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', {