+          shortHandType = 'number';
+          break;
+        default:
+          (annotation.memberType: empty);
+          throw new Error('Unexpected enum memberType');
+      }
+
+      return `Enum<${shortHandType}>` + '';
+    }
+    case 'EnumDeclarationWithMembers': {
+      let shortHandType = '';
+      switch (annotation.memberType) {
+        case 'StringTypeAnnotation':
+          shortHandType = 'string';
+          break;
+        case 'NumberTypeAnnotation':
+          shortHandType = 'number';
+          break;
+        default:
+          (annotation.memberType: empty);
+          throw new Error('Unexptected enum memberType');
+      }
+
+      return (
+        `Enum<${shortHandType}> {` +
+        annotation.members
+          .map(
+            member => `${member.name} = ${formatTypeAnnotation(member.value)}`,
+          )
+          .join(', ') +
+        '}'
+      );
+    }
+    case 'FunctionTypeAnnotation':
+      return (
+        '(' +
+        annotation.params
+          .map(
+            param =>
+              param.name +
+              (param.optional ? '?' : '') +
+              ': ' +
+              formatTypeAnnotation(param.typeAnnotation),
+          )
+          .join(', ') +
+        ')' +
+        '=>' +
+        formatTypeAnnotation(annotation.returnTypeAnnotation)
+      );
+    case 'NullableTypeAnnotation':
+      return '?' + formatTypeAnnotation(annotation.typeAnnotation);
+    case 'NumberTypeAnnotation':
+      return 'number';
+    case 'DoubleTypeAnnotation':
+      return 'double';
+    case 'FloatTypeAnnotation':
+      return 'float';
+    case 'Int32TypeAnnotation':
+      return 'int';
+    case 'NumberLiteralTypeAnnotation':
+      return annotation.value.toString();
+    case 'ObjectTypeAnnotation':
+      return (
+        '{' +
+        annotation.properties
+          .map(
+            property =>
+              property.name +
+              (property.optional ? '?' : '') +
+              ': ' +
+              formatTypeAnnotation(property.typeAnnotation),
+          )
+          .join(', ') +
+        '}'
+      );
+    case 'StringLiteralTypeAnnotation':
+      // If the string is a number, disambiguate from a number literal by adding quotes
+      // Other things are obviously strings so quotes unconditionally would just add noise
+      return parseInt(annotation.value, 10).toString() === annotation.value ||
+        annotation.value.includes(' ')
+        ? `'${annotation.value}'`
+        : annotation.value;
+    case 'StringLiteralUnionTypeAnnotation':
+      return (
+        '(' +
+        annotation.types
+          .map(stringLit => formatTypeAnnotation(stringLit))
+          .join(' | ') +
+        ')'
+      );
+    case 'StringTypeAnnotation':
+      return 'string';
+    case 'UnionTypeAnnotation': {
+      const shortHandType =
+        annotation.memberType === 'StringTypeAnnotation'
+          ? 'string'
+          : annotation.memberType === 'ObjectTypeAnnotation'
+            ? 'Object'
+            : 'number';
+      return `Union<${shortHandType}>`;
+    }
+    case 'PromiseTypeAnnotation':
+      return 'Promise<' + formatTypeAnnotation(annotation.elementType) + '>';
+    case 'EventEmitterTypeAnnotation':
+      return (
+        'EventEmitter<' + formatTypeAnnotation(annotation.typeAnnotation) + '>'
+      );
+    case 'TypeAliasTypeAnnotation':
+    case 'ReservedTypeAnnotation':
+      return annotation.name;
+    case 'VoidTypeAnnotation':
+      return 'void';
+    case 'MixedTypeAnnotation':
+      return 'mixed';
+    case 'GenericObjectTypeAnnotation':
+      if (annotation.dictionaryValueType) {
+        return `{[string]: ${formatTypeAnnotation(annotation.dictionaryValueType)}`;
+      }
+
+      return 'Object';
+    default:
+      (annotation.type: empty);
+      return JSON.stringify(annotation);
+  }
+}
+
+export function formatErrorStore(errorStore: ErrorStore): FormattedErrorStore {
+  return {
+    message:
+      errorStore.typeName +
+      ': ' +
+      formatErrorMessage(errorStore.errorInformation),
+    errorCode: errorStore.errorCode,
+  };
+}
+
+export function formatNativeSpecErrorStore(
+  specError: NativeSpecErrorStore,
+): Array<FormattedErrorStore> {
+  if (specError.errorInformation) {
+    return [
+      {
+        message:
+          specError.nativeSpecName +
+          ': ' +
+          formatErrorMessage(specError.errorInformation),
+        errorCode: specError.errorCode,
+      },
+    ];
+  }
+
+  if (specError.changeInformation?.incompatibleChanges != null) {
+    return Array.from(specError.changeInformation.incompatibleChanges).map(
+      errorStore => formatErrorStore(errorStore),
+    );
+  }
+  // changeInformation does not contain incompatible changes
+  return [];
+}
+
+export function formatDiffSet(summary: DiffSummary): FormattedDiffSummary {
+  const summaryStatus = summary.status;
+  if (summaryStatus === 'ok' || summaryStatus === 'patchable') {
+    // $FlowFixMe I don't think we can ever get in this branch
+    return summary;
+  }
+  const hasteModules = Object.keys(summary.incompatibilityReport);
+  const incompatibles = summary.incompatibilityReport;
+  const formattedIncompatibilities: FormattedIncompatiblityReport = {};
+  hasteModules.forEach(hasteModule => {
+    const incompat = incompatibles[hasteModule];
+    const formattedIncompat: FormattedIncompatible = {
+      framework: incompat.framework,
+    };
+    if (incompat.incompatibleSpecs) {
+      // nested errors
+      formattedIncompat.incompatibleSpecs = incompat.incompatibleSpecs.reduce(
+        (
+          formattedModuleErrors: $ReadOnlyArray<FormattedErrorStore>,
+          specErrorStore,
+        ) =>
+          formattedModuleErrors.concat(
+            formatNativeSpecErrorStore(specErrorStore),
+          ),
+        [],
+      );
+    }
+
+    formattedIncompatibilities[hasteModule] = formattedIncompat;
+  });
+  return {
+    status: (summaryStatus: 'incompatible'),
+    incompatibilityReport: formattedIncompatibilities,
+  };
+}

