[gen-l10n] Cleans up formatting of the generated file (#79517)

dev/benchmarks/test_apps/stocks/lib/i18n/stock_strings.dart

@@ -136,23 +136,21 @@ class _StockStringsDelegate extends LocalizationsDelegate<StockStrings> {
 
 StockStrings _lookupStockStrings(Locale locale) {
 
-
-// Lookup logic when language+country codes are specified.
-switch (locale.languageCode) {
-  case 'en': {
-  switch (locale.countryCode) {
-    case 'US': return StockStringsEnUs();
+  // Lookup logic when language+country codes are specified.
+  switch (locale.languageCode) {
+    case 'en': {
+      switch (locale.countryCode) {
+        case 'US': return StockStringsEnUs();
+      }
+      break;
+    }
   }
-  break;
-}
-}
 
-// Lookup logic when only language code is specified.
-switch (locale.languageCode) {
-  case 'en': return StockStringsEn();
+  // Lookup logic when only language code is specified.
+  switch (locale.languageCode) {
+    case 'en': return StockStringsEn();
     case 'es': return StockStringsEs();
-}
-
+  }
 
   throw FlutterError(
     'StockStrings.delegate failed to load unsupported locale "$locale". This is likely '

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

@@ -346,6 +346,22 @@ String generateBaseClassMethod(Message message, LocaleInfo? templateArbLocale) {
     .replaceAll('@(name)', message.resourceId);
 }
 
+// Add spaces to pad the start of each line. Skips the first line
+// assuming that the padding is already present.
+String _addSpaces(String message, {int spaces = 0}) {
+  bool isFirstLine = true;
+  return message
+    .split('\n')
+    .map((String value) {
+      if (isFirstLine) {
+        isFirstLine = false;
+        return value;
+      }
+      return value.padLeft(spaces);
+    })
+    .join('\n');
+}
+
 String _generateLookupByAllCodes(
   AppResourceBundleCollection allBundles,
   String Function(LocaleInfo) generateSwitchClauseTemplate,
@@ -365,7 +381,7 @@ String _generateLookupByAllCodes(
 
   return allCodesLookupTemplate.replaceAll(
     '@(allCodesSwitchClauses)',
-    switchClauses.join('\n    '),
+    switchClauses.join('\n        '),
   );
 }
 
@@ -383,13 +399,20 @@ String _generateLookupByScriptCode(
       return null;
     }
 
-    return nestedSwitchTemplate
+    return _addSpaces(nestedSwitchTemplate
       .replaceAll('@(languageCode)', language)
       .replaceAll('@(code)', 'scriptCode')
-      .replaceAll('@(switchClauses)', localesWithScriptCodes.map((LocaleInfo locale) {
-          return generateSwitchClauseTemplate(locale)
-            .replaceAll('@(case)', locale.scriptCode!);
-        }).join('\n        '));
+      .replaceAll('@(switchClauses)',
+        _addSpaces(
+          localesWithScriptCodes.map((LocaleInfo locale) {
+            return generateSwitchClauseTemplate(locale)
+              .replaceAll('@(case)', locale.scriptCode!);
+          }).join('\n'),
+          spaces: 8,
+        ),
+      ),
+      spaces: 4,
+    );
   }).whereType<String>();
 
   if (switchClauses.isEmpty) {
@@ -398,7 +421,7 @@ String _generateLookupByScriptCode(
 
   return languageCodeSwitchTemplate
     .replaceAll('@(comment)', '// Lookup logic when language+script codes are specified.')
-    .replaceAll('@(switchClauses)', switchClauses.join('\n    '),
+    .replaceAll('@(switchClauses)', switchClauses.join('\n      '),
   );
 }
 
@@ -416,13 +439,18 @@ String _generateLookupByCountryCode(
       return null;
     }
 
-    return nestedSwitchTemplate
-      .replaceAll('@(languageCode)', language)
-      .replaceAll('@(code)', 'countryCode')
-      .replaceAll('@(switchClauses)', localesWithCountryCodes.map((LocaleInfo locale) {
-          return generateSwitchClauseTemplate(locale)
-            .replaceAll('@(case)', locale.countryCode!);
-        }).join('\n        '));
+    return _addSpaces(
+      nestedSwitchTemplate
+        .replaceAll('@(languageCode)', language)
+        .replaceAll('@(code)', 'countryCode')
+        .replaceAll('@(switchClauses)', _addSpaces(
+          localesWithCountryCodes.map((LocaleInfo locale) {
+            return generateSwitchClauseTemplate(locale).replaceAll('@(case)', locale.countryCode!);
+          }).join('\n'),
+          spaces: 4,
+        )),
+      spaces: 4,
+    );
   }).whereType<String>();
 
