Use LocaleMatcher to resolve system preferred locales

ts/scripts/gen-locales-config.ts

@@ -0,0 +1,62 @@
+// Copyright 2023 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import fs from 'fs/promises';
+import path from 'path';
+import fastGlob from 'fast-glob';
+import * as LocaleMatcher from '@formatjs/intl-localematcher';
+
+const ROOT_DIR = path.join(__dirname, '..', '..');
+
+function matches(input: string, expected: string) {
+  const match = LocaleMatcher.match([input], [expected], 'en', {
+    algorithm: 'best fit',
+  });
+  return match === expected;
+}
+
+async function main() {
+  const dirEntries = await fastGlob('_locales/*', {
+    cwd: ROOT_DIR,
+    onlyDirectories: true,
+  });
+
+  const localeDirNames = [];
+
+  for (const dirEntry of dirEntries) {
+    const dirName = path.basename(dirEntry);
+    const locale = new Intl.Locale(dirName);
+
+    // Smartling doesn't always use the correct language tag, so this check and
+    // reverse check are to make sure we don't accidentally add a locale that
+    // doesn't match its directory name (using LocaleMatcher).
+    //
+    // If this check ever fails, we may need to update our get-strings script to
+    // manually rename language tags before writing them to disk.
+    //
+    // Such is the case for Smartling's "zh-YU" locale, which we renamed to
+    // "yue" to match the language tag used by... everyone else.
+
+    if (!matches(dirName, locale.baseName)) {
+      throw new Error(
+        `Matched locale "${dirName}" does not match its resolved name "${locale.baseName}"`
+      );
+    }
+    if (!matches(locale.baseName, dirName)) {
+      throw new Error(
+        `Matched locale "${dirName}" does not match its dir name "${dirName}"`
+      );
+    }
+
+    localeDirNames.push(dirName);
+  }
+
+  const jsonPath = path.join(ROOT_DIR, 'build', 'available-locales.json');
+  console.log(`Writing to "${jsonPath}"...`);
+  await fs.writeFile(jsonPath, `${JSON.stringify(localeDirNames, null, 2)}\n`);
+}
+
+main().catch(error => {
+  console.error(error);
+  process.exit(1);
+});

ts/scripts/get-strings.ts

@@ -2,6 +2,8 @@
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import { execSync } from 'child_process';
+import fsExtra from 'fs-extra';
+import path from 'path';
 
 const { SMARTLING_USER, SMARTLING_SECRET } = process.env;
 
@@ -29,6 +31,19 @@ execSync(
   }
 );
 
+function rename(from: string, to: string) {
+  console.log(`Renaming "${from}" to "${to}"`);
+  fsExtra.moveSync(path.join('_locales', from), path.join('_locales', to), {
+    overwrite: true,
+  });
+}
+
+// Smartling uses "zh-YU" for Cantonese (or Yue Chinese).
+// This is wrong.
+// The language tag for Yue Chinese is "yue"
+// "zh-YU" actually implies "Chinese as spoken in Yugoslavia (canonicalized to Serbia)"
+rename('zh-YU', 'yue');
+
 console.log('Formatting newly-downloaded strings!');
 console.log();
 execSync('yarn format', {

ts/test-node/app/locale_test.ts

@@ -0,0 +1,46 @@
+// Copyright 2021 Signal Messenger, LLC
+// SPDX-License-Identifier: AGPL-3.0-only
+
+import { assert } from 'chai';
+import { load } from '../../../app/locale';
+import type { LoggerType } from '../../types/Logging';
+
+const logger: Pick<LoggerType, 'info' | 'warn'> = {
+  info(..._args: Array<unknown>) {
+    // noop
+  },
+  warn(..._args: Array<unknown>) {
+    throw new Error(String(_args));
+  },
+};
+
+describe('locale', async () => {
+  describe('load', () => {
+    it('resolves expected locales correctly', async () => {
+      async function testCase(
+        preferredSystemLocales: Array<string>,
+        expectedLocale: string
+      ) {
+        const actualLocale = await load({ preferredSystemLocales, logger });
+        assert.strictEqual(actualLocale.name, expectedLocale);
+      }
+
+      // Basic tests
+      await testCase(['en'], 'en');
+      await testCase(['es'], 'es');
+      await testCase(['fr', 'hk'], 'fr');
+      await testCase(['fr-FR', 'hk'], 'fr');
+      await testCase(['fa-UK'], 'fa-IR');
+      await testCase(['an', 'fr-FR'], 'fr'); // If we ever add support for Aragonese, this test will fail.
+
+      // Specific cases we want to ensure work as expected
+      await testCase(['zh-Hant-TW'], 'zh-TW');
+      await testCase(['zh-Hant-HK'], 'zh-HK');
+      await testCase(['zh'], 'zh-CN');
+      await testCase(['yue'], 'yue');
+      await testCase(['ug'], 'ug');
+      await testCase(['nn', 'nb'], 'nb');
+      await testCase(['es-419'], 'es');
+    });
+  });
+});

ts/test-node/app/menu_test.ts

@@ -202,9 +202,6 @@ describe('createTemplate', () => {
       info(_arg: unknown) {
         // noop
       },
-      error(arg: unknown) {
-        throw new Error(String(arg));
-      },
       warn(arg: unknown) {
         throw new Error(String(arg));
       },