packages/react-native-compatibility-check/src/SortTypeAnnotations.js

@@ -0,0 +1,290 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict
+ * @format
+ */
+
+import type {CompleteTypeAnnotation} from '@react-native/codegen/src/CodegenSchema';
+
+import invariant from 'invariant';
+
+export function sortTypeAnnotations(
+  annotations: $ReadOnlyArray<CompleteTypeAnnotation>,
+): Array<[number, CompleteTypeAnnotation]> {
+  const sortableArray = annotations.map(
+    (a, i): [number, CompleteTypeAnnotation] => [i, a],
+  );
+  return sortableArray.sort(compareTypeAnnotationForSorting);
+}
+
+const EQUALITY_MSG = 'typeA and typeB differ despite check';
+export function compareTypeAnnotationForSorting(
+  [originalPositionA, typeA]: [number, CompleteTypeAnnotation],
+  [originalPositionB, typeB]: [number, CompleteTypeAnnotation],
+): number {
+  if (typeA.type !== typeB.type) {
+    if (typeA.type === 'NullableTypeAnnotation') {
+      return compareTypeAnnotationForSorting(
+        [originalPositionA, typeA.typeAnnotation],
+        [originalPositionB, typeB],
+      );
+    }
+    if (typeB.type === 'NullableTypeAnnotation') {
+      return compareTypeAnnotationForSorting(
+        [originalPositionA, typeA],
+        [originalPositionB, typeB.typeAnnotation],
+      );
+    }
+    return (
+      typeAnnotationArbitraryOrder(typeA) - typeAnnotationArbitraryOrder(typeB)
+    );
+  }
+  switch (typeA.type) {
+    case 'AnyTypeAnnotation':
+      return 0;
+    case 'ArrayTypeAnnotation':
+      invariant(typeB.type === 'ArrayTypeAnnotation', EQUALITY_MSG);
+      return compareTypeAnnotationForSorting(
+        [originalPositionA, typeA.elementType],
+        [originalPositionB, typeB.elementType],
+      );
+    case 'BooleanTypeAnnotation':
+      return originalPositionA - originalPositionB;
+    case 'EnumDeclaration':
+      invariant(typeB.type === 'EnumDeclaration', EQUALITY_MSG);
+      return typeA.memberType.localeCompare(typeB.memberType);
+    case 'EnumDeclarationWithMembers':
+      invariant(typeB.type === 'EnumDeclarationWithMembers', EQUALITY_MSG);
+      return compareNameAnnotationArraysForSorting(
+        [originalPositionA, typeA.members.map(m => [m.name, m.value])],
+        [originalPositionB, typeB.members.map(m => [m.name, m.value])],
+      );
+    case 'FunctionTypeAnnotation':
+      invariant(typeB.type === 'FunctionTypeAnnotation', EQUALITY_MSG);
+      const parmComparison = compareAnnotationArraysForSorting(
+        [originalPositionA, typeA.params.map(p => p.typeAnnotation)],
+        [originalPositionB, typeB.params.map(p => p.typeAnnotation)],
+      );
+      if (parmComparison === 0) {
+        return compareTypeAnnotationForSorting(
+          [originalPositionA, typeA.returnTypeAnnotation],
+          [originalPositionB, typeB.returnTypeAnnotation],
+        );
+      }
+      return parmComparison;
+    case 'EventEmitterTypeAnnotation':
+      invariant(typeB.type === 'EventEmitterTypeAnnotation', EQUALITY_MSG);
+
+      return compareTypeAnnotationForSorting(
+        [originalPositionA, typeA.typeAnnotation],
+        [originalPositionB, typeB.typeAnnotation],
+      );
+    case 'GenericObjectTypeAnnotation':
+      invariant(typeB.type === 'GenericObjectTypeAnnotation', EQUALITY_MSG);
+
+      if (
+        typeA.dictionaryValueType == null &&
+        typeB.dictionaryValueType == null
+      ) {
+        return 0;
+      } else if (
+        typeA.dictionaryValueType != null &&
+        typeB.dictionaryValueType != null
+      ) {
+        return compareTypeAnnotationForSorting(
+          [originalPositionA, typeA.dictionaryValueType],
+          [originalPositionB, typeB.dictionaryValueType],
+        );
+      } else {
+        return typeA.dictionaryValueType == null ? -1 : 1;
+      }
+    case 'NullableTypeAnnotation':
+      invariant(typeB.type === 'NullableTypeAnnotation', EQUALITY_MSG);
+      return compareTypeAnnotationForSorting(
+        [originalPositionA, typeA.typeAnnotation],
+        [originalPositionB, typeB.typeAnnotation],
+      );
+    case 'NumberTypeAnnotation':
+    case 'Int32TypeAnnotation':
+    case 'FloatTypeAnnotation':
+    case 'DoubleTypeAnnotation':
+      return 0;
+    case 'NumberLiteralTypeAnnotation':
+      invariant(typeB.type === 'NumberLiteralTypeAnnotation', EQUALITY_MSG);
+      return typeA.value - typeB.value;
+    case 'ObjectTypeAnnotation':
+      invariant(typeB.type === 'ObjectTypeAnnotation', EQUALITY_MSG);
+      return compareNameAnnotationArraysForSorting(
+        [
+          originalPositionA,
+          typeA.properties.map(p => [p.name, p.typeAnnotation]),
+        ],
+        [
+          originalPositionB,
+          typeB.properties.map(p => [p.name, p.typeAnnotation]),
+        ],
+      );
+    case 'StringTypeAnnotation':
+      return originalPositionA - originalPositionB;
+    case 'StringLiteralTypeAnnotation':
+      invariant(typeB.type === 'StringLiteralTypeAnnotation', EQUALITY_MSG);
+      return typeA.value.localeCompare(typeB.value);
+    case 'StringLiteralUnionTypeAnnotation':
+      invariant(
+        typeB.type === 'StringLiteralUnionTypeAnnotation',
+        EQUALITY_MSG,
+      );
+      return compareAnnotationArraysForSorting(
+        [originalPositionA, typeA.types],
+        [originalPositionB, typeB.types],
+      );
+    case 'UnionTypeAnnotation':
+      invariant(typeB.type === 'UnionTypeAnnotation', EQUALITY_MSG);
+      return 0;
+    case 'VoidTypeAnnotation':
+      return 0;
+    case 'ReservedTypeAnnotation':
+      return 0;
+    case 'PromiseTypeAnnotation':
+      invariant(typeB.type === 'PromiseTypeAnnotation', EQUALITY_MSG);
+      return compareTypeAnnotationForSorting(
+        [originalPositionA, typeA.elementType],
+        [originalPositionB, typeB.elementType],
+      );
+    case 'TypeAliasTypeAnnotation':
+      return 0;
+    case 'MixedTypeAnnotation':
+      return 0;
+    default:
+      (typeA.type: empty);
+      return -1;
+  }
+}
+
+function nameComparison(
+  [nameA]: [string, CompleteTypeAnnotation],
+  [nameB]: [string, CompleteTypeAnnotation],
+) {
+  if (nameA === nameB) {
+    return 0;
+  } else if (nameA < nameB) {
+    return -1;
+  }
+  return 1;
+}
+
+function compareNameAnnotationArraysForSorting(
+  [originalPositionA, arrayA]: [
+    number,
+    Array<[string, CompleteTypeAnnotation]>,
+  ],
+  [originalPositionB, arrayB]: [
+    number,
+    Array<[string, CompleteTypeAnnotation]>,
+  ],
+) {
+  if (arrayA.length - arrayB.length !== 0) {
+    return arrayA.length - arrayB.length;
+  }
+  const nameSortedA = arrayA.sort(nameComparison);
+  const nameSortedB = arrayB.sort(nameComparison);
+  for (let i = 0; i < nameSortedA.length; i++) {
+    if (nameSortedA[i][0] === nameSortedB[i][0]) {
+      const compared = compareTypeAnnotationForSorting(
+        [originalPositionA, nameSortedA[i][1]],
+        [originalPositionB, nameSortedB[i][1]],
+      );
+      if (compared !== 0) {
+        return compared;
+      }
+      continue;
+    }
+    if (nameSortedA[i][0] < nameSortedB[i][0]) {
+      return -1;
+    }
+    return 1;
+  }
+  return 0;
+}
+
+function compareAnnotationArraysForSorting(
+  [originalPositionA, arrayA]: [number, $ReadOnlyArray<CompleteTypeAnnotation>],
+  [originalPositionB, arrayB]: [number, $ReadOnlyArray<CompleteTypeAnnotation>],
+) {
+  if (arrayA.length - arrayB.length !== 0) {
+    return arrayA.length - arrayB.length;
+  }
+  for (let i = 0; i < arrayA.length; i++) {
+    const compared = compareTypeAnnotationForSorting(
+      [originalPositionA, arrayA[i]],
+      [originalPositionB, arrayB[i]],
+    );
+    if (compared !== 0) {
+      return compared;
+    }
+    continue;
+  }
+  return 0;
+}
+
+function typeAnnotationArbitraryOrder(annotation: CompleteTypeAnnotation) {
+  switch (annotation.type) {
+    case 'AnyTypeAnnotation':
+      return 0;
+    case 'ArrayTypeAnnotation':
+      return 1;
+    case 'BooleanTypeAnnotation':
+      return 2;
+    case 'FunctionTypeAnnotation':
+      return 3;
+    case 'EventEmitterTypeAnnotation':
+      return 4;
+    case 'PromiseTypeAnnotation':
+      return 5;
+    case 'GenericObjectTypeAnnotation':
+      return 6;
+    case 'NullableTypeAnnotation':
+      return 9;
+    case 'NumberTypeAnnotation':
+      return 10;
+    case 'Int32TypeAnnotation':
+      return 11;
+    case 'DoubleTypeAnnotation':
+      return 12;
+    case 'FloatTypeAnnotation':
+      return 13;
+    case 'NumberLiteralTypeAnnotation':
+      return 14;
+    case 'ObjectTypeAnnotation':
+      return 15;
+    case 'StringLiteralUnionTypeAnnotation':
+      return 17;
+    case 'StringTypeAnnotation':
+      return 18;
+    case 'StringLiteralTypeAnnotation':
+      return 19;
+    case 'VoidTypeAnnotation':
+      return 20;
+    case 'EnumDeclaration':
+      return 21;
+    case 'EnumDeclarationWithMembers':
+      return 22;
+    case 'GenericObjectTypeAnnotation':
+      return 25;
+    case 'TypeAliasTypeAnnotation':
+      return 26;
+    case 'MixedTypeAnnotation':
+      return 27;
+    case 'ReservedTypeAnnotation':
+      return 28;
+    case 'UnionTypeAnnotation':
+      return 30;
+    default:
+      (annotation.type: empty);
+      return -1;
+  }
+}

packages/react-native-compatibility-check/src/__tests__/ErrorFormatting-test.js

@@ -0,0 +1,65 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ * @oncall react_native
+ */
+
+import {formatDiffSet} from '../ErrorFormatting.js';
+import {buildSchemaDiff, summarizeDiffSet} from '../VersionDiffing.js';
+import {incompatibleChanges, okayChanges} from './ErrorFormattingTests.js';
+import {getTestSchema} from './utilities/getTestSchema.js';
+
+describe('codegen formattedSummarizeDiffSet', () => {
+  okayChanges.forEach(([after, before]) => {
+    it(`allows a diff from ${before} to ${after}`, () => {
+      const beforeObj = getTestSchema(
+        __dirname,
+        '__fixtures__',
+        before + '.js.flow',
+      );
+
+      const afterObj = getTestSchema(
+        __dirname,
+        '__fixtures__',
+        after + '.js.flow',
+      );
+
+      const result = formatDiffSet(
+        summarizeDiffSet(buildSchemaDiff(afterObj, beforeObj)),
+      );
+
+      expect(result.status).toEqual('ok');
+
+      expect(result).toMatchSnapshot();
+    });
+  });
+
+  incompatibleChanges.forEach(([after, before]) => {
+    it(`reports a diff from ${before} to ${after}`, () => {
+      const beforeObj = getTestSchema(
+        __dirname,
+        '__fixtures__',
+        before + '.js.flow',
+      );
+
+      const afterObj = getTestSchema(
+        __dirname,
+        '__fixtures__',
+        after + '.js.flow',
+      );
+
+      const result = formatDiffSet(
+        summarizeDiffSet(buildSchemaDiff(afterObj, beforeObj)),
+      );
+
+      expect(result.status).toEqual('incompatible');
+
+      expect(result).toMatchSnapshot();
+    });
+  });
+});

packages/react-native-compatibility-check/src/__tests__/ErrorFormattingTests.js

@@ -0,0 +1,150 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ * @oncall react_native
+ */
+
+export const okayChanges = [
+  [
+    'native-module-before-after-types-removed/NativeModuleBeforeAfterTypes',
+    'native-module-before-after-types/NativeModuleBeforeAfterTypes',
+  ],
+  [
+    'native-module-get-constants/NativeModule',
+    'native-module-get-constants-added-optional-constant/NativeModule',
+  ],
+  [
+    'native-module-with-enum-from-native-changes/NativeModule',
+    'native-module-with-enum-from-native/NativeModule',
+  ],
+  [
+    'native-module-with-union/NativeModule',
+    'native-module-with-union-changes/NativeModule',
+  ],
+  [
+    'native-component-with-command/NativeComponent',
+    'native-component-with-command/NativeComponent',
+  ],
+  [
+    'native-component-with-props/NativeComponent',
+    'native-component-with-props-default-change/NativeComponent',
+  ],
+];
+
+export const incompatibleChanges = [
+  [
+    'native-module-before-after-types/NativeModuleBeforeAfterTypes',
+    'native-module-before-after-types-removed/NativeModuleBeforeAfterTypes',
+  ],
+  [
+    'native-module-before-after-types/NativeModuleBeforeAfterTypes',
+    'native-module-before-after-types-type-changed/NativeModuleBeforeAfterTypes',
+  ],
+  ['native-module/NativeModule', 'native-module-changed/NativeModule'],
+  [
+    'native-module-nested/NativeModule',
+    'native-module-nested-changed/NativeModule',
+  ],
+  [
+    'native-module-nested-optional/NativeModule',
+    'native-module-nested/NativeModule',
+  ],
+  [
+    'native-module-nested-nullable/NativeModule',
+    'native-module-nested-optional/NativeModule',
+  ],
+  [
+    'native-module-nested-optional/NativeModule',
+    'native-module-nested-changed/NativeModule',
+  ],
+  [
+    'native-module-nested-alias/NativeModule',
+    'native-module-nested-alias-changed/NativeModule',
+  ],
+  [
+    'native-module-with-dictionary/NativeModule',
+    'native-module-with-dictionary-changed/NativeModule',
+  ],
+  [
+    'native-module-with-enum-changes/NativeModule',
+    'native-module-with-enum/NativeModule',
+  ],
+  [
+    'native-module-with-enum/NativeModule',
+    'native-module-with-enum-type-changes/NativeModule',
+  ],
+  [
+    'native-module-with-enum/NativeModule',
+    'native-module-with-enum-value-changes/NativeModule',
+  ],
+
+  [
+    'native-module-with-enum-from-native/NativeModule',
+    'native-module-with-enum-from-native-changes/NativeModule',
+  ],
+  [
+    'native-module-with-enum-from-native/NativeModule',
+    'native-module-with-enum-from-native-type-changes/NativeModule',
+  ],
+  [
+    'native-module-with-enum-from-native/NativeModule',
+    'native-module-with-enum-from-native-value-changes/NativeModule',
+  ],
+  [
+    'native-module-with-eventemitter/NativeModule',
+    'native-module-with-eventemitter-changes/NativeModule',
+  ],
+  [
+    'native-module/NativeModule',
+    'native-module-with-optional-argument/NativeModule',
+  ],
+  [
+    'native-module-with-union/NativeModule',
+    'native-module-with-union-type-changes/NativeModule',
+  ],
+  [
+    'native-module-with-union-changes/NativeModule',
+    'native-module-with-union/NativeModule',
+  ],
+  [
+    'native-module-with-union-from-native/NativeModule',
+    'native-module-with-union-from-native-changes/NativeModule',
+  ],
+  [
+    'native-module-with-union/NativeModule',
+    'native-module-with-union-confusing-string-literals/NativeModule',
+  ],
+  [
+    'native-component-with-command/NativeComponent',
+    'native-component-with-command-changed/NativeComponent',
+  ],
+  [
+    'native-component-with-command-all-basic-types-arrays/NativeComponent',
+    'native-component-with-command-all-basic-types/NativeComponent',
+  ],
+  [
+    'native-component-with-command-extra-arg/NativeComponent',
+    'native-component-with-command/NativeComponent',
+  ],
+  [
+    'native-component-with-props/NativeComponent',
+    'native-component-with-props-changes/NativeComponent',
+  ],
+  [
+    'native-component-with-props/NativeComponent',
+    'native-component-with-props-added-required-prop/NativeComponent',
+  ],
+  [
+    'native-component-with-props-union-added/NativeComponent',
+    'native-component-with-props-union/NativeComponent',
+  ],
+  [
+    'native-component-with-props-array-union-added/NativeComponent',
+    'native-component-with-props-array-union/NativeComponent',
+  ],
+];

