feat: Support overriding native endorsed plugins (#137040)

These changes allow to override existing native endorsed (federated & inline) plugins with e.g. non-endorsed plugin implementations via direct dependencies as described in the section *Platform implementation selection* in the [design doc](https://docs.google.com/document/d/1LD7QjmzJZLCopUrFAAE98wOUQpjmguyGTN2wd_89Srs).

```yaml
# pubspec.yaml
name: example
dependencies:
  my_plugin: ^0.0.1
  my_plugin_android_alternative: ^0.0.1
```

Closes #80374, closes #59657

Related: Override Dart plugins (#87991, #79669)

packages/flutter_tools/lib/src/flutter_plugins.dart

@@ -106,6 +106,12 @@ Future<List<Plugin>> findPlugins(FlutterProject project, { bool throwOnError = t
   return plugins;
 }
 
+/// Plugin resolution type to determine the injection mechanism.
+enum _PluginResolutionType {
+  dart,
+  nativeOrDart,
+}
+
 // Key strings for the .flutter-plugins-dependencies file.
 const String _kFlutterPluginsPluginListKey = 'plugins';
 const String _kFlutterPluginsNameKey = 'name';
@@ -181,9 +187,14 @@ bool _writeFlutterPluginsList(
     project.web.pluginConfigKey,
   ];
 
+  final Map<String, List<Plugin>> resolvedPlatformPlugins = _resolvePluginImplementations(
+    plugins,
+    pluginResolutionType: _PluginResolutionType.nativeOrDart,
+  );
+
   final Map<String, Object> pluginsMap = <String, Object>{};
   for (final String platformKey in platformKeys) {
-    pluginsMap[platformKey] = _createPluginMapOfPlatform(plugins, platformKey);
+    pluginsMap[platformKey] = _createPluginMapOfPlatform(resolvedPlatformPlugins[platformKey] ?? <Plugin>[], platformKey);
   }
 
   final Map<String, Object> result = <String, Object>{};
@@ -212,18 +223,15 @@ bool _writeFlutterPluginsList(
 }
 
 /// Creates a map representation of the [plugins] for those supported by [platformKey].
+/// All given [plugins] must provide an implementation for the [platformKey].
 List<Map<String, Object>> _createPluginMapOfPlatform(
   List<Plugin> plugins,
   String platformKey,
 ) {
-  final Iterable<Plugin> resolvedPlatformPlugins = plugins.where((Plugin p) {
+  final Set<String> pluginNames = plugins.map((Plugin plugin) => plugin.name).toSet();
-    return p.platforms.containsKey(platformKey);
-  });
-
-  final Set<String> pluginNames = resolvedPlatformPlugins.map((Plugin plugin) => plugin.name).toSet();
   final List<Map<String, Object>> pluginInfo = <Map<String, Object>>[];
-  for (final Plugin plugin in resolvedPlatformPlugins) {
+  for (final Plugin plugin in plugins) {
-    // This is guaranteed to be non-null due to the `where` filter above.
+    assert(plugin.platforms[platformKey] != null, 'Plugin ${plugin.name} does not provide an implementation for $platformKey.');
     final PluginPlatform platformPlugin = plugin.platforms[platformKey]!;
     pluginInfo.add(<String, Object>{
       _kFlutterPluginsNameKey: plugin.name,
@@ -1051,10 +1059,9 @@ Future<void> injectBuildTimePluginFiles(
   bool webPlatform = false,
 }) async {
   final List<Plugin> plugins = await findPlugins(project);
-  // Sort the plugins by name to keep ordering stable in generated files.
+  final Map<String, List<Plugin>> pluginsByPlatform = _resolvePluginImplementations(plugins, pluginResolutionType: _PluginResolutionType.nativeOrDart);
-  plugins.sort((Plugin left, Plugin right) => left.name.compareTo(right.name));
   if (webPlatform) {
-    await _writeWebPluginRegistrant(project, plugins, destination);
+    await _writeWebPluginRegistrant(project, pluginsByPlatform[WebPlugin.kConfigKey]!, destination);
   }
 }
 
