add spec for I18nManager (facebook#24908)

Summary:
Part of facebook#24875.

## Changelog

[General] [Added] - add TM spec for I18nManager
Pull Request resolved: facebook#24908

Reviewed By: fkgozali

Differential Revision: D15395163

Pulled By: RSNara

fbshipit-source-id: 8fd3a5a8ce5d0f74132efff4fae7224eab03405b

Libraries/Inspector/resolveBoxStyle.js

@@ -69,7 +69,8 @@ function resolveBoxStyle(
 
     const styleForEnd = style[prefix + 'End'];
     if (styleForEnd != null) {
-      if (I18nManager.isRTL && I18nManager.doLeftAndRightSwapInRTL) {
+      const constants = I18nManager.getConstants();
+      if (constants.isRTL && constants.doLeftAndRightSwapInRTL) {
         result.left = styleForEnd;
       } else {
         result.right = styleForEnd;
@@ -78,7 +79,8 @@ function resolveBoxStyle(
     }
     const styleForStart = style[prefix + 'Start'];
     if (styleForStart != null) {
-      if (I18nManager.isRTL && I18nManager.doLeftAndRightSwapInRTL) {
+      const constants = I18nManager.getConstants();
+      if (constants.isRTL && constants.doLeftAndRightSwapInRTL) {
         result.right = styleForStart;
       } else {
         result.left = styleForStart;

Libraries/Modal/Modal.js

@@ -271,7 +271,7 @@ class Modal extends React.Component<Props> {
   }
 }
 
-const side = I18nManager.isRTL ? 'right' : 'left';
+const side = I18nManager.getConstants().isRTL ? 'right' : 'left';
 const styles = StyleSheet.create({
   modal: {
     position: 'absolute',

Libraries/ReactNative/I18nManager.js

@@ -9,21 +9,26 @@
  */
 'use strict';
 
-type I18nManagerStatus = {
-  isRTL: boolean,
-  doLeftAndRightSwapInRTL: boolean,
-  allowRTL: (allowRTL: boolean) => {},
-  forceRTL: (forceRTL: boolean) => {},
-  swapLeftAndRightInRTL: (flipStyles: boolean) => {},
-};
+import NativeI18nManager from './NativeI18nManager';
 
-const I18nManager: I18nManagerStatus = require('../BatchedBridge/NativeModules')
-  .I18nManager || {
-  isRTL: false,
-  doLeftAndRightSwapInRTL: true,
-  allowRTL: () => {},
-  forceRTL: () => {},
-  swapLeftAndRightInRTL: () => {},
-};
+module.exports = {
+  getConstants: () => {
+    return NativeI18nManager.getConstants();
+  },
+
+  allowRTL: (shouldAllow: boolean) => {
+    NativeI18nManager.allowRTL(shouldAllow);
+  },
 
-module.exports = I18nManager;
+  forceRTL: (shouldForce: boolean) => {
+    NativeI18nManager.forceRTL(shouldForce);
+  },
+
+  swapLeftAndRightInRTL: (flipStyles: boolean) => {
+    NativeI18nManager.swapLeftAndRightInRTL(flipStyles);
+  },
+
+  isRTL: NativeI18nManager.getConstants().isRTL,
+  doLeftAndRightSwapInRTL: NativeI18nManager.getConstants()
+    .doLeftAndRightSwapInRTL,
+};

Libraries/ReactNative/NativeI18nManager.js

@@ -0,0 +1,26 @@
+/**
+ * Copyright (c) Facebook, Inc. and its 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
+ */
+
+'use strict';
+
+import type {TurboModule} from '../TurboModule/RCTExport';
+import * as TurboModuleRegistry from '../TurboModule/TurboModuleRegistry';
+
+export interface Spec extends TurboModule {
+  +getConstants: () => {|
+    isRTL: boolean,
+    doLeftAndRightSwapInRTL: boolean,
+  |};
+  allowRTL: (allowRTL: boolean) => void;
+  forceRTL: (forceRTL: boolean) => void;
+  swapLeftAndRightInRTL: (flipStyles: boolean) => void;
+}
+
+export default TurboModuleRegistry.getEnforcing<Spec>('I18nManager');

jest/setup.js

@@ -312,6 +312,15 @@ jest
       addListener: jest.fn(),
       removeListeners: jest.fn(),
     },
+    I18nManager: {
+      allowRTL: jest.fn(),
+      forceRTL: jest.fn(),
+      swapLeftAndRightInRTL: jest.fn(),
+      getConstants: () => ({
+        isRTL: false,
+        doLeftAndRightSwapInRTL: true,
+      }),
+    },
   }))
   .mock('../Libraries/ReactNative/requireNativeComponent', () => {
     const React = require('react');