Extract the content of the case 'StringTypeAnnotation' into a single … (#34981)

Summary:
This PR extracts the content of the codegen case 'String' into a single `emitString` function inside the parsers-primitives.js file and uses it in both Flow and TypeScript parsers as requested on https://github.com/facebook/react-native/issues/34872. This also adds unit tests to the new `emitString` function.

ref: https://github.com/facebook/react-native/pull/34936

## Changelog

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[Internal] [Changed] - Extract the content of the case 'StringTypeAnnotation' into a single emitString function

Pull Request resolved: https://github.com/facebook/react-native/pull/34981

Test Plan: Run `yarn jest react-native-codegen` and ensure CI is green

Reviewed By: cortinico

Differential Revision: D40376836

Pulled By: cipolleschi

fbshipit-source-id: feb1b07ec7fc2c333f5054f8cd8d18457d985257

packages/react-native-codegen/src/parsers/__tests__/parsers-primitives-test.js

@@ -20,6 +20,7 @@ const {
   emitPromise,
   emitRootTag,
   emitVoid,
+  emitString,
   emitStringish,
   typeAliasResolution,
 } = require('../parsers-primitives.js');
@@ -155,6 +156,33 @@ describe('emitStringish', () => {
   });
 });
 
+describe('emitString', () => {
+  describe('when nullable is true', () => {
+    it('returns nullable type annotation', () => {
+      const result = emitString(true);
+      const expected = {
+        type: 'NullableTypeAnnotation',
+        typeAnnotation: {
+          type: 'StringTypeAnnotation',
+        },
+      };
+
+      expect(result).toEqual(expected);
+    });
+  });
+
+  describe('when nullable is false', () => {
+    it('returns non nullable type annotation', () => {
+      const result = emitString(false);
+      const expected = {
+        type: 'StringTypeAnnotation',
+      };
+
+      expect(result).toEqual(expected);
+    });
+  });
+});
+
 describe('emitDouble', () => {
   describe('when nullable is true', () => {
     it('returns nullable type annotation', () => {

packages/react-native-codegen/src/parsers/flow/modules/index.js

@@ -49,6 +49,7 @@ const {
   emitPromise,
   emitRootTag,
   emitVoid,
+  emitString,
   emitStringish,
   typeAliasResolution,
 } = require('../../parsers-primitives');
@@ -354,9 +355,7 @@ function translateTypeAnnotation(
       return emitVoid(nullable);
     }
     case 'StringTypeAnnotation': {
-      return wrapNullable(nullable, {
-        type: 'StringTypeAnnotation',
-      });
+      return emitString(nullable);
     }
     case 'FunctionTypeAnnotation': {
       const translateFunctionTypeAnnotationValue: NativeModuleFunctionTypeAnnotation =

packages/react-native-codegen/src/parsers/parsers-primitives.js

@@ -86,6 +86,12 @@ function emitFunction(
   return wrapNullable(nullable, translateFunctionTypeAnnotationValue);
 }
 
+function emitString(nullable: boolean): Nullable<StringTypeAnnotation> {
+  return wrapNullable(nullable, {
+    type: 'StringTypeAnnotation',
+  });
+}
+
 function typeAliasResolution(
   typeAliasResolutionStatus: TypeAliasResolutionStatus,
   objectTypeAnnotation: ObjectTypeAnnotation<
@@ -174,7 +180,8 @@ module.exports = {
   emitObject,
   emitPromise,
   emitRootTag,
-  emitStringish,
   emitVoid,
+  emitString,
+  emitStringish,
   typeAliasResolution,
 };

packages/react-native-codegen/src/parsers/typescript/modules/index.js

@@ -49,6 +49,7 @@ const {
   emitPromise,
   emitRootTag,
   emitVoid,
+  emitString,
   emitStringish,
   typeAliasResolution,
 } = require('../../parsers-primitives');
@@ -369,9 +370,7 @@ function translateTypeAnnotation(
       return emitVoid(nullable);
     }
     case 'TSStringKeyword': {
-      return wrapNullable(nullable, {
-        type: 'StringTypeAnnotation',
-      });
+      return emitString(nullable);
     }
     case 'TSFunctionType': {
       const translateFunctionTypeAnnotationValue: NativeModuleFunctionTypeAnnotation =