Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/52746
The config is needed for build, so I renamed it. In this way, the formatting of js code in react-native repo will be consistently controlled by the prettier config in the root. This change will make prettier v3 upgrade easier.
Changelog: [Internal]
Reviewed By: pieterv
Differential Revision: D78700564
fbshipit-source-id: 392ed490bf814870f285c8372ff68b454e228802
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/52052
Changelog: [General][Added] - Add support for Flow opaque types in codegen for native modules
This allows us to codegen native modules that expose opaque types, but the implementation sees the type the same way they're visible in the JS spec.
Reviewed By: yungsters
Differential Revision: D76741112
fbshipit-source-id: 100ca9aa7f93d35120c52153f756436c9c380b07
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/51880
Updates the `sort-imports` lint rule.
The main change is that it enforces newlines after the last import statement.
Changelog:
[Internal]
Reviewed By: SamChou19815
Differential Revision: D76149902
fbshipit-source-id: 928871655c5de0613b18334d6fc0d71b3a971a18
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/51781
Adds `flow` to the remaining files that are lacking it in the `packages/react-native-codegen` directory.
This also adds any necessary type annotations (using comment syntax).
Changelog:
[Internal]
Reviewed By: huntie
Differential Revision: D75884727
fbshipit-source-id: 69e880b2dc63c3d6430f841652506e57436544a8
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/51524
Links in error suppressions will point to the announcement post in Flow FYI.
Changelog: [Internal]
drop-conflicts
Reviewed By: marcoww6
Differential Revision: D75188177
fbshipit-source-id: 27ea1fbee848e9371e679cf423e30bc9608edea0
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/50377
Configures the Hermes Parser to target React 19, which changes components written with Component Syntax to stop generating `forwardRef` calls (because `ref` is now a prop).
Changelog:
[General][Changed] - Configured Hermes Parser to target React 19, resulting in Component Syntax no longer producing `forwardRef` calls.
Reviewed By: javache, SamChou19815
Differential Revision: D72070021
fbshipit-source-id: b891789d4ff1cbcb8eebea3525361ab14e628b51
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/50339
Explicitly sets the default `reactRuntimeTarget` when invoking `require('hermes-parser').parse` so that it'll be easier to find these configurations when upgrading to `'19'`.
Changelog:
[Internal]
Reviewed By: javache
Differential Revision: D72006705
fbshipit-source-id: 4994917152a2a4a767b871d4a36092c0c5391324
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/49950
Changelog: [GENERAL][CHANGED] - Changed `react-native-codegen` to support types under `CodegenTypes` namespace
## Summary
Currently, codegen relies on deep importing types under `react-native/Libraries/Types/CodegenTypes` to be properly type-checked. Updating codegen to support types under a single namespace will enable us to provide a single import from the package with access to all relevant types.
Reviewed By: huntie
Differential Revision: D70967809
fbshipit-source-id: 41241dcc51965f4243acd34e8b63475cb56ca67a
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/49349
Follow-up on D69454101 to add more test coverage for `$ReadOnlyArray<UnsafeMixed>` as a component prop. The new type was missing from the CodegenSchema, which revealed some gaps in tests.
Changelog: [Internal]
Reviewed By: fabriziocucci
Differential Revision: D69488035
fbshipit-source-id: 19895e55e5ec4d89a790f1c388de9eea025a316c
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/49324
Provide Android component codegen a bit more flexibility by allowing `$ReadOnlyArray<UnsafeMixed>` and avoid casting in the view manager.
Changelog: [General][Added]
Reviewed By: fabriziocucci
Differential Revision: D69454101
fbshipit-source-id: c210647deffeb01b7db8aa07266e58c42acf14ba
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/48476
Command param array types were generating invalid schemas due to untyped parser code. The invalid schemas occurred for any alias type, including custom objects and basics like Int32. This was also inconsistent between Flow and TypeScript.
We already had one component utilizing this issue, so this just codifies that support into the schema so it reflects reality. This is only a partial solution. The more full solution would be to fully encode the custom types in the schemas like we do for Native Modules.
