Deprecate Objective-C plugin template (#174003)

This PR marks the `--ios-language objc` flag as deprecated for plugin
creation. It introduces a warning message in the `flutter create` tool
when the flag is used, but **does not** remove the functionality at this
time. This is the first step towards its eventual removal.

## Context

As discussed in the issue, usage metrics show that Objective-C is used
in less than 4% of newly created plugins. To streamline the tool and
align with modern iOS development practices (i.e., Swift), we are
beginning the process of phasing out this option

**Changes:**
-   Adds a deprecation warning to the CLI when the `objc` flag is used.
-   Updates the `--help` text to reflect the deprecation.
- Removes obsolete tests for Objective-C plugin creation and usage
tracking.

## Testing

I have validated these changes by:

1. Manually running `flutter-dev create` with the `objc` flag to confirm
the new deprecation warning appears.
2. Verifying that creating a plugin without the --ios-language flag does
**not** trigger the warning.
3. Running the tests in the `test/commands.shard` to ensure no
regressions were introduced.
4.  CI will validate the changes to the devicelab tests.

Fixes #169683 

## Pre-launch Checklist

- [X] I read the [Contributor Guide] and followed the process outlined
there for submitting PRs.
- [X] I read the [Tree Hygiene] wiki page, which explains my
responsibilities.
- [X] I read and followed the [Flutter Style Guide], including [Features
we expect every widget to implement].
- [X] I signed the [CLA].
- [X] I listed at least one issue that this PR fixes in the description
above.
- [] I updated/added relevant documentation (doc comments with `///`).
- [] I added new tests to check the change I am making, or this PR is
[test-exempt].
- [] I followed the [breaking change policy] and added [Data Driven
Fixes] where supported.
- [X] All existing and new tests are passing.

If you need help, consider asking for advice on the #hackers-new channel
on [Discord].

**Note**: The Flutter team is currently trialing the use of [Gemini Code
Assist for
GitHub](https://developers.google.com/gemini-code-assist/docs/review-github-code).
Comments from the `gemini-code-assist` bot should not be taken as
authoritative feedback from the Flutter team. If you find its comments
useful you can update your code accordingly, but if you are unsure or
disagree with the feedback, please feel free to wait for a Flutter team
member's review for guidance on which automated comments should be
addressed.

<!-- Links -->
[Contributor Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#overview
[Tree Hygiene]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md
[test-exempt]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#tests
[Flutter Style Guide]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md
[Features we expect every widget to implement]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Style-guide-for-Flutter-repo.md#features-we-expect-every-widget-to-implement
[CLA]: https://cla.developers.google.com/
[flutter/tests]: https://github.com/flutter/tests
[breaking change policy]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Tree-hygiene.md#handling-breaking-changes
[Discord]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Chat.md
[Data Driven Fixes]:
https://github.com/flutter/flutter/blob/main/docs/contributing/Data-driven-Fixes.md

Author: okorohelijah

dev/devicelab/bin/tasks/plugin_lint_mac.dart

@@ -48,46 +48,9 @@ Future<void> main() async {
         await _tryMacOSLint(macosintegrationTestPodspec, <String>[]);
       });
 
-      section('Create Objective-C plugin');
+      section('Create plugin');
 
-      const String objcPluginName = 'test_plugin_objc';
-      await inDirectory(tempDir, () async {
-        await flutter(
-          'create',
-          options: <String>[
-            '--org',
-            'io.flutter.devicelab',
-            '--template=plugin',
-            '--platforms=ios,android',
-            '--ios-language=objc',
-            objcPluginName,
-          ],
-        );
-      });
-
-      section('Lint Objective-C iOS podspec plugin as framework');
-
-      final String objcPluginPath = path.join(tempDir.path, objcPluginName);
-      final String objcPodspecPath = path.join(objcPluginPath, 'ios', '$objcPluginName.podspec');
-      await inDirectory(tempDir, () async {
-        await exec('pod', <String>['lib', 'lint', objcPodspecPath, '--allow-warnings']);
-      });
-
-      section('Lint Objective-C iOS podspec plugin as library');
-
-      await inDirectory(tempDir, () async {
-        await exec('pod', <String>[
-          'lib',
-          'lint',
-          objcPodspecPath,
-          '--allow-warnings',
-          '--use-libraries',
-        ]);
-      });
-
-      section('Create Swift plugin');
-
-      const String swiftPluginName = 'test_plugin_swift';
+      const String pluginName = 'test_plugin';
       await inDirectory(tempDir, () async {
         await flutter(
           'create',
@@ -96,44 +59,39 @@ Future<void> main() async {
             'io.flutter.devicelab',
             '--template=plugin',
             '--platforms=ios,macos',
-            '--ios-language=swift',
-            swiftPluginName,
+            pluginName,
           ],
         );
       });
 