   if (switchClauses.isEmpty) {
@@ -451,7 +479,7 @@ String _generateLookupByLanguageCode(
     return localesWithLanguageCode.map((LocaleInfo locale) {
       return generateSwitchClauseTemplate(locale)
         .replaceAll('@(case)', locale.languageCode);
-    }).join('\n        ');
+    }).join('\n      ');
   }).whereType<String>();
 
   if (switchClauses.isEmpty) {
@@ -1133,7 +1161,11 @@ class LocalizationsGenerator {
       .replaceAll('@(requiresFoundationImport)', useDeferredLoading ? '' : "import 'package:flutter/foundation.dart';")
       .replaceAll('@(requiresIntlImport)', _containsPluralMessage() ? "import 'package:intl/intl.dart' as intl;" : '')
       .replaceAll('@(canBeNullable)', usesNullableGetter ? '?' : '')
-      .replaceAll('@(needsNullCheck)', usesNullableGetter ? '' : '!');
+      .replaceAll('@(needsNullCheck)', usesNullableGetter ? '' : '!')
+      // Removes all trailing whitespace from the generated file.
+      .split('\n').map((String line) => line.trimRight()).join('\n')
+      // Cleans out unnecessary newlines.
+      .replaceAll('\n\n\n', '\n\n');
   }
 
   bool _containsPluralMessage() => _allMessages.any((Message message) => message.isPlural);

packages/flutter_tools/lib/src/localizations/gen_l10n_templates.dart

@@ -263,15 +263,15 @@ case '@(languageCode)': {
 }''';
 
 const String languageCodeSwitchTemplate = '''
-@(comment)
-switch (locale.languageCode) {
-  @(switchClauses)
-}
+  @(comment)
+  switch (locale.languageCode) {
+    @(switchClauses)
+  }
 ''';
 
 const String allCodesLookupTemplate = '''
-// Lookup logic when language+script+country codes are specified.
-switch (locale.toString()) {
-  @(allCodesSwitchClauses)
-}
+  // Lookup logic when language+script+country codes are specified.
+  switch (locale.toString()) {
+    @(allCodesSwitchClauses)
+  }
 ''';

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

@@ -1809,6 +1809,42 @@ import 'output-localization-file_en.dart' deferred as output-localization-file_e
       expect(localizationsFile, contains(intlImportDartCode));
     });
 
+    testUsingContext('check indentation on generated files', () {
+      _standardFlutterDirectoryL10nSetup(fs);
+
+      try {
+        LocalizationsGenerator(
+          fileSystem: fs,
+          inputPathString: defaultL10nPathString,
+          outputPathString: defaultL10nPathString,
+          templateArbFileName: defaultTemplateArbFileName,
+          outputFileString: defaultOutputFileString,
+          classNameString: defaultClassNameString,
+          useDeferredLoading: false,
+        )
+          ..loadResources()
+          ..writeOutputFiles(BufferLogger.test());
+      } on Exception catch (e) {
+        fail('Generating output files should not fail: $e');
+      }
+
+      final String localizationsFile = fs.file(
+        fs.path.join(syntheticL10nPackagePath, 'output-localization-file.dart'),
+      ).readAsStringSync();
+      // Tests a few of the lines in the generated code.
+      // Localizations lookup code
+      expect(localizationsFile.contains('  switch (locale.languageCode) {'), true);
+      expect(localizationsFile.contains("    case 'en': return AppLocalizationsEn();"), true);
+      expect(localizationsFile.contains("    case 'es': return AppLocalizationsEs();"), true);
+      expect(localizationsFile.contains('  }'), true);
+
+      // Supported locales list
+      expect(localizationsFile.contains('  static const List<Locale> supportedLocales = <Locale>['), true);
+      expect(localizationsFile.contains("    Locale('en'),"), true);
+      expect(localizationsFile.contains("    Locale('es')"), true);
+      expect(localizationsFile.contains('  ];'), true);
+    });
+
     testUsingContext('foundation package import should be omitted from file template when deferred loading = true', () {
       fs.currentDirectory.childDirectory('lib').childDirectory('l10n')..createSync(recursive: true)
         ..childFile(defaultTemplateArbFileName).writeAsStringSync(singleMessageArbFileString)