FbtTranslations: add support for modifying registered translations (#208

)

Summary:
This change adds a new function `getRegisteredTranslations` into `FbtTranslations` which allows us to retrieve registered translations. For convenience, it also adds a new `mergeTranslations` function that allows us to append the translations.

Use-case: I have an application with FBT and a design system with its own FBT as well. Unfortunately, registering translations overwrites any translations previously registered so the design system (or the application) cannot register their own translations without conflicting with the other part. One solution could be to get already registered translations and re-register them modified. Another solution is to merge these two translations together.

There are many other possible solutions so I am open to suggestions how to make it better.

Pull Request resolved: #208

Test Plan:
```
$ yarn jest Translations
Using Yarn from /data/users/jwatson/www/scripts/third-party/yarn/yarn
yarn run v1.9.0-20180706.1003
$ /data/users/jwatson/www/scripts/intl/js/oss-fbt/__github__/node_modules/.bin/jest Translations
 PASS   fbt-runtime  packages/fbt/lib/__tests__/FbtTranslations-test.js
  ✓ can register and get back translations (8ms)
  ✓ merges translations with the same locale as expected (3ms)
  ✓ merges translations with different locales as expected (1ms)
  ✓ merges translations with the same hash as expected (1ms)

Test Suites: 1 passed, 1 total
Tests:       4 passed, 4 total
Snapshots:   4 passed, 4 total
Time:        1.383s
Ran all test suites matching /Translations/i.
Done in 2.38s.
```

```
$ yarn 'flow:check'
Using Yarn from /data/users/jwatson/www/scripts/third-party/yarn/yarn
yarn run v1.9.0-20180706.1003
$ flow check --show-all-errors
Found 0 errors
Done in 10.50s.
```

Reviewed By: kayhadrin

Differential Revision: D27741516

Pulled By: jrwats

fbshipit-source-id: 5b89a48157965cf69611e8a004666d6c0daac359

CHANGELOG.md

@@ -51,6 +51,9 @@ List of changes for each released npm package version.
   <summary>
     Unreleased changes that have landed in master. Click to see more.
   </summary>
+
+  - [feat] Add a new `FbtTranslations.getRegisteredTranslations` function
+  - [feat] Add a new `FbtTranslations.mergeTranslations` function
 </details>
 
 - 0.16.5:

runtime/nonfb/FbtTranslations.js

@@ -14,7 +14,7 @@ import type {FbtRuntimeCallInput, FbtTranslatedInput} from 'FbtHooks';
 
 const FbtHooks = require('FbtHooks');
 
-let translatedFbts = null;
+let translatedFbts: TranslationDict = {};
 
 type TranslationStr = string;
 
@@ -30,7 +30,7 @@ const FbtTranslations = {
     const {args, options} = input;
     const hashKey = options?.hk;
     const {locale} = FbtHooks.getViewerContext();
-    const table = translatedFbts?.[locale];
+    const table = translatedFbts[locale];
     if (__DEV__) {
       if (!table && locale !== DEFAULT_SRC_LOCALE) {
         console.warn('Translations have not been provided');
@@ -49,6 +49,19 @@ const FbtTranslations = {
   registerTranslations(translations: TranslationDict): void {
     translatedFbts = translations;
   },
+
+  getRegisteredTranslations(): TranslationDict {
+    return translatedFbts;
+  },
+
+  mergeTranslations(newTranslations: TranslationDict): void {
+    Object.keys(newTranslations).forEach(locale => {
+      translatedFbts[locale] = Object.assign(
+        translatedFbts[locale] ?? {},
+        newTranslations[locale],
+      );
+    });
+  },
 };
 
 module.exports = FbtTranslations;

runtime/nonfb/__tests__/FbtTranslations-test.js

@@ -0,0 +1,68 @@
+/**
+ * (c) Facebook, Inc. and its affiliates. Confidential and proprietary.
+ *
+ * @flow
+ * @emails oncall+i18n_fbt_oss
+ */
+
+import FbtTranslations from '../FbtTranslations';
+
+describe('FbtTranslations', () => {
+  it('can register and get back translations', () => {
+    FbtTranslations.registerTranslations({en_US: {c1: 'aaa'}});
+    expect(FbtTranslations.getRegisteredTranslations()).toMatchInlineSnapshot(`
+    Object {
+      "en_US": Object {
+        "c1": "aaa",
+      },
+    }
+  `);
+  });
+
+  it('merges translations with the same locale as expected', () => {
+    FbtTranslations.registerTranslations({en_US: {c1: 'aaa'}});
+    FbtTranslations.mergeTranslations({en_US: {c2: 'bbb'}});
+    expect(FbtTranslations.getRegisteredTranslations()).toMatchInlineSnapshot(`
+    Object {
+      "en_US": Object {
+        "c1": "aaa",
+        "c2": "bbb",
+      },
+    }
+  `);
+  });
+
+  it('merges translations with different locales as expected', () => {
+    FbtTranslations.registerTranslations({en_US: {c1: 'aaa'}});
+    FbtTranslations.mergeTranslations({
+      es_MX: {c1: 'bbb'},
+      cs_CZ: {c1: 'ccc'},
+    });
+    expect(FbtTranslations.getRegisteredTranslations()).toMatchInlineSnapshot(`
+    Object {
+      "cs_CZ": Object {
+        "c1": "ccc",
+      },
+      "en_US": Object {
+        "c1": "aaa",
+      },
+      "es_MX": Object {
+        "c1": "bbb",
+      },
+    }
+  `);
+  });
+
+  it('merges translations with the same hash as expected', () => {
+    FbtTranslations.registerTranslations({en_US: {c1: 'aaa', c2: 'bbb'}});
+    FbtTranslations.mergeTranslations({en_US: {c1: 'ccc'}});
+    expect(FbtTranslations.getRegisteredTranslations()).toMatchInlineSnapshot(`
+    Object {
+      "en_US": Object {
+        "c1": "ccc",
+        "c2": "bbb",
+      },
+    }
+  `);
+  });
+});