-      section('Lint Swift iOS podspec plugin as framework');
+      section('Lint iOS podspec plugin as framework');
 
-      final String swiftPluginPath = path.join(tempDir.path, swiftPluginName);
-      final String swiftPodspecPath = path.join(swiftPluginPath, 'ios', '$swiftPluginName.podspec');
+      final String pluginPath = path.join(tempDir.path, pluginName);
+      final String podspecPath = path.join(pluginPath, 'ios', '$pluginName.podspec');
       await inDirectory(tempDir, () async {
-        await exec('pod', <String>['lib', 'lint', swiftPodspecPath, '--allow-warnings']);
+        await exec('pod', <String>['lib', 'lint', podspecPath, '--allow-warnings']);
       });
 
-      section('Lint Swift iOS podspec plugin as library');
+      section('Lint iOS podspec plugin as library');
 
       await inDirectory(tempDir, () async {
         await exec('pod', <String>[
           'lib',
           'lint',
-          swiftPodspecPath,
+          podspecPath,
           '--allow-warnings',
           '--use-libraries',
         ]);
       });
 
-      section('Lint Swift macOS podspec plugin as framework');
+      section('Lint macOS podspec plugin as framework');
 
-      final String macOSPodspecPath = path.join(
-        swiftPluginPath,
-        'macos',
-        '$swiftPluginName.podspec',
-      );
+      final String macOSPodspecPath = path.join(pluginPath, 'macos', '$pluginName.podspec');
       await inDirectory(tempDir, () async {
         await _tryMacOSLint(macOSPodspecPath, <String>['--allow-warnings']);
       });
 
-      section('Lint Swift macOS podspec plugin as library');
+      section('Lint macOS podspec plugin as library');
 
       await inDirectory(tempDir, () async {
         await _tryMacOSLint(macOSPodspecPath, <String>['--allow-warnings', '--use-libraries']);
@@ -149,7 +107,7 @@ Future<void> main() async {
         );
       });
 
-      section('Build iOS application with Swift and Objective-C plugins as frameworks');
+      section('Build iOS application with plugins as frameworks');
 
       final String appPath = path.join(tempDir.path, iosAppName);
 
@@ -160,7 +118,7 @@ Future<void> main() async {
       // Add the new plugins we just made.
       pubspecContent = pubspecContent.replaceFirst(
         '\ndependencies:\n',
-        '\ndependencies:\n  $objcPluginName:\n    path: $objcPluginPath\n  $swiftPluginName:\n    path: $swiftPluginPath\n  url_launcher: 6.0.16\n  url_launcher_macos:\n',
+        '\ndependencies:\n  $pluginName:\n    path: $pluginPath\n  url_launcher: 6.0.16\n  url_launcher_macos:\n',
       );
       pubspec.writeAsStringSync(pubspecContent, flush: true);
 
@@ -174,7 +132,7 @@ Future<void> main() async {
         return TaskResult.failure('Expected default Podfile to contain use_frameworks');
       }
 
-      section('Build iOS application with Swift and Objective-C plugins as libraries');
+      section('Build iOS application with plugins as libraries');
 
       iosPodfileContent = iosPodfileContent.replaceAll('use_frameworks!', '');
       iosPodfile.writeAsStringSync(iosPodfileContent, flush: true);
@@ -198,26 +156,15 @@ Future<void> main() async {
 
       _validateMacOSPodfile(appPath);
 
-      section('Build macOS application with plugins as libraries');
-
-      macosPodfileContent = macosPodfileContent.replaceAll('use_frameworks!', '');
-      macOSPodfile.writeAsStringSync(macosPodfileContent, flush: true);
-
-      await inDirectory(appPath, () async {
-        await flutter('build', options: <String>['macos']);
-      });
-
-      _validateMacOSPodfile(appPath);
-
       section('Remove iOS support from plugin');
 
-      Directory(path.join(objcPluginPath, 'ios')).deleteSync(recursive: true);
+      Directory(path.join(pluginPath, 'ios')).deleteSync(recursive: true);
 
       const String iosPlatformMap = '''
       ios:
-        pluginClass: TestPluginObjcPlugin''';
+        pluginClass: TestPlugin''';
 