# More Information:
Tl;dr, DebuggingOverlay is abusing a FlowFixMe in codegen commands.
## The problem:
The [CodegenSchema](https://www.internalfb.com/code/fbsource/[d3ab2f79b377]/xplat/js/react-native-github/packages/react-native-codegen/src/CodegenSchema.js?lines=220) should be the source of truth for anything that can be in the schema. If something is in the schema that isn't allowed by the types, that's a bug. We have a bug. I'm adding compat-check support for components and it's blowing up on prod schemas because DebuggingOverlay causes an invalid schema.
## The details:
Support for Arrays as arguments in commands was added to the Codegen in D51866557. [Code Pointer](https://fburl.com/code/8yy1rm0p)
The intention appears to be to support arrays of primitives. There is a TODO for supporting complex types.
```
interface NativeCommands {
+addOverlays: (
viewRef: React.ElementRef<NativeType>,
overlayColorsReadOnly: $ReadOnlyArray<string>,
)
}
```
This support was added to TypeScript in D52046165 where it types the allowed Array arguments to be only
```
{
readonly type: 'ArrayTypeAnnotation';
readonly elementType:
| Int32TypeAnnotation
| DoubleTypeAnnotation
| FloatTypeAnnotation
| BooleanTypeAnnotation
| StringTypeAnnotation
};
```
However, because the Parsers are treating the input type as `any`, it isn't safe to pass through an input value into the schema as Flow won't catch mismatches.
The Flow parser just passes it through:
```
{
type: 'ArrayTypeAnnotation',
elementType: {
// TODO: T172453752 support complex type annotation for array element
type: paramValue.typeParameters.params[0].type,
}
```
Whereas the TypeScript parser has the more correct behavior of validating the inputs and returning specific outputs. Unfortunately, the return type is also typed here as $FlowFixMe, losing most of the benefits.
```
function getPrimitiveTypeAnnotation(type: string): $FlowFixMe {
switch (type) {
case 'Int32':
return {
type: 'Int32TypeAnnotation',
};
case 'Double':
return {
type: 'DoubleTypeAnnotation',
};
case 'Float':
return {
type: 'FloatTypeAnnotation',
};
case 'TSBooleanKeyword':
return {
type: 'BooleanTypeAnnotation',
};
case 'Stringish':
case 'TSStringKeyword':
return {
type: 'StringTypeAnnotation',
};
default:
throw new Error(`Unknown primitive type "${type}"`);
}
}
```
[DebuggingOverlay](https://fburl.com/code/zfe3ipq7) is abusing this gap in the Flow parser by sticking an Array of Objects in.
```
export type ElementRectangle = {
x: number,
y: number,
width: number,
height: number,
};
...
+highlightElements: (
viewRef: React.ElementRef<DebuggingOverlayNativeComponentType>,
elements: $ReadOnlyArray<ElementRectangle>,
) => void;
...
```
This isn't allowed in the schema, but it seems to fall through the holes of the flow parser and generators.
The resulting schema from Flow is this. Note the GenericTypeAnnotation which isn't allowed to be in the schema.
```
{
"name": "highlightElements",
"optional": false,
"typeAnnotation": {
"type": "FunctionTypeAnnotation",
"params": [
{
"name": "elements",
"optional": false,
"typeAnnotation": {
"type": "ArrayTypeAnnotation",
"elementType": {
"type": "GenericTypeAnnotation"
}
}
}
],
"returnTypeAnnotation": {
"type": "VoidTypeAnnotation"
}
},
```
The TypeScript parser fails with `Error: Unsupported type annotation: GenericTypeAnnotation`.
The generators don't seem to check beyond the ArrayTypeAnnotation so they fall through to generating generic arrays.
```
// ios
elements:(const NSArray *)elements
// android
ReadableArray locations
```
## So how do I fix this?
I think there are a couple of different options here. The key problem is that the Schema types need to represent reality of what can be in the schema.