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-all-types/NativeComponent.js.flow

@@ -0,0 +1,169 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {ColorValue} from 'react-native/Libraries/StyleSheet/StyleSheet';
+import type {
+  EdgeInsetsValue,
+  PointValue,
+} from 'react-native/Libraries/StyleSheet/StyleSheetTypes';
+import type {RootTag} from 'react-native/Libraries/TurboModule/RCTExport';
+import type {
+  Double,
+  Float,
+  Int32,
+  UnsafeMixed,
+  WithDefault,
+} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeCommands from 'react-native/Libraries/Utilities/codegenNativeCommands';
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+type NativeProps = $ReadOnly<{
+  ...ViewProps,
+  bool: boolean,
+  string: string,
+  double: Double,
+  float: Float,
+  int: Int32,
+  mixed: UnsafeMixed,
+
+  optionalBool?: WithDefault<boolean, false>,
+  optionalString?: WithDefault<string, ''>,
+  optionalStringDiffDefault?: WithDefault<string, 'default'>,
+  optionalDouble?: WithDefault<Double, 0.0>,
+  optionalFloat?: WithDefault<Float, 0.0>,
+  optionalInt?: WithDefault<Int32, 0>,
+
+  reserverdEdgeInsets: EdgeInsetsValue,
+  reservedPointValue: PointValue,
+
+  stringUnion?: WithDefault<'foo' | 'bar', 'bar'>,
+  intUnion?: WithDefault<1 | 2, 1>,
+
+  nestedObject: $ReadOnly<{
+    string: string,
+    color: ColorValue,
+  }>,
+
+  nestedObjectChanged: $ReadOnly<{
+    string: boolean,
+    color: ColorValue,
+  }>,
+
+  arrayStringUnion?: WithDefault<$ReadOnlyArray<'foo' | 'bar'>, 'foo'>,
+  arrayStringUnionExtra?: WithDefault<
+    $ReadOnlyArray<'foo' | 'bar' | 'baz'>,
+    'bar',
+  >,
+
+  arrayNestedObject: $ReadOnlyArray<
+    $ReadOnly<{
+      string: string,
+      color: ColorValue,
+    }>,
+  >,
+
+  arrayNestedObjectChange: $ReadOnlyArray<
+    $ReadOnly<{
+      string: boolean,
+      color: ColorValue,
+    }>,
+  >,
+}>;
+
+type NativeType = HostComponent<NativeProps>;
+
+type Int = Int32;
+type Str = string;
+type Bool = boolean;
+type Fl = Float;
+type Dbl = Double;
+type CustomObj = {foo: string, bar: number};
+type CustomObj2 = {a: Int32, b: string};
+
+interface NativeCommands {
+  +methodInt: (viewRef: React.ElementRef<NativeType>, a: Int32) => void;
+  +methodIntString: (
+    viewRef: React.ElementRef<NativeType>,
+    a: Int32,
+    b: string,
+  ) => void;
+  +methodString: (viewRef: React.ElementRef<NativeType>, a: string) => void;
+  +methodBool: (viewRef: React.ElementRef<NativeType>, a: boolean) => void;
+  +methodFloat: (viewRef: React.ElementRef<NativeType>, a: Float) => void;
+  +methodDouble: (viewRef: React.ElementRef<NativeType>, a: Double) => void;
+
+  +methodIntAlias: (viewRef: React.ElementRef<NativeType>, a: Int) => void;
+  +methodStringAlias: (viewRef: React.ElementRef<NativeType>, a: Str) => void;
+  +methodBoolAlias: (viewRef: React.ElementRef<NativeType>, a: Bool) => void;
+  +methodFloatAlias: (viewRef: React.ElementRef<NativeType>, a: Fl) => void;
+  +methodDoubleAlias: (viewRef: React.ElementRef<NativeType>, a: Dbl) => void;
+
+  +methodIntArray: (
+    viewRef: React.ElementRef<NativeType>,
+    a: Array<Int32>,
+  ) => void;
+  +methodStringArray: (
+    viewRef: React.ElementRef<NativeType>,
+    a: Array<string>,
+  ) => void;
+  +methodBoolArray: (
+    viewRef: React.ElementRef<NativeType>,
+    a: Array<boolean>,
+  ) => void;
+  +methodFloatArray: (
+    viewRef: React.ElementRef<NativeType>,
+    a: Array<Float>,
+  ) => void;
+  +methodDoubleArray: (
+    viewRef: React.ElementRef<NativeType>,
+    a: Array<Double>,
+  ) => void;
+  +methodCustomObjArray: (
+    viewRef: React.ElementRef<NativeType>,
+    a: Array<CustomObj>,
+  ) => void;
+  +methodCustomObj2Array: (
+    viewRef: React.ElementRef<NativeType>,
+    a: Array<CustomObj2>,
+  ) => void;
+
+  +methodRootTag: (viewRef: React.ElementRef<NativeType>, a: RootTag) => void;
+}
+
+export const Commands: NativeCommands = codegenNativeCommands<NativeCommands>({
+  supportedCommands: [
+    'methodInt',
+    'methodIntString',
+    'methodString',
+    'methodBool',
+    'methodFloat',
+    'methodDouble',
+    'methodIntAlias',
+    'methodStringAlias',
+    'methodBoolAlias',
+    'methodFloatAlias',
+    'methodDoubleAlias',
+    'methodIntArray',
+    'methodStringArray',
+    'methodBoolArray',
+    'methodFloatArray',
+    'methodDoubleArray',
+    'methodCustomObjArray',
+    'methodCustomObj2Array',
+    'methodRootTag',
+  ],
+});
+
+export default codegenNativeComponent<NativeProps>(
+  'NativeComponent',
+) as NativeType;

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-command-all-basic-types-arrays/NativeComponent.js.flow

@@ -0,0 +1,60 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {
+  Double,
+  Float,
+  Int32,
+} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeCommands from 'react-native/Libraries/Utilities/codegenNativeCommands';
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+type NativeProps = $ReadOnly<{
+  ...ViewProps,
+}>;
+
+type NativeType = HostComponent<NativeProps>;
+
+interface NativeCommands {
+  +methodInt: (viewRef: React.ElementRef<NativeType>, a: Array<Int32>) => void;
+  +methodString: (
+    viewRef: React.ElementRef<NativeType>,
+    a: Array<string>,
+  ) => void;
+  +methodBool: (
+    viewRef: React.ElementRef<NativeType>,
+    a: Array<boolean>,
+  ) => void;
+  +methodFloat: (
+    viewRef: React.ElementRef<NativeType>,
+    a: Array<Float>,
+  ) => void;
+  +methodDouble: (
+    viewRef: React.ElementRef<NativeType>,
+    a: Array<Double>,
+  ) => void;
+}
+
+export const Commands: NativeCommands = codegenNativeCommands<NativeCommands>({
+  supportedCommands: [
+    'methodInt',
+    'methodString',
+    'methodBool',
+    'methodFloat',
+    'methodDouble',
+  ],
+});
+
+export default codegenNativeComponent<NativeProps>(
+  'NativeComponent',
+) as NativeType;

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-command-all-basic-types/NativeComponent.js.flow

@@ -0,0 +1,48 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {
+  Double,
+  Float,
+  Int32,
+} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeCommands from 'react-native/Libraries/Utilities/codegenNativeCommands';
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+type NativeProps = $ReadOnly<{
+  ...ViewProps,
+}>;
+
+type NativeType = HostComponent<NativeProps>;
+
+interface NativeCommands {
+  +methodInt: (viewRef: React.ElementRef<NativeType>, a: Int32) => void;
+  +methodString: (viewRef: React.ElementRef<NativeType>, a: string) => void;
+  +methodBool: (viewRef: React.ElementRef<NativeType>, a: boolean) => void;
+  +methodFloat: (viewRef: React.ElementRef<NativeType>, a: Float) => void;
+  +methodDouble: (viewRef: React.ElementRef<NativeType>, a: Double) => void;
+}
+
+export const Commands: NativeCommands = codegenNativeCommands<NativeCommands>({
+  supportedCommands: [
+    'methodInt',
+    'methodString',
+    'methodBool',
+    'methodFloat',
+    'methodDouble',
+  ],
+});
+
+export default codegenNativeComponent<NativeProps>(
+  'NativeComponent',
+) as NativeType;

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-command-changed/NativeComponent.js.flow