-      final File pluginPubspec = File(path.join(objcPluginPath, 'pubspec.yaml'));
+      final File pluginPubspec = File(path.join(pluginPath, 'pubspec.yaml'));
       String pluginPubspecContent = pluginPubspec.readAsStringSync();
       if (!pluginPubspecContent.contains(iosPlatformMap)) {
         return TaskResult.failure('Plugin pubspec.yaml missing iOS platform map');
@@ -237,10 +184,9 @@ Future<void> main() async {
       final String podfileLockOutput = podfileLockFile.readAsStringSync();
       if (!podfileLockOutput.contains(':path: ".symlinks/plugins/url_launcher_ios/ios"') ||
           !podfileLockOutput.contains(':path: Flutter')
-          // test_plugin_objc no longer supports iOS, shouldn't be present.
+          // test_plugin no longer supports iOS, shouldn't be present.
           ||
-          podfileLockOutput.contains(':path: ".symlinks/plugins/test_plugin_objc/ios"') ||
-          !podfileLockOutput.contains(':path: ".symlinks/plugins/test_plugin_swift/ios"')) {
+          podfileLockOutput.contains(':path: ".symlinks/plugins/test_plugin/ios"')) {
         print(podfileLockOutput);
         return TaskResult.failure('Podfile.lock does not contain expected pods');
       }
@@ -249,10 +195,19 @@ Future<void> main() async {
 
       checkDirectoryExists(path.join(pluginSymlinks, 'url_launcher_ios', 'ios'));
 
-      checkDirectoryExists(path.join(pluginSymlinks, 'test_plugin_swift', 'ios'));
+      // test_plugin no longer supports iOS, shouldn't exist!
+      checkDirectoryNotExists(path.join(pluginSymlinks, 'test_plugin'));
 
-      // test_plugin_objc no longer supports iOS, shouldn't exist!
-      checkDirectoryNotExists(path.join(pluginSymlinks, 'test_plugin_objc'));
+      section('Build macOS application with plugins as libraries');
+
+      macosPodfileContent = macosPodfileContent.replaceAll('use_frameworks!', '');
+      macOSPodfile.writeAsStringSync(macosPodfileContent, flush: true);
+
+      await inDirectory(appPath, () async {
+        await flutter('build', options: <String>['macos']);
+      });
+
+      _validateMacOSPodfile(appPath);
 
       return TaskResult.success(null);
     } catch (e, stackTrace) {
@@ -271,8 +226,7 @@ void _validateIosPodfile(String appPath) {
   final String podfileLockOutput = podfileLockFile.readAsStringSync();
   if (!podfileLockOutput.contains(':path: ".symlinks/plugins/url_launcher_ios/ios"') ||
       !podfileLockOutput.contains(':path: Flutter') ||
-      !podfileLockOutput.contains(':path: ".symlinks/plugins/test_plugin_objc/ios"') ||
-      !podfileLockOutput.contains(':path: ".symlinks/plugins/test_plugin_swift/ios"') ||
+      !podfileLockOutput.contains(':path: ".symlinks/plugins/test_plugin/ios"') ||
       podfileLockOutput.contains('url_launcher_macos')) {
     print(podfileLockOutput);
     throw TaskResult.failure('iOS Podfile.lock does not contain expected pods');
@@ -288,9 +242,7 @@ void _validateIosPodfile(String appPath) {
 
   checkDirectoryNotExists(path.join(pluginSymlinks, 'url_launcher_macos'));
 
-  checkDirectoryExists(path.join(pluginSymlinks, 'test_plugin_objc', 'ios'));
-
-  checkDirectoryExists(path.join(pluginSymlinks, 'test_plugin_swift', 'ios'));
+  checkDirectoryExists(path.join(pluginSymlinks, 'test_plugin', 'ios'));
 
   // Make sure no Xcode build settings are leaking derived data/build directory into the ios directory.
   checkDirectoryNotExists(path.join(appPath, 'ios', 'build'));
@@ -305,9 +257,7 @@ void _validateMacOSPodfile(String appPath) {
       !podfileLockOutput.contains(
         ':path: Flutter/ephemeral/.symlinks/plugins/url_launcher_macos/macos',
       ) ||
-      !podfileLockOutput.contains(
-        ':path: Flutter/ephemeral/.symlinks/plugins/test_plugin_swift/macos',
-      ) ||
+      !podfileLockOutput.contains(':path: Flutter/ephemeral/.symlinks/plugins/test_plugin/macos') ||
       podfileLockOutput.contains('url_launcher_ios/')) {
     print(podfileLockOutput);
     throw TaskResult.failure('macOS Podfile.lock does not contain expected pods');
@@ -328,7 +278,7 @@ void _validateMacOSPodfile(String appPath) {
 
   checkDirectoryNotExists(path.join(pluginSymlinks, 'url_launcher_ios'));
 