1. We revert DebuggingOverlay to not use features that aren't supported (I assume nobody would be happy with this, but the change shouldn't have been made in the first place)
2. **(This is the approach taken in this diff)** We add MixedTypeAnnotation to the allowed types in Command arrays and have it generate that and add official support for that to the TypeScript parser as well. That is probably the quickest and easiest approach. It leaves the same type unsafety we have today on the native side.
3. NativeModules seem to have a lot more complex type safety here. They persist the alias type in the schema so that the CompatCheck can check them on changes. And then in C++ they generate structs and RCTConvert functions although for Java and ObjC it looks like they just use the same untyped native code. The matching approach here would be to add `aliasMap` and the whole data to the schema for commands, use that for the compat check, and still generate the same unsafe native code.
```
export type ObjectAlias = {|
x: number,
y: number,
|};
export interface Spec extends TurboModule {
+getAlias: (a: ObjectAlias) => string;
}
```
stores the ObjectAlias in the schema
```
{
"aliasMap": {
"ObjectAlias": {
"type": "ObjectTypeAnnotation",
"properties": [
{
"name": "x",
"optional": false,
"typeAnnotation": {
"type": "NumberTypeAnnotation"
}
},
{
"name": "y",
"optional": false,
"typeAnnotation": {
"type": "NumberTypeAnnotation"
}
},
]
}
},
"spec": {
"methods": [
{
"name": "getAlias",
"optional": false,
"typeAnnotation": {
"type": "FunctionTypeAnnotation",
"returnTypeAnnotation": {
"type": "StringTypeAnnotation"
},
"params": [
{
"name": "a",
"optional": false,
"typeAnnotation": {
"type": "TypeAliasTypeAnnotation",
"name": "ObjectAlias"
}
}
]
}
}
]
}
}
```
and then generates the appropriate structs on the native side and generates [this](https://www.internalfb.com/code/fbsource/[d3ab2f79b377]/xplat/js/react-native-github/packages/react-native-codegen/src/generators/modules/__tests__/__snapshots__/GenerateModuleHObjCpp-test.js.snap?lines=818)
```
Reviewed By: hoxyq
Differential Revision: D67806838
fbshipit-source-id: 31f20455c816fdb6b1a86f8f9d0f6f7d0a452754
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/48343
components store unions as 'StringEnumTypeAnnotation' even though it isn't actually a union, it's a literal.
Native Modules store these as 'StringLiteralTypeAnnotation' so this converges those and reuses the same types.
Changelog: [Internal]
Reviewed By: cipolleschi
Differential Revision: D67427656
fbshipit-source-id: e39028114285588584596012d07db40c117b4b94
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/47349
This is needed to be able to recurse into the literals and compare them.
I'm primarily unsure if there is a problem representing doubles/floats as numbers instead of strings though.
Changelog: [Internal]
Reviewed By: makovkastar
Differential Revision: D65284058
fbshipit-source-id: b2de9ed5fb7f079a432c94aaea69027863879909
Summary:
This PR adds support for negative values in enums.
Currently when we try to use an enum with negative value:
```ts
enum MyEnum {
ZERO = 0,
POSITIVE = 1,
NEGATIVE = -1,
}
export interface Spec extends TurboModule {
useArg(arg: MyEnum): void;
}
export default TurboModuleRegistry.get<Spec>('Foo');
```
It will fail:
```
Enum values can not be mixed. They all must be either blank, number, or string values.
```
This is because negative values are parsed as `UnaryExpressions` which have `-` operator in front and value as argument.
With the new approach codegen properly generates enums with negative values.
## Changelog:
[GENERAL] [ADDED] - Codegen: Support negative values in enums
Pull Request resolved: https://github.com/facebook/react-native/pull/47452
Test Plan: I've added tests to see if everything is working properly
Reviewed By: vzaidman
Differential Revision: D65887888
Pulled By: elicwhite
fbshipit-source-id: edb25f663dc58afa68c69cb84a47cfc67fc1f7e7
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/47324
I need to reference this type somewhere else, but not an array of the type.
Generally we prefer that all exported types are the object itself, and it used as a member type of arrays when used.
