Revert "allow full locale in .arb files (#93401)" (#93806)

This reverts commit 16f44118.

packages/flutter_tools/lib/src/localizations/gen_l10n.dart

@@ -1151,6 +1151,7 @@ class LocalizationsGenerator {
   String _generateCode() {
     bool isBaseClassLocale(LocaleInfo locale, String language) {
       return locale.languageCode == language
+          && locale.countryCode == null
           && locale.scriptCode == null;
     }
 

packages/flutter_tools/lib/src/localizations/gen_l10n_types.dart

@@ -466,8 +466,20 @@ class AppResourceBundle {
             // If @@locale was not defined, use the filename locale suffix.
             localeString = parserLocaleString;
           } else {
-            final Locale? parseLocale = Locale.tryParse(localeString);
-            localeString = parseLocale.toString().replaceAll('-', '_');
+            // If the localeString was defined in @@locale and in the filename, verify to
+            // see if the parsed locale matches, throw an error if it does not. This
+            // prevents developers from confusing issues when both @@locale and
+            // "_{locale}" is specified in the filename.
+            if (localeString != parserLocaleString) {
+              throw L10nException(
+                'The locale specified in @@locale and the arb filename do not match. \n'
+                'Please make sure that they match, since this prevents any confusion \n'
+                'with which locale to use. Otherwise, specify the locale in either the \n'
+                'filename of the @@locale key only.\n'
+                'Current @@locale value: $localeString\n'
+                'Current filename extension: $parserLocaleString'
+              );
+            }
           }
           break;
         }
@@ -527,6 +539,22 @@ class AppResourceBundleCollection {
       }
     }
 
+    languageToLocales.forEach((String language, List<LocaleInfo> listOfCorrespondingLocales) {
+      final List<String> localeStrings = listOfCorrespondingLocales.map((LocaleInfo locale) {
+        return locale.toString();
+      }).toList();
+      if (!localeStrings.contains(language)) {
+        throw L10nException(
+          'Arb file for a fallback, $language, does not exist, even though \n'
+          'the following locale(s) exist: $listOfCorrespondingLocales. \n'
+          'When locales specify a script code or country code, a \n'
+          'base locale (without the script code or country code) should \n'
+          'exist as the fallback. Please create a {fileName}_$language.arb \n'
+          'file.'
+        );
+      }
+    });
+
     return AppResourceBundleCollection._(directory, localeToBundle, languageToLocales);
   }
 

packages/flutter_tools/test/general.shard/generate_localizations_test.dart

@@ -1014,6 +1014,51 @@ flutter:
       expect(generator.supportedLocales.contains(LocaleInfo.fromString('zh')), true);
     });
 
+    testWithoutContext('correctly requires @@locale property in arb file to match the filename locale suffix', () {
+      const String arbFileWithEnLocale = '''
+{
+  "@@locale": "en",
+  "title": "Stocks",
+  "@title": {
+    "description": "Title for the Stocks application"
+  }
+}''';
+
+      const String arbFileWithZhLocale = '''
+{
+  "@@locale": "zh",
+  "title": "标题",
+  "@title": {
+    "description": "Title for the Stocks application"
+  }
+}''';
+
+      final Directory l10nDirectory = fs.currentDirectory.childDirectory('lib').childDirectory('l10n')
+        ..createSync(recursive: true);
+      l10nDirectory.childFile('app_es.arb')
+        .writeAsStringSync(arbFileWithEnLocale);
+      l10nDirectory.childFile('app_am.arb')
+        .writeAsStringSync(arbFileWithZhLocale);
+
+      expect(
+        () {
+          LocalizationsGenerator(
+            fileSystem: fs,
+            inputPathString: defaultL10nPathString,
+            outputPathString: defaultL10nPathString,
+            templateArbFileName: 'app_es.arb',
+            outputFileString: defaultOutputFileString,
+            classNameString: defaultClassNameString,
+          ).loadResources();
+        },
+        throwsA(isA<L10nException>().having(
+          (L10nException e) => e.message,
+          'message',
+          contains('The locale specified in @@locale and the arb filename do not match.'),
+        )),
+      );
+    });
+
     testWithoutContext("throws when arb file's locale could not be determined", () {
       fs.currentDirectory.childDirectory('lib').childDirectory('l10n')
         ..createSync(recursive: true)
@@ -1072,6 +1117,30 @@ flutter:
       );
     });
 
+    testWithoutContext('throws when the base locale does not exist', () {
+      final Directory l10nDirectory = fs.currentDirectory.childDirectory('lib').childDirectory('l10n')
+        ..createSync(recursive: true);
+      l10nDirectory.childFile('app_en_US.arb')
+        .writeAsStringSync(singleMessageArbFileString);
+
+      expect(
+        () {
+          LocalizationsGenerator(
+            fileSystem: fs,
+            inputPathString: defaultL10nPathString,
+            outputPathString: defaultL10nPathString,
+            templateArbFileName: 'app_en_US.arb',
+            outputFileString: defaultOutputFileString,
+            classNameString: defaultClassNameString,
+          ).loadResources();
+        },
+        throwsA(isA<L10nException>().having(
+          (L10nException e) => e.message,
+          'message',
+          contains('Arb file for a fallback, en, does not exist'),
+        )),
+      );
+    });
   });
 
   group('writeOutputFiles', () {
@@ -1193,7 +1262,7 @@ flutter:
   /// **'The price of this item is: \${price}'**'''));
     });
 
-    testWithoutContext('should generate a file per arb', () {
+    testWithoutContext('should generate a file per language', () {
       const String singleEnCaMessageArbFileString = '''
 {
   "title": "Canadian Title"
@@ -1214,8 +1283,13 @@ flutter:
         ..writeOutputFiles(BufferLogger.test());
 
       expect(fs.isFileSync(fs.path.join(syntheticL10nPackagePath, 'output-localization-file_en.dart')), true);
-      expect(fs.isFileSync(fs.path.join(syntheticL10nPackagePath, 'output-localization-file_en_CA.dart')), true);
       expect(fs.isFileSync(fs.path.join(syntheticL10nPackagePath, 'output-localization-file_en_US.dart')), false);
+
+      final String englishLocalizationsFile = fs.file(
+        fs.path.join(syntheticL10nPackagePath, 'output-localization-file_en.dart')
+      ).readAsStringSync();
+      expect(englishLocalizationsFile, contains('class AppLocalizationsEnCa extends AppLocalizationsEn'));
+      expect(englishLocalizationsFile, contains('class AppLocalizationsEn extends AppLocalizations'));
     });
 
     testWithoutContext('language imports are sorted when preferredSupportedLocaleString is given', () {