@@ -0,0 +1,33 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+
+import codegenNativeCommands from 'react-native/Libraries/Utilities/codegenNativeCommands';
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+type NativeProps = $ReadOnly<{
+  ...ViewProps,
+}>;
+
+type NativeType = HostComponent<NativeProps>;
+
+interface NativeCommands {
+  +methodInt: (viewRef: React.ElementRef<NativeType>, a: string) => void;
+}
+
+export const Commands: NativeCommands = codegenNativeCommands<NativeCommands>({
+  supportedCommands: ['methodInt'],
+});
+
+export default codegenNativeComponent<NativeProps>(
+  'NativeComponent',
+) as NativeType;

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-command-extra-arg/NativeComponent.js.flow

@@ -0,0 +1,38 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {Int32} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeCommands from 'react-native/Libraries/Utilities/codegenNativeCommands';
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+type NativeProps = $ReadOnly<{
+  ...ViewProps,
+}>;
+
+type NativeType = HostComponent<NativeProps>;
+
+interface NativeCommands {
+  +methodInt: (
+    viewRef: React.ElementRef<NativeType>,
+    a: Int32,
+    b: string,
+  ) => void;
+}
+
+export const Commands: NativeCommands = codegenNativeCommands<NativeCommands>({
+  supportedCommands: ['methodInt'],
+});
+
+export default codegenNativeComponent<NativeProps>(
+  'NativeComponent',
+) as NativeType;

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-command-extra-command/NativeComponent.js.flow

@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {Int32} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeCommands from 'react-native/Libraries/Utilities/codegenNativeCommands';
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+type NativeProps = $ReadOnly<{
+  ...ViewProps,
+}>;
+
+type NativeType = HostComponent<NativeProps>;
+
+interface NativeCommands {
+  +methodInt: (viewRef: React.ElementRef<NativeType>, a: Int32) => void;
+  +methodString: (viewRef: React.ElementRef<NativeType>, a: string) => void;
+}
+
+export const Commands: NativeCommands = codegenNativeCommands<NativeCommands>({
+  supportedCommands: ['methodInt', 'methodString'],
+});
+
+export default codegenNativeComponent<NativeProps>(
+  'NativeComponent',
+) as NativeType;

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-command/NativeComponent.js.flow

@@ -0,0 +1,34 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {Int32} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeCommands from 'react-native/Libraries/Utilities/codegenNativeCommands';
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+type NativeProps = $ReadOnly<{
+  ...ViewProps,
+}>;
+
+type NativeType = HostComponent<NativeProps>;
+
+interface NativeCommands {
+  +methodInt: (viewRef: React.ElementRef<NativeType>, a: Int32) => void;
+}
+
+export const Commands: NativeCommands = codegenNativeCommands<NativeCommands>({
+  supportedCommands: ['methodInt'],
+});
+
+export default codegenNativeComponent<NativeProps>(
+  'NativeComponent',
+) as NativeType;

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-props-added-optional-prop/NativeComponent.js.flow

@@ -0,0 +1,30 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {
+  Int32,
+  WithDefault,
+} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+  text: string,
+  backgroundColor?: WithDefault<string, 'transparent'>,
+  height?: WithDefault<Int32, 100>,
+  width?: WithDefault<Int32, 100>,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-props-added-required-prop/NativeComponent.js.flow

@@ -0,0 +1,30 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {
+  Int32,
+  WithDefault,
+} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+  text: string,
+  backgroundColor?: WithDefault<string, 'transparent'>,
+  height?: WithDefault<Int32, 100>,
+  width: Int32,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-props-all-types/NativeComponent.js.flow

@@ -0,0 +1,39 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {
+  Double,
+  Float,
+  Int32,
+  WithDefault,
+} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+  bool: boolean,
+  string: string,
+  double: Double,
+  float: Float,
+  int: Int32,
+  stringUnion: WithDefault<'foo' | 'bar', 'bar'>,
+  intUnion: WithDefault<1 | 2, 1>,
+  mixed: mixed,
+
+  backgroundColor?: WithDefault<string, 'transparent'>,
+  height?: WithDefault<Int32, 100>,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-props-array-union-added/NativeComponent.js.flow

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {WithDefault} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+  sizes?: WithDefault<$ReadOnlyArray<'small' | 'large' | 'huge'>, 'small'>,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-props-array-union/NativeComponent.js.flow

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {WithDefault} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+  sizes?: WithDefault<$ReadOnlyArray<'small' | 'large'>, 'small'>,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-props-changes/NativeComponent.js.flow

@@ -0,0 +1,29 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {
+  Int32,
+  WithDefault,
+} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+  text: Int32,
+  backgroundColor?: WithDefault<string, 'transparent'>,
+  height?: WithDefault<Int32, 100>,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-props-default-change/NativeComponent.js.flow

@@ -0,0 +1,29 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {
+  Int32,
+  WithDefault,
+} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+  text: string,
+  backgroundColor?: WithDefault<string, 'white'>,
+  height?: WithDefault<Int32, 100>,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-props-nested-object-added-optional-key/NativeComponent.js.flow

@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {
+  Float,
+  Int32,
+  WithDefault,
+} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+  text: string,
+  backgroundColor?: WithDefault<string, 'transparent'>,
+  height?: WithDefault<Int32, 100>,
+  pins: $ReadOnly<{
+    x: Float,
+    y: Float,
+    color?: WithDefault<string, 'red'>,
+  }>,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-props-nested-object-added-required-key/NativeComponent.js.flow

@@ -0,0 +1,35 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {
+  Float,
+  Int32,
+  WithDefault,
+} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+  text: string,
+  backgroundColor?: WithDefault<string, 'transparent'>,
+  height?: WithDefault<Int32, 100>,
+  pins: $ReadOnly<{
+    x: Float,
+    y: Float,
+    color: string,
+  }>,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-props-nested-object/NativeComponent.js.flow

@@ -0,0 +1,34 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {
+  Float,
+  Int32,
+  WithDefault,
+} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+  text: string,
+  backgroundColor?: WithDefault<string, 'transparent'>,
+  height?: WithDefault<Int32, 100>,
+  pins: $ReadOnly<{
+    x: Float,
+    y: Float,
+  }>,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-props-union-added/NativeComponent.js.flow

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {WithDefault} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+  size?: WithDefault<'small' | 'large' | 'huge', 'small'>,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-props-union/NativeComponent.js.flow

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {WithDefault} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+  size?: WithDefault<'small' | 'large', 'small'>,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component-with-props/NativeComponent.js.flow

@@ -0,0 +1,29 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+import type {
+  Int32,
+  WithDefault,
+} from 'react-native/Libraries/Types/CodegenTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+  text: string,
+  backgroundColor?: WithDefault<string, 'transparent'>,
+  height?: WithDefault<Int32, 100>,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-component/NativeComponent.js.flow

@@ -0,0 +1,22 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ */
+
+import type {HostComponent} from 'react-native';
+import type {ViewProps} from 'react-native/Libraries/Components/View/ViewPropTypes';
+
+import codegenNativeComponent from 'react-native/Libraries/Utilities/codegenNativeComponent';
+
+export type Props = $ReadOnly<{
+  ...ViewProps,
+}>;
+
+export default (codegenNativeComponent<Props>(
+  'NativeComponent',
+): HostComponent<Props>);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-before-after-types-removed/NativeModuleBeforeAfterTypes.js.flow

@@ -0,0 +1,33 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+/* eslint-disable no-unused-vars */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+type SimpleObject = {||};
+
+type BeforeMismatchGeneric<T> = {||};
+
+type BeforeMatchingGeneric<T> = {||};
+type AfterMatchingGeneric<T> = {||};
+
+export interface Spec extends TurboModule {
+  +simpleObject: (a: SimpleObject) => void;
+  +beforeMismatchGeneric: <T>(a: BeforeMismatchGeneric<T>) => void;
+
+  +beforeMatchingGeneric: <T>(a: BeforeMatchingGeneric<T>) => void;
+  +afterMatchingGeneric: <T>(a: AfterMatchingGeneric<T>) => void;
+}
+
+(TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-before-after-types-type-changed/NativeModuleBeforeAfterTypes.js.flow

@@ -0,0 +1,73 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+/* eslint-disable no-unused-vars */
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+type SimpleObject = {||};
+
+type BeforeMismatchGeneric<T> = {||};
+type AfterMismatchGeneric<Foo> = {||};
+
+type BeforeMatchingGeneric<T> = {||};
+type AfterMatchingGeneric<T> = {||};
+
+type BooleanType = boolean;
+type StringType = string;
+
+type SimpleFunction = (a: string) => string;
+type SimpleFunction2 = (a: string) => number;
+type SimpleFunction3 = (foo: string) => string;
+type SimpleFunction4 = (a: number) => string;
+
+type SimpleUnion = 'str1' | 'str2';
+type SimpleUnionLonger = 'str1' | 'str2' | 'str3';
+type SimpleUnion2 = 4 | 5;
+type SimpleUnion3 = {} | {key: 'value'};
+type SimpleUnion4 = BooleanType | StringType | SimpleObject;
+
+type FunctionReferencingUnion = (a: SimpleUnion) => void;
+type FunctionReferencingUnion2 = (a: SimpleUnion2) => void;
+
+type SimpleArray = Array<string>;
+// changed from Array<number> to Array<string>
+type SimpleArrayChange = Array<string>;
+
+export interface Spec extends TurboModule {
+    +exampleFunction: (a: SimpleObject) => void;
+    +simpleObject: (a: SimpleObject) => void;
+    +beforeMismatchGeneric: <T>(a: BeforeMismatchGeneric<T>) => void;
+    +afterMismatchGeneric: <Foo>(a: AfterMismatchGeneric<Foo>) => void;
+
+    +beforeMatchingGeneric: <T>(a: BeforeMatchingGeneric<T>) => void;
+    +afterMatchingGeneric: <T>(a: AfterMatchingGeneric<T>) => void;
+
+    +booleanType: (a: BooleanType) => void;
+    +stringType: (a: StringType) => void;
+
+    +simpleFunction: (a: string) => string;
+    +simpleFunction2: (a: string) => number;
+    +simpleFunction3: (foo: string) => string;
+    +simpleFunction4: (a: number) => string;
+
+    +simpleUnion: (a: SimpleUnion) => void;
+    +simpleUnionLonger: (a: SimpleUnionLonger) => void;
+    +simpleUnion2: (a: SimpleUnion2) => void;
+    +simpleUnion3: (a: SimpleUnion3) => void;
+    +simpleUnion4: (a: SimpleUnion4) => void;
+
+    +simpleArray: (a: SimpleArray) => void;
+    +simpleArrayChange: (a: SimpleArrayChange) => void;
+  }
+
+  (TurboModuleRegistry.getEnforcing<Spec>(
+    'NativeModuleTest',
+  ): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-before-after-types/NativeModuleBeforeAfterTypes.js.flow