Changelog: [Internal]
Reviewed By: makovkastar
Differential Revision: D65259014
fbshipit-source-id: 35fb5fe03a44bed61ad87337d0fc5c198744c0e9
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/47323
This change adds support for number literals as a type.
The codegen already has parsing support for these types
```
+passNumber: (arg: number) => void;
+passString: (arg: string) => void;
+passStringLiteral: (arg: 'A String Literal') => void;
```
This change now also supports
```
+passNumberLiteral: (arg: 4) => void;
```
On the native side this is treated the same as `number`. It could be strengthened in the future.
This is a pre-requisite for number literal unions and enums.
Changelog: [Added] Codegen: Added support for Number literals in native module specs
Reviewed By: makovkastar
Differential Revision: D65249334
fbshipit-source-id: 98b051d2a6bd1ad5cc6473ac88acfcbe82bd5c7d
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/47229
Adding a test case for an enum value in a fromNative position
Changelog: [Internal]
Reviewed By: makovkastar
Differential Revision: D65038107
fbshipit-source-id: ed323d9a8b226be3ff571c86fda617cabc17cdb9
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/47109
Fixes the `lint/sort-imports` errors that are now surfaced after fixing the lint configuration.
For a couple files, I added lint suppressions instead because the unsorted import ordering is important due to interleaved calls with side effects.
Changelog:
[Internal]
Reviewed By: GijsWeterings
Differential Revision: D64569485
fbshipit-source-id: 26415d792e2b9efe08c05d1436f723faae549882
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/46845
Previously, the parser was throwing away the values of a string union when storing it in the schema. It would only store the union as
```
{
type: 'UnionTypeAnnotation',
memberType: 'StringTypeAnnotation'
}
```
We now track the string literals through the parser and store them in the schema:
```
{
type: 'StringLiteralUnionTypeAnnotation',
types: [
{
type: 'StringLiteralTypeAnnotation'
value: 'light'
},
{
type: 'StringLiteralTypeAnnotation'
value: 'dark'
},
],
}
```
We aren't changing the generators, those still just output "string". They could eventually be made smarter.
The value of this is that the compat checker can now error when the union changes.
Changelog: [Internal]
Reviewed By: yungsters
Differential Revision: D63917685
fbshipit-source-id: 34a10e1f1910d2935837a3659f66049fd4473134
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/46827
You can now define a native module that takes an argument that is a specific string literal:
Like this:
```
export interface Spec extends TurboModule {
+passString: (arg: string) => void;
+passStringLiteral: (arg: 'A String Literal') => void;
}
```
On the native side, this will still generate `string`, but the schema will now store the string literal, and it will be allowed in JS. This should allow more strict flow / typescript types for modules.
This will also allow the compatibility check to fail if the literal changes.
This is a step towards accepting a union of string literals.
Changelog: [General][Added] Codegen for Native Modules now supports string literals
Reviewed By: GijsWeterings
Differential Revision: D63872440
fbshipit-source-id: e54b97d34af4a3d1af51727db0777f26fb7b778c
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/46747
You can now use unions in native modules.
Support for this pretty much existed, but one callsite was throwing for non-cpp modules which meant nobody could use this.
Previously, StructCollector would throw that this was not supported because it couldn't generate it for objc. Instead of generating something smart in the native code for each option, it just tells native to treat them like the base type (number, string, object).
Changelog: [General][Added] Codegen now supports Union Types in NativeModules
Reviewed By: GijsWeterings
Differential Revision: D63664505
fbshipit-source-id: 73278ed9cd64452173c5170aba44ced71181510f
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/46727
It makes scripts operating on the schema complicated when the elementType might be there or might not. Let's make it required, but VoidTypeAnnotation if it's unknown.
Arguably we shouldn't allow it to be unknown at all, but that's out of scope here.
Changelog: [Internal]
Reviewed By: GijsWeterings
Differential Revision: D63616703
fbshipit-source-id: 290586384b911928e55344aa522bd296f23a074c
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/46726
An object isn't allowed to have both an indexer and regular properties. Previously, the schema just wouldn't include the properties and would only include the indexer. Instead of failing silently and not generating the expected code, let's explicitly error out.