-  checkDirectoryExists(path.join(pluginSymlinks, 'test_plugin_swift', 'macos'));
+  checkDirectoryExists(path.join(pluginSymlinks, 'test_plugin', 'macos'));
 }
 
 Future<void> _tryMacOSLint(String podspecPath, List<String> extraArguments) async {

dev/devicelab/bin/tasks/plugin_test_ios.dart

@@ -8,12 +8,9 @@ import 'package:flutter_devicelab/tasks/plugin_tests.dart';
 Future<void> main() async {
   await task(
     combine(<TaskFunction>[
-      PluginTest('ios', <String>['-i', 'objc', '--platforms=ios']).call,
-      PluginTest('ios', <String>['-i', 'swift', '--platforms=ios']).call,
+      PluginTest('ios', <String>['--platforms=ios']).call,
       // Test that app builds with Flutter as a transitive dependency.
       PluginTest('ios', <String>[
-        '-i',
-        'objc',
         '--platforms=ios',
       ], cocoapodsTransitiveFlutterDependency: true).call,
       // Test that Dart-only plugins are supported.

dev/devicelab/lib/tasks/plugin_tests.dart

@@ -420,15 +420,6 @@ public class $pluginClass: NSObject, FlutterPlugin {
     Map<String, String>? environment,
   }) async {
     final bool isDarwin = target == 'ios' || target == 'macos';
-    if (template != 'plugin' && isDarwin) {
-      // ios-language option is only supported for plugins. Remove the -i flag and the next parameter, "swift" or
-      // "objc". This isn't proper arg parsing (for example doesn't handle -i=objc, but good enough for these tests
-      // since they blow up if -i is passed incorrectly.
-      final int indexOfIOSLanguage = options.indexOf('-i');
-      if (indexOfIOSLanguage != -1) {
-        options.removeRange(indexOfIOSLanguage, indexOfIOSLanguage + 2);
-      }
-    }
     await inDirectory(directory, () async {
       await flutter(
         'create',

packages/flutter_tools/lib/src/commands/create.dart

@@ -70,8 +70,9 @@ class CreateCommand extends FlutterCommand with CreateBase {
       defaultsTo: 'swift',
       allowed: <String>['objc', 'swift'],
       help:
-          '(deprecated) The language to use for iOS-specific code, either Swift (recommended) or Objective-C (legacy). '
-          'Only supported for "--template=plugin".',
+          '(deprecated) This option is deprecated and no longer has any effect. '
+          'Swift is always used for iOS-specific code. '
+          'This flag will be removed in a future version of Flutter.',
       hide: !verboseHelp,
     );
     argParser.addOption(
@@ -163,7 +164,6 @@ class CreateCommand extends FlutterCommand with CreateBase {
     commandHasTerminal: hasTerminal,
     createProjectType: stringArg('template'),
     createAndroidLanguage: stringArg('android-language'),
-    createIosLanguage: stringArg('ios-language'),
   );
 
   // Lazy-initialize the net utilities with values from the context.
@@ -334,21 +334,11 @@ class CreateCommand extends FlutterCommand with CreateBase {
         exitCode: 2,
       );
     } else if (argResults!.wasParsed('ios-language')) {
-      if (generateMethodChannelsPlugin) {
-        globals.printWarning(
-          'The "ios-language" option is deprecated and will be removed in a future Flutter release.',
-        );
-        if (stringArg('ios-language') == 'objc') {
-          globals.printWarning(
-            'Please comment in https://github.com/flutter/flutter/issues/169683 describing your use-case for using Objective-C instead of Swift.',
-          );
-        }
-      } else {
-        throwToolExit(
-          'The "ios-language" option is only supported for "--template=plugin".',
-          exitCode: 2,
-        );
-      }
+      globals.printWarning(
+        'The "--ios-language" option is deprecated and no longer has any effect. '
+        'Swift is always used for iOS-specific code. '
+        'This flag will be removed in a future version of Flutter.',
+      );
     }
 