@@ -0,0 +1,66 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+/* eslint-disable no-unused-vars */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+type SimpleObject = {};
+
+type BeforeMismatchGeneric<T> = {};
+type AfterMismatchGeneric<Foo> = {};
+
+type BeforeMatchingGeneric<T> = {};
+type AfterMatchingGeneric<T> = {};
+
+type BooleanType = boolean;
+type StringType = string;
+
+type SimpleUnion = 'str1' | 'str2';
+type SimpleUnionLonger = 'str1' | 'str2' | 'str3';
+type SimpleUnion2 = 4 | 5;
+type SimpleUnion3 = {} | {key: 'value'};
+type SimpleUnion4 = BooleanType | StringType | SimpleObject;
+
+type SimpleArray = Array<string>;
+type SimpleArrayChange = Array<number>;
+
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: SimpleObject) => void;
+  +simpleObject: (a: SimpleObject) => void;
+  +beforeMismatchGeneric: <T>(a: BeforeMismatchGeneric<T>) => void;
+  +afterMismatchGeneric: <Foo>(a: AfterMismatchGeneric<Foo>) => void;
+
+  +beforeMatchingGeneric: <T>(a: BeforeMatchingGeneric<T>) => void;
+  +afterMatchingGeneric: <T>(a: AfterMatchingGeneric<T>) => void;
+
+  +booleanType: (a: BooleanType) => void;
+  +stringType: (a: StringType) => void;
+
+  +simpleFunction: (a: string) => string;
+  +simpleFunction2: (a: string) => number;
+  +simpleFunction3: (foo: string) => string;
+  +simpleFunction4: (a: number) => string;
+
+  +simpleUnion: (a: SimpleUnion) => void;
+  +simpleUnionLonger: (a: SimpleUnionLonger) => void;
+  +simpleUnion2: (a: SimpleUnion2) => void;
+  +simpleUnion3: (a: SimpleUnion3) => void;
+  +simpleUnion4: (a: SimpleUnion4) => void;
+
+  +simpleArray: (a: SimpleArray) => void;
+  +simpleArrayChange: (a: SimpleArrayChange) => void;
+}
+
+(TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-changed/NativeModule.js.flow

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: string,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-get-constants-added-optional-constant-readonly/NativeModule.js.flow

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => $ReadOnly<{
+    constant?: string,
+  }>;
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-get-constants-added-optional-constant/NativeModule.js.flow

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => {
+    +constant?: string,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-get-constants-added-required-constant-readonly/NativeModule.js.flow

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => $ReadOnly<{
+    constant: string,
+  }>;
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-get-constants-added-required-constant/NativeModule.js.flow

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => {
+    +constant: string,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-get-constants-readonly/NativeModule.js.flow

@@ -0,0 +1,22 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => $ReadOnly<{}>;
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-get-constants/NativeModule.js.flow

@@ -0,0 +1,22 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => {};
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-nested-alias-changed/NativeModule.js.flow

@@ -0,0 +1,23 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+type MyType = () => Promise<number>;
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: MyType, b: number) => void;
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-nested-alias/NativeModule.js.flow

@@ -0,0 +1,23 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+type MyType = () => Promise<string>;
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: MyType, b: number) => void;
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-nested-changed/NativeModule.js.flow

@@ -0,0 +1,32 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (
+    a: {
+      a1: string,
+      a2: number,
+      a3: string,
+      ...
+    },
+    b: number,
+  ) => void;
+  +getConstants: () => {
+    +exampleConstant: string,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-nested-nullable/NativeModule.js.flow

@@ -0,0 +1,32 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (
+    a: ?{
+      a1: string,
+      a2?: number,
+      a3: string,
+      ...
+    },
+    b: number,
+  ) => void;
+  +getConstants: () => {
+    +exampleConstant: string,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-nested-optional/NativeModule.js.flow

@@ -0,0 +1,32 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (
+    a: {
+      a1: string,
+      a2?: number,
+      a3: string,
+      ...
+    },
+    b: number,
+  ) => void;
+  +getConstants: () => {
+    +exampleConstant: string,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-nested/NativeModule.js.flow

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (
+    a: {
+      a1: string,
+      a2: number,
+      ...
+    },
+    b: number,
+  ) => void;
+  +getConstants: () => {
+    +exampleConstant: string,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-type-diffing-types/NativeTypeDiffingTypes.js.flow

@@ -0,0 +1,218 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ */
+
+/* eslint-disable no-unused-vars */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+import type {UnsafeObject} from 'react-native/Libraries/Types/CodegenTypes';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+type StringLiteral0 = 'foo';
+type StringLiteral1 = 'bar';
+
+type NumericLiteral0 = 1;
+type NumericLiteral1 = 2;
+
+type StringLiteralUnion0 = 'a' | 'b' | 'c';
+type StringLiteralUnion1 = 'a' | 'b' | 'c' | 'd';
+type StringLiteralUnion2 = 'a' | 'x' | 'c';
+
+type Tuple0 = [string, number];
+type Tuple1 = [string, number, number];
+type Tuple2 = [number, number];
+
+type ReferencedType = {...};
+type ReferencedType2 = {...};
+type ReferencedType3 = {prop0: string, ...};
+
+type ReferenceType = ReferencedType;
+type ReferenceType2 = ReferencedType2;
+type ReferenceType3 = ReferencedType3;
+type ReferenceGeneric<T> = ReferencedType;
+type ReferenceGeneric2<T, X> = ReferencedType;
+
+type ObjectTypeWithProps = {
+  prop1: string,
+  prop2: number,
+  prop3: boolean,
+  ...
+};
+type ObjectTypeLessProps = {
+  prop1: string,
+  prop3: boolean,
+  ...
+};
+
+type ObjectTypeWithDifferentProps = {
+  prop0: string,
+  prop4: number,
+  prop5: boolean,
+  ...
+};
+
+type ObjectTypeWithNesting = {
+  prop1: {
+    subprop1: string,
+    subprop2: number,
+    ...
+  },
+  prop2: number,
+  ...
+};
+type ObjectTypeWithChanges = {
+  prop1: number,
+  prop2: {
+    subprop1: string,
+    subprp2: number,
+    ...
+  },
+  ...
+};
+type ObjectTypeWithNestedChanges = {
+  prop1: {
+    subprop1: string,
+    subprop2: string,
+    ...
+  },
+  prop2: number,
+  ...
+};
+type ObjectTypeWithTwoOptionals = {
+  prop1?: string,
+  prop2: number,
+  prop3?: boolean,
+  ...
+};
+type ObjectTypeWithOptionalNestedChange = {
+  prop1?: {
+    subprop1: string,
+    subprop2: number,
+    subprop3: string,
+    ...
+  },
+  prop2: number,
+  ...
+};
+
+type NonNullableType = Object;
+type NullableType = ?Object;
+
+type GenericObjectType = Object;
+type UnsafeObjectType = UnsafeObject;
+
+type OptionalTypeLessProps = ?{
+  prop1: string,
+  prop3: boolean,
+  ...
+};
+
+type ObjectTypeLiteral1 = {
+  prop1: number,
+  prop2: {
+    subprop1: string,
+    subprp2: number,
+  },
+};
+
+type ObjectTypeLiteral2 = {
+  prop1: number,
+  prop2: {
+    subprop1: string,
+    subprp2: number,
+  },
+};
+
+type ObjectTypeLiteral1TypeAlias = ObjectTypeLiteral1;
+type ObjectTypeLiteral2TypeAlias = ObjectTypeLiteral2;
+
+type MapWithKey = {[a: string]: ?number};
+type MapWithKey2 = {[a: string]: ?string};
+
+enum Enum {
+  A = 1,
+  B = 2,
+  C = 3,
+  D = 4,
+}
+enum EnumWithTypeChange {
+  A = '1',
+  B = '2',
+  C = '3',
+  D = '4',
+}
+enum EnumWithRemoval {
+  A = 1,
+  B = 2,
+  C = 3,
+}
+enum EnumWithValueChange {
+  A = 1,
+  B = 2,
+  C = 3,
+  D = 14,
+}
+
+enum EnumUnsorted {
+  C = 3,
+  D = 4,
+  B = 2,
+  A = 1,
+}
+
+export interface Spec extends TurboModule {
+  +stringLiteral0: (a: StringLiteral0) => void;
+  +stringLiteral1: (a: StringLiteral1) => void;
+
+  +numericLiteral0: (a: NumericLiteral0) => void;
+  +numericLiteral1: (a: NumericLiteral1) => void;
+
+  +stringLiteralUnion0: (a: StringLiteralUnion0) => void;
+  +stringLiteralUnion1: (a: StringLiteralUnion1) => void;
+  +stringLiteralUnion2: (a: StringLiteralUnion2) => void;
+
+  +referenceType: (a: ReferenceType) => void;
+  +referenceType2: (a: ReferenceType2) => void;
+  +referenceType3: (a: ReferenceType3) => void;
+
+  +referenceGeneric: <T>(a: ReferenceGeneric<T>) => void;
+  +referenceGeneric2: <T, X>(a: ReferenceGeneric2<T, X>) => void;
+
+  +objectTypeWithProps: (a: ObjectTypeWithProps) => void;
+  +objectTypeLessProps: (a: ObjectTypeLessProps) => void;
+  +objectTypeWithDifferentProps: (a: ObjectTypeWithDifferentProps) => void;
+  +objectTypeWithNesting: (a: ObjectTypeWithNesting) => void;
+  +objectTypeWithChanges: (a: ObjectTypeWithChanges) => void;
+  +objectTypeWithNestedChanges: (a: ObjectTypeWithNestedChanges) => void;
+  +objectTypeWithTwoOptionals: (a: ObjectTypeWithTwoOptionals) => void;
+  +objectTypeWithOptionalNestedChange: (a: ObjectTypeWithOptionalNestedChange) => void;
+  +nonNullableType: (a: NonNullableType) => void;
+  +nullableType: (a: NullableType) => void;
+  +genericObjectType: (a: GenericObjectType) => void;
+  +unsafeObjectType: (a: UnsafeObjectType) => void;
+  +optionalTypeLessProps: (a: OptionalTypeLessProps) => void;
+  +objectTypeLiteral1: (a: ObjectTypeLiteral1) => void;
+  +objectTypeLiteral2: (a: ObjectTypeLiteral2) => void;
+  +objectTypeLiteral1TypeAlias: (a: ObjectTypeLiteral1TypeAlias) => void;
+  +objectTypeLiteral2TypeAlias: (a: ObjectTypeLiteral2TypeAlias) => void;
+  +genericObjectType: (a: Object) => void;
+
+  +mapWithKey: (a: MapWithKey) => void;
+  +mapWithKey2: (a: MapWithKey2) => void;
+
+  +enum: (a: Enum) => void;
+  +enumWithTypeChange: (a: EnumWithTypeChange) => void;
+  +enumWithRemoval: (a: EnumWithRemoval) => void;
+  +enumWithValueChange: (a: EnumWithValueChange) => void;
+  +enumUnsorted: (a: EnumUnsorted) => void;
+}
+
+(TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-dictionary-changed/NativeModule.js.flow