Changelog: [Internal]
Reviewed By: GijsWeterings
Differential Revision: D63615090
fbshipit-source-id: a4c881b7a809f0b467509f7f7e2131be59ee274e
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/46488
React.Ref includes string | number to support legacy string ref, which will be killed in React 19. Therefore, the type is deprecated in Flow. This diff changes the type to use React.RefSetter instead.
Changelog: [Internal]
Reviewed By: NickGerleman
Differential Revision: D62649800
fbshipit-source-id: 81bcfbb052e2039b23829dac8de242bfb0fdca3a
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/46221
Previously the schema special cased unparseable elementType with elementType just being undefined. This causes issues for logic that requires recursively matching types. Instead of being implicit, this makes them explicitly an AnyTypeAnnotation
Changelog: [Internal]
Reviewed By: makovkastar
Differential Revision: D61825742
fbshipit-source-id: 47bf70d32d21647896d8f5319087378cc8ac8d4f
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/46220
We'll want to eventually combine the module and component capabilities more, but these are at least the trivially shared ones.
More work is required to merge the more complex object types.
This change also makes it more clear where capabilities are different between native modules and components
Changelog: [Internal]
Reviewed By: makovkastar
Differential Revision: D61740140
fbshipit-source-id: 9e7bf740cf6cd2431be8cad822ec69903dbbc71f
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/44906
Shows a proof of concept how '*strongly typed Turbo Module scoped*' `EventEmitters` can be used in a Java Turbo Module.
## Changelog:
[Android] [Added] - Add Java Turbo Module Event Emitter example
Reviewed By: javache
Differential Revision: D57530807
fbshipit-source-id: 04261d8885760f0e3b3c8c1931e0d56a5d33a0df
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/44919
## Changelog:
[Internal] [Fixed] - Call Turbo Module methods 'methods' in the Turbo Module JSON schema
We don't support `properties` on Turbo Modules. We only support methods (even eventEmitters are just methods)
Reviewed By: javache
Differential Revision: D58510557
fbshipit-source-id: 02b1dc93a37b58b47bb9fd94a9658b5a7301bf55
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/44809
Adding react-native-codegen parser support for a new `EventEmitter` property type on C++ Turbo Modules.
It is possible to later expand this feature to other languages (Java, ObjC).
## Characteristics
An `EventEmitter` must:
- be non null:
`EventEmitter<string>` works, `?EventEmitter<string>` does NOT
- have a non null eventType:
`EventEmitter<number>` works, `EventEmitter<?number>` does NOT
- have at most 1 eventType, `void` is possible as well:
`EventEmitter<>` or `EventEmitter<MyObject>` work - `EventEmitter<number, string>` do NOT
- have a concrete eventType, `{}` is not allowed
`EventEmitter<{}>` does NOT work
- be used in `Cxx` Turbo Modules only at this time
## Example
For these 4 eventEmitters in on an RN JS TM spec
```
+onPress: EventEmitter<void>;
+onClick: EventEmitter<string>;
+onChange: EventEmitter<ObjectStruct>;
+onSubmit: EventEmitter<ObjectStruct[]>;
```
We now generate this code:
1.) in the spec based header `{MyModuleName}CxxSpec` in the constructor:
```
... // existing code
eventEmitterMap_["onPress"] = std::make_shared<AsyncEventEmitter<>>();
eventEmitterMap_["onClick"] = std::make_shared<AsyncEventEmitter<OnClickType>>();
eventEmitterMap_["onChange"] = std::make_shared<AsyncEventEmitter<OnChangeType>>();
eventEmitterMap_["onSubmit"] = std::make_shared<AsyncEventEmitter<OnSubmitType>>();
```
2.) as `protected` functions
```
void emitOnPress() {
std::static_pointer_cast<AsyncEventEmitter<>>(delegate_.eventEmitterMap_["onPress"])->emit();
}
void emitOnClick(const OnClickType& value) {
std::static_pointer_cast<AsyncEventEmitter<OnClickType>>(delegate_.eventEmitterMap_["onClick"])->emit(value);
}
void emitOnChange(const OnChangeType& value) {
std::static_pointer_cast<AsyncEventEmitter<OnChangeType>>(delegate_.eventEmitterMap_["onChange"])->emit(value);
}
void emitOnSubmit(const OnSubmitType& value) {
std::static_pointer_cast<AsyncEventEmitter<OnSubmitType>>(delegate_.eventEmitterMap_["onSubmit"])->emit(value);
}
```
## Changelog:
[General] [Added] - Add EventEmitter code-gen support for C++ Turbo Modules
Reviewed By: javache
Differential Revision: D57407871
fbshipit-source-id: 2345cc6dacf0cb0d45f8a374ad9d4cbf8082f9d6
Summary:
The motiviation of this change is to produce sorted / stable native module schemas which members are alphabetically sorted. The benefit is mainly for verifying test fixtures as now new test cases will be inserted at predicatable spots.
