extract emitMixedTypeAnnotation to parsers-commons (#34954)

Summary:
Create a function emitMixedTypeAnnotation into the parsers-commons.js file to put together this code from [Flow](https://github.com/facebook/react-native/blob/main/packages/react-native-codegen/src/parsers/flow/modules/index.js#L400-L404) and [TypeScript](https://github.com/facebook/react-native/blob/main/packages/react-native-codegen/src/parsers/typescript/modules/index.js#L435-L440).

Part of https://github.com/facebook/react-native/issues/34872

## Changelog

<!-- Help reviewers and the release process by writing your own changelog entry. For an example, see:
https://reactnative.dev/contributing/changelogs-in-pull-requests
-->

[Internal] [Changed] - Extract emitMixedTypeAnnotation into the parsers-commons

Pull Request resolved: https://github.com/facebook/react-native/pull/34954

Test Plan:
run ```yarn jest react-native-codegen```

<img width="781" alt="image" src="https://user-images.githubusercontent.com/34857453/195291603-f138c64c-1b49-41af-a133-ee366d02706a.png">

Reviewed By: NickGerleman

Differential Revision: D40297103

Pulled By: cipolleschi

fbshipit-source-id: 3ee3569fbfa850ac50df18b74ecc3eefbeb267c9

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

@@ -14,7 +14,11 @@
 import {IncorrectlyParameterizedGenericParserError} from '../errors';
 import {assertGenericTypeAnnotationHasExactlyOneTypeParameter} from '../parsers-commons';
 
-const {wrapNullable, unwrapNullable} = require('../parsers-commons.js');
+const {
+  wrapNullable,
+  unwrapNullable,
+  emitMixedTypeAnnotation,
+} = require('../parsers-commons.js');
 
 describe('wrapNullable', () => {
   describe('when nullable is true', () => {
@@ -172,3 +176,29 @@ describe('assertGenericTypeAnnotationHasExactlyOneTypeParameter', () => {
     ).toThrow(IncorrectlyParameterizedGenericParserError);
   });
 });
+
+describe('emitMixedTypeAnnotation', () => {
+  describe('when nullable is true', () => {
+    it('returns nullable type annotation', () => {
+      const result = emitMixedTypeAnnotation(true);
+      const expected = {
+        type: 'NullableTypeAnnotation',
+        typeAnnotation: {
+          type: 'MixedTypeAnnotation',
+        },
+      };
+
+      expect(result).toEqual(expected);
+    });
+  });
+  describe('when nullable is false', () => {
+    it('returns non nullable type annotation', () => {
+      const result = emitMixedTypeAnnotation(false);
+      const expected = {
+        type: 'MixedTypeAnnotation',
+      };
+
+      expect(result).toEqual(expected);
+    });
+  });
+});

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

@@ -37,6 +37,7 @@ const {
   unwrapNullable,
   wrapNullable,
   assertGenericTypeAnnotationHasExactlyOneTypeParameter,
+  emitMixedTypeAnnotation,
 } = require('../../parsers-commons');
 const {
   emitBoolean,
@@ -414,9 +415,7 @@ function translateTypeAnnotation(
     }
     case 'MixedTypeAnnotation': {
       if (cxxOnly) {
-        return wrapNullable(nullable, {
-          type: 'MixedTypeAnnotation',
-        });
+        return emitMixedTypeAnnotation(nullable);
       }
       // Fallthrough
     }

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

@@ -15,6 +15,7 @@ import type {
   NativeModuleSchema,
   NativeModuleTypeAnnotation,
   Nullable,
+  NativeModuleMixedTypeAnnotation,
 } from '../CodegenSchema.js';
 const {IncorrectlyParameterizedGenericParserError} = require('./errors');
 import type {ParserType} from './errors';
@@ -91,9 +92,18 @@ function assertGenericTypeAnnotationHasExactlyOneTypeParameter(
   }
 }
 
+function emitMixedTypeAnnotation(
+  nullable: boolean,
+): Nullable<NativeModuleMixedTypeAnnotation> {
+  return wrapNullable(nullable, {
+    type: 'MixedTypeAnnotation',
+  });
+}
+
 module.exports = {
   wrapModuleSchema,
   unwrapNullable,
   wrapNullable,
   assertGenericTypeAnnotationHasExactlyOneTypeParameter,
+  emitMixedTypeAnnotation,
 };

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

@@ -37,6 +37,7 @@ const {
   unwrapNullable,
   wrapNullable,
   assertGenericTypeAnnotationHasExactlyOneTypeParameter,
+  emitMixedTypeAnnotation,
 } = require('../../parsers-commons');
 const {
   emitBoolean,
@@ -430,9 +431,7 @@ function translateTypeAnnotation(
     }
     case 'TSUnknownKeyword': {
       if (cxxOnly) {
-        return wrapNullable(nullable, {
-          type: 'MixedTypeAnnotation',
-        });
+        return emitMixedTypeAnnotation(nullable);
       }
       // Fallthrough
     }