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: {[key: string]: string}, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: number,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-dictionary/NativeModule.js.flow

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: {[key: string]: number}, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: number,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-enum-changes/NativeModule.js.flow

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+enum TestEnum {
+  A = 1,
+  B = 2,
+  C = 3,
+  D = 4,
+}
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: TestEnum, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: number,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-enum-from-native-changes/NativeModule.js.flow

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+enum TestEnum {
+  A = 1,
+  B = 2,
+  C = 3,
+  D = 4,
+}
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: TestEnum,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-enum-from-native-type-changes/NativeModule.js.flow

@@ -0,0 +1,30 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+enum TestEnum {
+  A = '1',
+  B = '2',
+  C = '3',
+}
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: TestEnum,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-enum-from-native-value-changes/NativeModule.js.flow

@@ -0,0 +1,30 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+enum TestEnum {
+  A = 1,
+  B = 13,
+  C = 3,
+}
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: TestEnum,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-enum-from-native/NativeModule.js.flow

@@ -0,0 +1,30 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+enum TestEnum {
+  A = 1,
+  B = 2,
+  C = 3,
+}
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: TestEnum,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-enum-type-changes/NativeModule.js.flow

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+enum TestEnum {
+  A = '1',
+  B = '2',
+  C = '3',
+  D = '4',
+}
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: TestEnum, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: number,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-enum-value-changes/NativeModule.js.flow

@@ -0,0 +1,30 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+enum TestEnum {
+  A = 1,
+  B = 13,
+  C = 3,
+}
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: TestEnum, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: number,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-enum/NativeModule.js.flow

@@ -0,0 +1,30 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+enum TestEnum {
+  A = 1,
+  B = 2,
+  C = 3,
+}
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: TestEnum, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: number,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-eventemitter-changes/NativeModule.js.flow

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+import type {EventEmitter} from 'react-native/Libraries/Types/CodegenTypes';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export type ObjectStruct = {
+  a: number,
+  b: string,
+  c?: ?string,
+};
+
+export interface Spec extends TurboModule {
+  onPress: EventEmitter<string>;
+  onClick: EventEmitter<number>;
+  onChange: EventEmitter<ObjectStruct[]>;
+  onSubmit: EventEmitter<ObjectStruct>;
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-eventemitter/NativeModule.js.flow

@@ -0,0 +1,31 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+import type {EventEmitter} from 'react-native/Libraries/Types/CodegenTypes';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export type ObjectStruct = {
+  a: number,
+  b: string,
+  c?: ?string,
+};
+
+export interface Spec extends TurboModule {
+  onPress: EventEmitter<void>;
+  onClick: EventEmitter<string>;
+  onChange: EventEmitter<ObjectStruct>;
+  onSubmit: EventEmitter<ObjectStruct[]>;
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-optional-argument/NativeModule.js.flow

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number, c?: number) => void;
+  +getConstants: () => {
+    +exampleConstant: number,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-union-changes/NativeModule.js.flow

@@ -0,0 +1,26 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+type testUnion = 'a' | 'b' | 'c' | 'd';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: testUnion, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: number,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-union-confusing-string-literals/NativeModule.js.flow

@@ -0,0 +1,26 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+type testUnion = 'a' | '0' | '1' | 'a long string';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: testUnion, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: number,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-union-from-native-changes/NativeModule.js.flow

@@ -0,0 +1,26 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+type testUnion = 'a' | 'b' | 'c' | 'd';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: testUnion,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-union-from-native/NativeModule.js.flow

@@ -0,0 +1,26 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+type testUnion = 'a' | 'b' | 'c';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: testUnion,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-union-type-changes/NativeModule.js.flow

@@ -0,0 +1,26 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+type testUnion = 1 | 2 | 3;
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: testUnion, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: number,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module-with-union/NativeModule.js.flow

@@ -0,0 +1,26 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+type testUnion = 'a' | 'b' | 'c';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: testUnion, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: number,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__fixtures__/native-module/NativeModule.js.flow

@@ -0,0 +1,24 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow
+ * @format
+ */
+
+import type {TurboModule} from 'react-native/Libraries/TurboModule/RCTExport';
+
+import * as TurboModuleRegistry from 'react-native/Libraries/TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +exampleFunction: (a: string, b: number) => void;
+  +getConstants: () => {
+    +exampleConstant: number,
+  };
+}
+
+export default (TurboModuleRegistry.getEnforcing<Spec>(
+  'NativeModuleTest',
+): Spec);

packages/react-native-compatibility-check/src/__tests__/__snapshots__/ErrorFormatting-test.js.snap