Changelog: [Internal]
Reviewed By: rshest
Differential Revision: D56741776
fbshipit-source-id: 842af73cac3b4859d2074e6a5206015924e87201
Summary:
Changelog: [General][BREAKING] Don't support 'float' enums in Turbo Modules
- The current implementation of 'float enums' in C++ does not work as invalid results are returned.
- At potential fix could still cause rounding errors when crossing language bounaries, e.g. `4.6` can become `4.5599999942..`
- C++ enum classes don't support float: https://eel.is/c++draft/dcl.enum#2.sentence-4
> The type-specifier-seq of an enum-base shall name an integral type; any cv-qualification is ignored.
Hence removing the feature of `float enums` for now
Reviewed By: NickGerleman
Differential Revision: D52120405
fbshipit-source-id: 3685ad0629e16ff9db424ba67e07d09df6027553
Summary:
This enables to code-gen base C++ types for custom exported JS types from a RN TM spec - which have been previously excluded from code-gen as these aren't used in any function.
The only work around so far was to ‘register’ a random function using the custom type which should be used for RCTDeviceEventEmitter events
Changelog: [Internal]
Reviewed By: rshest
Differential Revision: D56685903
fbshipit-source-id: add9ca40018b91c9fca98609ba3d1f85d3affec1
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/42360
In cases where you merge out-of-tree platforms like react-native-windows with react-native mobile JS files, codegen awareness of the Windows suffix is useful. This helps prevent the creation of generated code for iOS and Android in mixed out-of-tree platform folders.
## Changelog
[Internal]
Reviewed By: mdvacca
Differential Revision: D52873212
fbshipit-source-id: ad6b1471e63d68057f54c79141123fb15f8aab5e
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/41866
Direct recursive member types require infinite memory and aren't possible with current hardware.
Throw parser error to make this visible.
Changelog: [Internal]
Reviewed By: rshest
Differential Revision: D51999832
fbshipit-source-id: 671f87325f33dd24f70ff3e2229c9d0b888d7445
Summary:
Pull Request resolved: https://github.com/facebook/react-native/pull/41767
Changelog: [Internal]
Adds a simple example showing a direct recursive node in a Cxx TM.
Currently we can't auto-generate [the necessary C++ Types](https://reactnative.dev/docs/next/the-new-architecture/cxx-custom-types#struct-generator) - but we can add it later if this scenarios becomes really common.
Direct recursive nodes, can't be value types - it would require infinite memory. Hence they are nullable and managed by a smart pointer.
Reviewed By: rshest
Differential Revision: D51784136
fbshipit-source-id: f6f0710d03583bdf1e6e72ba42d8df7f8ff8d915
Marco Wang
Sam Zhou
Rubén Norte
Tim Yung
Panos Vekris
Jakub Piasecki
Pieter De Baets
Eli White
Oskar Kwaśniewski
Christoph Purrer
Gijs Weterings
Eric Rozell
Zeya Peng