     final String organization = await getOrganization();
@@ -425,7 +415,6 @@ class CreateCommand extends FlutterCommand with CreateBase {
       withFfiPackage: generateFfiPackage,
       withEmptyMain: emptyArgument,
       androidLanguage: stringArg('android-language'),
-      iosLanguage: stringArg('ios-language'),
       iosDevelopmentTeam: developmentTeam,
       ios: includeIos,
       android: includeAndroid,

packages/flutter_tools/lib/src/commands/create_base.dart

@@ -296,7 +296,6 @@ mixin CreateBase on FlutterCommand {
     String? projectDescription,
     String? androidLanguage,
     String? iosDevelopmentTeam,
-    String? iosLanguage,
     required String flutterRoot,
     required String dartSdkVersionBounds,
     String? agpVersion,
@@ -357,7 +356,6 @@ mixin CreateBase on FlutterCommand {
       'withPluginHook': withFfiPluginHook || withFfiPackage || withPlatformChannelPluginHook,
       'withEmptyMain': withEmptyMain,
       'androidLanguage': androidLanguage,
-      'iosLanguage': iosLanguage,
       'hasIosDevelopmentTeam': iosDevelopmentTeam != null && iosDevelopmentTeam.isNotEmpty,
       'iosDevelopmentTeam': iosDevelopmentTeam ?? '',
       'flutterRevision': escapeYamlString(globals.flutterVersion.frameworkRevision),

packages/flutter_tools/lib/src/reporting/custom_dimensions.dart

@@ -27,7 +27,6 @@ class CustomDimensions {
     this.commandRunProjectType,
     this.commandRunProjectHostLanguage,
     this.commandCreateAndroidLanguage,
-    this.commandCreateIosLanguage,
     this.commandRunProjectModule,
     this.commandCreateProjectType,
     this.commandPackagesNumberPlugins,
@@ -83,7 +82,6 @@ class CustomDimensions {
   final String? commandRunProjectType; // cd14
   final String? commandRunProjectHostLanguage; // cd15
   final String? commandCreateAndroidLanguage; // cd16
-  final String? commandCreateIosLanguage; // cd17
   final bool? commandRunProjectModule; // cd18
   final String? commandCreateProjectType; // cd19
   final int? commandPackagesNumberPlugins; // cd20
@@ -161,8 +159,6 @@ class CustomDimensions {
     if (commandCreateAndroidLanguage != null)
       CustomDimensionsEnum.commandCreateAndroidLanguage.cdKey: commandCreateAndroidLanguage
           .toString(),
-    if (commandCreateIosLanguage != null)
-      CustomDimensionsEnum.commandCreateIosLanguage.cdKey: commandCreateIosLanguage.toString(),
     if (commandRunProjectModule != null)
       CustomDimensionsEnum.commandRunProjectModule.cdKey: commandRunProjectModule.toString(),
     if (commandCreateProjectType != null)
@@ -276,7 +272,6 @@ class CustomDimensions {
           other.commandRunProjectHostLanguage ?? commandRunProjectHostLanguage,
       commandCreateAndroidLanguage:
           other.commandCreateAndroidLanguage ?? commandCreateAndroidLanguage,
-      commandCreateIosLanguage: other.commandCreateIosLanguage ?? commandCreateIosLanguage,
       commandRunProjectModule: other.commandRunProjectModule ?? commandRunProjectModule,
       commandCreateProjectType: other.commandCreateProjectType ?? commandCreateProjectType,
       commandPackagesNumberPlugins:
@@ -356,7 +351,6 @@ class CustomDimensions {
       map,
       CustomDimensionsEnum.commandCreateAndroidLanguage,
     ),
-    commandCreateIosLanguage: _extractString(map, CustomDimensionsEnum.commandCreateIosLanguage),
     commandRunProjectModule: _extractBool(map, CustomDimensionsEnum.commandRunProjectModule),
     commandCreateProjectType: _extractString(map, CustomDimensionsEnum.commandCreateProjectType),
     commandPackagesNumberPlugins: _extractInt(
@@ -475,7 +469,8 @@ enum CustomDimensionsEnum {
   commandRunProjectType, // cd14
   commandRunProjectHostLanguage, // cd15
   commandCreateAndroidLanguage, // cd16
-  commandCreateIosLanguage, // cd17
+  // ignore: unused_field
+  _nullCreateIosLanguageDeprecatedDoNotUse, // cd17
   commandRunProjectModule, // cd18
   commandCreateProjectType, // cd19
   commandPackagesNumberPlugins, // cd20