@@ -0,0 +1,792 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`codegen formattedSummarizeDiffSet allows a diff from native-component-with-command/NativeComponent to native-component-with-command/NativeComponent 1`] = `
+Object {
+  "incompatibilityReport": Object {},
+  "status": "ok",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet allows a diff from native-component-with-props-default-change/NativeComponent to native-component-with-props/NativeComponent 1`] = `
+Object {
+  "incompatibilityReport": Object {},
+  "status": "ok",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet allows a diff from native-module-before-after-types/NativeModuleBeforeAfterTypes to native-module-before-after-types-removed/NativeModuleBeforeAfterTypes 1`] = `
+Object {
+  "incompatibilityReport": Object {},
+  "status": "ok",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet allows a diff from native-module-get-constants-added-optional-constant/NativeModule to native-module-get-constants/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {},
+  "status": "ok",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet allows a diff from native-module-with-enum-from-native/NativeModule to native-module-with-enum-from-native-changes/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {},
+  "status": "ok",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet allows a diff from native-module-with-union-changes/NativeModule to native-module-with-union/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {},
+  "status": "ok",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-component-with-command/NativeComponent to native-component-with-command-extra-arg/NativeComponent 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeComponent": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeComponent: Object contained a property with a type mismatch
+  -- methodInt: has conflicting type changes
+      --new: (a: int, b: string)=>void
+      --old: (a: int)=>void
+      Function types have differing length of arguments
+          --new: (a: int, b: string)=>void
+          --old: (a: int)=>void",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-component-with-command-all-basic-types/NativeComponent to native-component-with-command-all-basic-types-arrays/NativeComponent 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeComponent": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeComponent: Object contained a property with a type mismatch
+  -- methodInt: has conflicting type changes
+      --new: (a: Array<int>)=>void
+      --old: (a: int)=>void
+      Parameter at index 0 did not match
+          --new: (a: Array<int>)=>void
+          --old: (a: int)=>void
+          Type annotations are not the same.
+              --new: Array<int>
+              --old: int",
+        },
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeComponent: Object contained a property with a type mismatch
+  -- methodString: has conflicting type changes
+      --new: (a: Array<string>)=>void
+      --old: (a: string)=>void
+      Parameter at index 0 did not match
+          --new: (a: Array<string>)=>void
+          --old: (a: string)=>void
+          Type annotations are not the same.
+              --new: Array<string>
+              --old: string",
+        },
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeComponent: Object contained a property with a type mismatch
+  -- methodBool: has conflicting type changes
+      --new: (a: Array<boolean>)=>void
+      --old: (a: boolean)=>void
+      Parameter at index 0 did not match
+          --new: (a: Array<boolean>)=>void
+          --old: (a: boolean)=>void
+          Type annotations are not the same.
+              --new: Array<boolean>
+              --old: boolean",
+        },
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeComponent: Object contained a property with a type mismatch
+  -- methodFloat: has conflicting type changes
+      --new: (a: Array<float>)=>void
+      --old: (a: float)=>void
+      Parameter at index 0 did not match
+          --new: (a: Array<float>)=>void
+          --old: (a: float)=>void
+          Type annotations are not the same.
+              --new: Array<float>
+              --old: float",
+        },
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeComponent: Object contained a property with a type mismatch
+  -- methodDouble: has conflicting type changes
+      --new: (a: Array<double>)=>void
+      --old: (a: double)=>void
+      Parameter at index 0 did not match
+          --new: (a: Array<double>)=>void
+          --old: (a: double)=>void
+          Type annotations are not the same.
+              --new: Array<double>
+              --old: double",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-component-with-command-changed/NativeComponent to native-component-with-command/NativeComponent 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeComponent": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeComponent: Object contained a property with a type mismatch
+  -- methodInt: has conflicting type changes
+      --new: (a: int)=>void
+      --old: (a: string)=>void
+      Parameter at index 0 did not match
+          --new: (a: int)=>void
+          --old: (a: string)=>void
+          Type annotations are not the same.
+              --new: int
+              --old: string",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-component-with-props-added-required-prop/NativeComponent to native-component-with-props/NativeComponent 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeComponent": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "removedProps",
+          "message": "NativeComponent: Object removed required properties expected by native
+  -- width",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-component-with-props-array-union/NativeComponent to native-component-with-props-array-union-added/NativeComponent 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeComponent": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "addedUnionCases",
+          "message": "NativeComponent.sizes: Union added items, but native will not expect/support them
+  -- position 3 huge",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-component-with-props-changes/NativeComponent to native-component-with-props/NativeComponent 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeComponent": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeComponent: Object contained a property with a type mismatch
+  -- text: has conflicting type changes
+      --new: string
+      --old: int
+      Type annotations are not the same.
+          --new: string
+          --old: int",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-component-with-props-union/NativeComponent to native-component-with-props-union-added/NativeComponent 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeComponent": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "addedUnionCases",
+          "message": "NativeComponent.size: Union added items, but native will not expect/support them
+  -- position 3 huge",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-before-after-types-removed/NativeModuleBeforeAfterTypes to native-module-before-after-types/NativeModuleBeforeAfterTypes 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModuleBeforeAfterTypes": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "addedProps",
+          "message": "NativeModuleTest: Object added required properties, which native will not provide
+  -- afterMismatchGeneric
+  -- booleanType
+  -- exampleFunction
+  -- simpleArray
+  -- simpleArrayChange
+  -- simpleFunction
+  -- simpleFunction2
+  -- simpleFunction3
+  -- simpleFunction4
+  -- simpleUnion
+  -- simpleUnion2
+  -- simpleUnion3
+  -- simpleUnion4
+  -- simpleUnionLonger
+  -- stringType",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-before-after-types-type-changed/NativeModuleBeforeAfterTypes to native-module-before-after-types/NativeModuleBeforeAfterTypes 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModuleBeforeAfterTypes": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeModuleTest: Object contained a property with a type mismatch
+  -- simpleArrayChange: has conflicting type changes
+      --new: (a: Array<number>)=>void
+      --old: (a: Array<string>)=>void
+      Parameter at index 0 did not match
+          --new: (a: Array<number>)=>void
+          --old: (a: Array<string>)=>void
+          Type annotations are not the same.
+              --new: number
+              --old: string",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-changed/NativeModule to native-module/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeModuleTest: Object contained a property with a type mismatch
+  -- getConstants: has conflicting type changes
+      --new: ()=>{exampleConstant: number}
+      --old: ()=>{exampleConstant: string}
+      Function return types do not match
+          --new: ()=>{exampleConstant: number}
+          --old: ()=>{exampleConstant: string}
+          Object contained a property with a type mismatch
+              -- exampleConstant: has conflicting type changes
+                  --new: number
+                  --old: string
+                  Type annotations are not the same.
+                      --new: number
+                      --old: string",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-nested/NativeModule to native-module-nested-optional/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "optionalProps",
+          "message": "NativeModuleTest.exampleFunction parameter 0: Property made optional, but native requires it
+  -- a2",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-nested-alias-changed/NativeModule to native-module-nested-alias/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeModuleTest: Object contained a property with a type mismatch
+  -- exampleFunction: has conflicting type changes
+      --new: (a: ()=>Promise<string>, b: number)=>void
+      --old: (a: ()=>Promise<number>, b: number)=>void
+      Parameter at index 0 did not match
+          --new: (a: ()=>Promise<string>, b: number)=>void
+          --old: (a: ()=>Promise<number>, b: number)=>void
+          Function return types do not match
+              --new: ()=>Promise<string>
+              --old: ()=>Promise<number>
+              Type annotations are not the same.
+                  --new: string
+                  --old: number",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-nested-changed/NativeModule to native-module-nested/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "removedProps",
+          "message": "NativeModuleTest.exampleFunction parameter 0: Object removed required properties expected by native
+  -- a3",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-nested-changed/NativeModule to native-module-nested-optional/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "optionalProps",
+          "message": "NativeModuleTest.exampleFunction parameter 0: Property made optional, but native requires it
+  -- a2",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-nested-optional/NativeModule to native-module-nested-nullable/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "nullableOfNonNull",
+          "message": "NativeModuleTest.exampleFunction parameter 0: Type made nullable, but native requires it
+  --new: ?{a1: string, a2?: number, a3: string}
+  --old: {a1: string, a2?: number, a3: string}",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-with-dictionary-changed/NativeModule to native-module-with-dictionary/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeModuleTest: Object contained a property with a type mismatch
+  -- exampleFunction: has conflicting type changes
+      --new: (a: {[string]: number, b: number)=>void
+      --old: (a: {[string]: string, b: number)=>void
+      Parameter at index 0 did not match
+          --new: (a: {[string]: number, b: number)=>void
+          --old: (a: {[string]: string, b: number)=>void
+          Type annotations are not the same.
+              --new: number
+              --old: string",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-with-enum/NativeModule to native-module-with-enum-changes/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "addedEnumCases",
+          "message": "NativeModuleTest.exampleFunction parameter 0: Enum added items, but native will not expect/support them
+  -- Member D",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-with-enum-from-native-changes/NativeModule to native-module-with-enum-from-native/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "removedEnumCases",
+          "message": "NativeModuleTest.getConstants.exampleConstant: Enum removed items, but native may still provide them
+  -- Member D",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-with-enum-from-native-type-changes/NativeModule to native-module-with-enum-from-native/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeModuleTest: Object contained a property with a type mismatch
+  -- getConstants: has conflicting type changes
+      --new: ()=>{exampleConstant: Enum<number>}
+      --old: ()=>{exampleConstant: Enum<string>}
+      Function return types do not match
+          --new: ()=>{exampleConstant: Enum<number>}
+          --old: ()=>{exampleConstant: Enum<string>}
+          Object contained a property with a type mismatch
+              -- exampleConstant: has conflicting type changes
+                  --new: Enum<number>
+                  --old: Enum<string>
+                  EnumDeclaration member types are not the same
+                      --new: Enum<number>
+                      --old: Enum<string>",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-with-enum-from-native-value-changes/NativeModule to native-module-with-enum-from-native/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeModuleTest: Object contained a property with a type mismatch
+  -- getConstants: has conflicting type changes
+      --new: ()=>{exampleConstant: Enum<number>}
+      --old: ()=>{exampleConstant: Enum<number>}
+      Function return types do not match
+          --new: ()=>{exampleConstant: Enum<number>}
+          --old: ()=>{exampleConstant: Enum<number>}
+          Object contained a property with a type mismatch
+              -- exampleConstant: has conflicting type changes
+                  --new: Enum<number>
+                  --old: Enum<number>
+                  Enum types do not match
+                      --new: Enum<number> {A = 1, B = 2, C = 3}
+                      --old: Enum<number> {A = 1, B = 13, C = 3}
+                      Enum contained a member with a type mismatch
+                          -- Member B: has conflicting changes
+                              --new: 2
+                              --old: 13
+                              Numeric literals are not equal
+                                  --new: 2
+                                  --old: 13",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-with-enum-type-changes/NativeModule to native-module-with-enum/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeModuleTest: Object contained a property with a type mismatch
+  -- exampleFunction: has conflicting type changes
+      --new: (a: Enum<number>, b: number)=>void
+      --old: (a: Enum<string>, b: number)=>void
+      Parameter at index 0 did not match
+          --new: (a: Enum<number>, b: number)=>void
+          --old: (a: Enum<string>, b: number)=>void
+          EnumDeclaration member types are not the same
+              --new: Enum<number>
+              --old: Enum<string>",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-with-enum-value-changes/NativeModule to native-module-with-enum/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeModuleTest: Object contained a property with a type mismatch
+  -- exampleFunction: has conflicting type changes
+      --new: (a: Enum<number>, b: number)=>void
+      --old: (a: Enum<number>, b: number)=>void
+      Parameter at index 0 did not match
+          --new: (a: Enum<number>, b: number)=>void
+          --old: (a: Enum<number>, b: number)=>void
+          Enum types do not match
+              --new: Enum<number> {A = 1, B = 2, C = 3}
+              --old: Enum<number> {A = 1, B = 13, C = 3}
+              Enum contained a member with a type mismatch
+                  -- Member B: has conflicting changes
+                      --new: 2
+                      --old: 13
+                      Numeric literals are not equal
+                          --new: 2
+                          --old: 13",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-with-eventemitter-changes/NativeModule to native-module-with-eventemitter/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeModuleTest: Object contained properties with type mismatches
+  -- onChange: has conflicting type changes
+      --new: EventEmitter<ObjectStruct>
+      --old: EventEmitter<Array<ObjectStruct>>
+      EventEmitter eventTypes are not equivalent
+          --new: EventEmitter<ObjectStruct>
+          --old: EventEmitter<Array<ObjectStruct>>
+          Type annotations are not the same.
+              --new: {a: number, b: string, c?: ?string}
+              --old: Array<ObjectStruct>
+  -- onClick: has conflicting type changes
+      --new: EventEmitter<string>
+      --old: EventEmitter<number>
+      EventEmitter eventTypes are not equivalent
+          --new: EventEmitter<string>
+          --old: EventEmitter<number>
+          Type annotations are not the same.
+              --new: string
+              --old: number
+  -- onPress: has conflicting type changes
+      --new: EventEmitter<void>
+      --old: EventEmitter<string>
+      EventEmitter eventTypes are not equivalent
+          --new: EventEmitter<void>
+          --old: EventEmitter<string>
+          Type annotations are not the same.
+              --new: void
+              --old: string
+  -- onSubmit: has conflicting type changes
+      --new: EventEmitter<Array<ObjectStruct>>
+      --old: EventEmitter<ObjectStruct>
+      EventEmitter eventTypes are not equivalent
+          --new: EventEmitter<Array<ObjectStruct>>
+          --old: EventEmitter<ObjectStruct>
+          Type annotations are not the same.
+              --new: Array<ObjectStruct>
+              --old: {a: number, b: string, c?: ?string}",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-with-optional-argument/NativeModule to native-module/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeModuleTest: Object contained a property with a type mismatch
+  -- exampleFunction: has conflicting type changes
+      --new: (a: string, b: number)=>void
+      --old: (a: string, b: number, c?: number)=>void
+      Function types have differing length of arguments
+          --new: (a: string, b: number)=>void
+          --old: (a: string, b: number, c?: number)=>void",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-with-union/NativeModule to native-module-with-union-changes/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "addedUnionCases",
+          "message": "NativeModuleTest.exampleFunction parameter 0: Union added items, but native will not expect/support them
+  -- position 4 d",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-with-union-confusing-string-literals/NativeModule to native-module-with-union/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeModuleTest: Object contained a property with a type mismatch
+  -- exampleFunction: has conflicting type changes
+      --new: (a: (a | b | c), b: number)=>void
+      --old: (a: (a | '0' | '1' | 'a long string'), b: number)=>void
+      Parameter at index 0 did not match
+          --new: (a: (a | b | c), b: number)=>void
+          --old: (a: (a | '0' | '1' | 'a long string'), b: number)=>void
+          Subtype of union at position 1 did not match
+              --new: (a | b | c)
+              --old: (a | '0' | '1' | 'a long string')
+              String literals are not equal
+                  --new: b
+                  --old: '0'",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-with-union-from-native-changes/NativeModule to native-module-with-union-from-native/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "removedUnionCases",
+          "message": "NativeModuleTest.getConstants.exampleConstant: Union removed items, but native may still provide them
+  -- position 4 d",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;
+
+exports[`codegen formattedSummarizeDiffSet reports a diff from native-module-with-union-type-changes/NativeModule to native-module-with-union/NativeModule 1`] = `
+Object {
+  "incompatibilityReport": Object {
+    "NativeModule": Object {
+      "framework": "ReactNative",
+      "incompatibleSpecs": Array [
+        Object {
+          "errorCode": "incompatibleTypes",
+          "message": "NativeModuleTest: Object contained a property with a type mismatch
+  -- exampleFunction: has conflicting type changes
+      --new: (a: (a | b | c), b: number)=>void
+      --old: (a: Union<number>, b: number)=>void
+      Parameter at index 0 did not match
+          --new: (a: (a | b | c), b: number)=>void
+          --old: (a: Union<number>, b: number)=>void
+          Type annotations are not the same.
+              --new: (a | b | c)
+              --old: Union<number>",
+        },
+      ],
+    },
+  },
+  "status": "incompatible",
+}
+`;

packages/react-native-compatibility-check/src/__tests__/utilities/getTestSchema.js

@@ -0,0 +1,27 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @format
+ * @flow strict-local
+ * @oncall react_native
+ */
+
+import type {SchemaType} from '@react-native/codegen/src/CodegenSchema';
+
+import {FlowParser} from '@react-native/codegen/src/parsers/flow/parser';
+import path from 'path';
+
+const flowParser = new FlowParser();
+
+export function getTestSchema(
+  ...filenameComponents: Array<string>
+): SchemaType {
+  const filename = path.join(...filenameComponents);
+
+  const schema = flowParser.parseFile(filename);
+
+  return schema;
+}

packages/react-native-compatibility-check/src/convertPropToBasicTypes.js

@@ -0,0 +1,104 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ * @oncall react_native
+ */
+
+import type {
+  ArrayTypeAnnotation,
+  CompleteTypeAnnotation,
+  ComponentArrayTypeAnnotation,
+  ObjectTypeAnnotation,
+  PropTypeAnnotation,
+} from '@react-native/codegen/src/CodegenSchema';
+
+export default function convertPropToBasicTypes(
+  inputType: PropTypeAnnotation | ComponentArrayTypeAnnotation['elementType'],
+): CompleteTypeAnnotation {
+  let resultingType: CompleteTypeAnnotation;
+
+  switch (inputType.type) {
+    case 'BooleanTypeAnnotation':
+      resultingType = {
+        type: 'BooleanTypeAnnotation',
+      };
+      break;
+    case 'StringTypeAnnotation':
+      resultingType = {
+        type: 'StringTypeAnnotation',
+      };
+      break;
+    case 'DoubleTypeAnnotation':
+      resultingType = {
+        type: 'DoubleTypeAnnotation',
+      };
+      break;
+
+    case 'FloatTypeAnnotation':
+      resultingType = {
+        type: 'FloatTypeAnnotation',
+      };
+      break;
+    case 'Int32TypeAnnotation':
+      resultingType = {
+        type: 'Int32TypeAnnotation',
+      };
+      break;
+    case 'StringEnumTypeAnnotation':
+      resultingType = {
+        type: 'StringLiteralUnionTypeAnnotation',
+        types: inputType.options.map(option => {
+          return {
+            type: 'StringLiteralTypeAnnotation',
+            value: option,
+          };
+        }),
+      };
+      break;
+    case 'Int32EnumTypeAnnotation':
+      // Compat check doesn't yet have support for
+      // NumberLiteralUnionTypeAnnotation
+      resultingType = {
+        type: 'AnyTypeAnnotation',
+      };
+      break;
+    case 'ReservedPropTypeAnnotation':
+      resultingType = {
+        type: 'ReservedTypeAnnotation',
+        name: inputType.name,
+      };
+      break;
+    case 'MixedTypeAnnotation':
+      resultingType = inputType;
+      break;
+    case 'ObjectTypeAnnotation':
+      resultingType = ({
+        type: 'ObjectTypeAnnotation',
+        ...(inputType.baseTypes != null
+          ? {baseTypes: inputType.baseTypes}
+          : {}),
+        properties: inputType.properties.map(property => ({
+          name: property.name,
+          optional: property.optional,
+          typeAnnotation: convertPropToBasicTypes(property.typeAnnotation),
+        })),
+      }: ObjectTypeAnnotation<CompleteTypeAnnotation>);
+      break;
+    case 'ArrayTypeAnnotation':
+      resultingType = ({
+        type: 'ArrayTypeAnnotation',
+        elementType: convertPropToBasicTypes(inputType.elementType),
+      }: ArrayTypeAnnotation<CompleteTypeAnnotation>);
+      break;
+    default:
+      (inputType.type: empty);
+      throw new Error('Unexpected type ' + inputType.type);
+  }
+
+  return resultingType;
+}

packages/react-native-compatibility-check/src/index.flow.js

@@ -0,0 +1,12 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ * @oncall react_native
+ */
+
+export {compareSchemas} from './index.js';

packages/react-native-compatibility-check/src/index.js

@@ -0,0 +1,54 @@
+/**
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ *
+ * @flow strict-local
+ * @format
+ * @oncall react_native
+ */
+
+import type {
+  DiffSummary,
+  ExportableSchemaDiff,
+  FormattedDiffSummary,
+  SchemaDiff,
+} from './DiffResults';
+import type {SchemaType} from '@react-native/codegen/src/CodegenSchema';
+
+import {schemaDiffExporter} from './DiffResults.js';
+import {formatDiffSet} from './ErrorFormatting.js';
+import {buildSchemaDiff, summarizeDiffSet} from './VersionDiffing.js';
+
+class CompatCheckResult {
+  #schemaDiff: Set<SchemaDiff>;
+  #summary: ?DiffSummary;
+
+  constructor(schemaDiff: Set<SchemaDiff>) {
+    this.#schemaDiff = schemaDiff;
+  }
+
+  getSummary(): DiffSummary {
+    if (this.#summary == null) {
+      this.#summary = summarizeDiffSet(this.#schemaDiff);
+    }
+
+    return this.#summary;
+  }
+
+  getErrors(): FormattedDiffSummary {
+    return formatDiffSet(this.getSummary());
+  }
+
+  getDebugInfo(): Array<ExportableSchemaDiff> {
+    return Array.from(this.#schemaDiff, schemaDiffExporter);
+  }
+}
+
+export function compareSchemas(
+  newSchema: SchemaType,
+  oldSchema: SchemaType,
+): CompatCheckResult {
+  return new CompatCheckResult(buildSchemaDiff(newSchema, oldSchema));
+}

scripts/build/config.js

@@ -54,6 +54,10 @@ const buildConfig: BuildConfig = {
       emitTypeScriptDefs: true,
       target: 'node',
     },
+    'react-native-compatibility-check': {
+      emitTypeScriptDefs: true,
+      target: 'node',
+    },
   },
 };
 

yarn.lock

@@ -4438,6 +4438,15 @@ flow-parser@0.*:
   resolved "https://registry.yarnpkg.com/flow-parser/-/flow-parser-0.245.0.tgz#d8ad7e706d280ce6d4189a206768c32f552b5099"
   integrity sha512-xUBkkpIDfDZHAebnDEX65FCVitJUctab82KFmtP5SY4cGly1vbuYNe6Muyp0NLXrgmBChVdoC2T+3/RUHi4Mww==
 
+flow-remove-types@^2.237.2:
+  version "2.259.1"
+  resolved "https://registry.yarnpkg.com/flow-remove-types/-/flow-remove-types-2.259.1.tgz#ee78962cbd73d85f0e94183b354c43399903c734"
+  integrity sha512-H+ww7Q6c4xXFAoZGZnC37FJmA9Zzu3UpQ96q3/geCQiaZiTXmM7ZeN53DYpu4be8cvPEp15K0SZTOtaiGoWU5A==
+  dependencies:
+    hermes-parser "0.25.1"
+    pirates "^3.0.2"
+    vlq "^0.2.1"
+
 for-each@^0.3.3:
   version "0.3.3"
   resolved "https://registry.yarnpkg.com/for-each/-/for-each-0.3.3.tgz#69b447e88a0a5d32c3e7084f3f1710034b21376e"
@@ -6773,6 +6782,11 @@ node-int64@^0.4.0:
   resolved "https://registry.yarnpkg.com/node-int64/-/node-int64-0.4.0.tgz#87a9065cdb355d3182d8f94ce11188b825c68a3b"
   integrity sha512-O5lz91xSOeoXP6DulyHfllpq+Eg00MWitZIbtPfoSEvqIHdl5gfcY6hYzDWnj0qD5tz52PI08u9qUvSVeUBeHw==
 
+node-modules-regexp@^1.0.0:
+  version "1.0.0"
+  resolved "https://registry.yarnpkg.com/node-modules-regexp/-/node-modules-regexp-1.0.0.tgz#8d9dbe28964a4ac5712e9131642107c71e90ec40"
+  integrity sha512-JMaRS9L4wSRIR+6PTVEikTrq/lMGEZR43a48ETeilY0Q0iMwVnccMFrUM1k+tNzmYuIU0Vh710bCUqHX+/+ctQ==
+
 node-releases@^2.0.18:
   version "2.0.18"
   resolved "https://registry.yarnpkg.com/node-releases/-/node-releases-2.0.18.tgz#f010e8d35e2fe8d6b2944f03f70213ecedc4ca3f"
@@ -7170,6 +7184,13 @@ pinpoint@^1.1.0:
   resolved "https://registry.yarnpkg.com/pinpoint/-/pinpoint-1.1.0.tgz#0cf7757a6977f1bf7f6a32207b709e377388e874"
   integrity sha512-+04FTD9x7Cls2rihLlo57QDCcHoLBGn5Dk51SwtFBWkUWLxZaBXyNVpCw1S+atvE7GmnFjeaRZ0WLq3UYuqAdg==
 
+pirates@^3.0.2:
+  version "3.0.2"
+  resolved "https://registry.yarnpkg.com/pirates/-/pirates-3.0.2.tgz#7e6f85413fd9161ab4e12b539b06010d85954bb9"
+  integrity sha512-c5CgUJq6H2k6MJz72Ak1F5sN9n9wlSlJyEnwvpm9/y3WB4E3pHBDT2c6PEiS1vyJvq2bUxUAIu0EGf8Cx4Ic7Q==
+  dependencies:
+    node-modules-regexp "^1.0.0"
+
 pirates@^4.0.1, pirates@^4.0.4, pirates@^4.0.5, pirates@^4.0.6:
   version "4.0.6"
   resolved "https://registry.yarnpkg.com/pirates/-/pirates-4.0.6.tgz#3018ae32ecfcff6c29ba2267cbf21166ac1f36b9"
@@ -8744,6 +8765,11 @@ verror@1.10.0:
     core-util-is "1.0.2"
     extsprintf "^1.2.0"
 
+vlq@^0.2.1:
+  version "0.2.3"
+  resolved "https://registry.yarnpkg.com/vlq/-/vlq-0.2.3.tgz#8f3e4328cf63b1540c0d67e1b2778386f8975b26"
+  integrity sha512-DRibZL6DsNhIgYQ+wNdWDL2SL3bKPlVrRiBqV5yuMm++op8W4kGFtaQfCs4KEJn0wBZcHVHJ3eoywX8983k1ow==
+
 vlq@^1.0.0:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/vlq/-/vlq-1.0.1.tgz#c003f6e7c0b4c1edd623fd6ee50bbc0d6a1de468"