@@ -1081,22 +1088,22 @@ Future<void> injectPlugins(
   DarwinDependencyManagement? darwinDependencyManagement,
 }) async {
   final List<Plugin> plugins = await findPlugins(project);
-  // Sort the plugins by name to keep ordering stable in generated files.
+  final Map<String, List<Plugin>> pluginsByPlatform = _resolvePluginImplementations(plugins, pluginResolutionType: _PluginResolutionType.nativeOrDart);
-  plugins.sort((Plugin left, Plugin right) => left.name.compareTo(right.name));
+
   if (androidPlatform) {
-    await _writeAndroidPluginRegistrant(project, plugins);
+    await _writeAndroidPluginRegistrant(project, pluginsByPlatform[AndroidPlugin.kConfigKey]!);
   }
   if (iosPlatform) {
-    await _writeIOSPluginRegistrant(project, plugins);
+    await _writeIOSPluginRegistrant(project, pluginsByPlatform[IOSPlugin.kConfigKey]!);
   }
   if (linuxPlatform) {
-    await _writeLinuxPluginFiles(project, plugins);
+    await _writeLinuxPluginFiles(project, pluginsByPlatform[LinuxPlugin.kConfigKey]!);
   }
   if (macOSPlatform) {
-    await _writeMacOSPluginRegistrant(project, plugins);
+    await _writeMacOSPluginRegistrant(project, pluginsByPlatform[MacOSPlugin.kConfigKey]!);
   }
   if (windowsPlatform) {
-    await writeWindowsPluginFiles(project, plugins, globals.templateRenderer, allowedPlugins: allowedPlugins);
+    await writeWindowsPluginFiles(project, pluginsByPlatform[WindowsPlugin.kConfigKey]!, globals.templateRenderer, allowedPlugins: allowedPlugins);
   }
   if (iosPlatform || macOSPlatform) {
     final DarwinDependencyManagement darwinDependencyManagerSetup = darwinDependencyManagement ?? DarwinDependencyManagement(
@@ -1130,7 +1137,7 @@ bool hasPlugins(FlutterProject project) {
   return _readFileContent(project.flutterPluginsFile) != null;
 }
 
-/// Resolves the platform implementation for Dart-only plugins.
+/// Resolves the plugin implementations for all platforms.
 ///
 ///   * If there is only one dependency on a package that implements the
 ///     frontend plugin for the current platform, use that.
@@ -1142,73 +1149,62 @@ bool hasPlugins(FlutterProject project) {
 ///   * Else fail.
 ///
 ///  For more details, https://flutter.dev/go/federated-plugins.
-// TODO(stuartmorgan): Expand implementation to apply to all implementations,
+///
-//  not just Dart-only, per the federated plugin spec.
+/// If [selectDartPluginsOnly] is enabled, only Dart plugin implementations are
+/// considered. Else, native and Dart plugin implementations are considered.
 List<PluginInterfaceResolution> resolvePlatformImplementation(
-  List<Plugin> plugins,
+  List<Plugin> plugins, {
-) {
+  required bool selectDartPluginsOnly,
-  const Iterable<String> platformKeys = <String>[
+}) {
-    AndroidPlugin.kConfigKey,
+  final Map<String, List<Plugin>> resolution = _resolvePluginImplementations(
-    IOSPlugin.kConfigKey,
+    plugins,
-    LinuxPlugin.kConfigKey,
+    pluginResolutionType: selectDartPluginsOnly ? _PluginResolutionType.dart : _PluginResolutionType.nativeOrDart,
-    MacOSPlugin.kConfigKey,
+  );
-    WindowsPlugin.kConfigKey,
+  return resolution.entries.expand((MapEntry<String, List<Plugin>> entry) {
-  ];
+    return entry.value.map((Plugin plugin) {
-  final List<PluginInterfaceResolution> pluginResolutions = <PluginInterfaceResolution>[];
+      return PluginInterfaceResolution(plugin: plugin, platform: entry.key);
-  bool hasResolutionError = false;
+    });
+  }).toList();
+}
+
+/// Resolves the plugin implementations for all platforms,
+/// see [resolvePlatformImplementation].
+///
+/// Only plugins which provide the according platform implementation are returned.
+Map<String, List<Plugin>> _resolvePluginImplementations(
+  List<Plugin> plugins, {
+  required _PluginResolutionType pluginResolutionType,
+}) {
+  final Map<String, List<Plugin>> pluginsByPlatform = <String, List<Plugin>>{
+    AndroidPlugin.kConfigKey: <Plugin>[],
+    IOSPlugin.kConfigKey: <Plugin>[],
+    LinuxPlugin.kConfigKey: <Plugin>[],
+    MacOSPlugin.kConfigKey: <Plugin>[],
+    WindowsPlugin.kConfigKey: <Plugin>[],
+    WebPlugin.kConfigKey: <Plugin>[],
+  };
+
   bool hasPluginPubspecError = false;
+  bool hasResolutionError = false;
 
-  for (final String platformKey in platformKeys) {
+  for (final String platformKey in pluginsByPlatform.keys) {
-    // Key: the plugin name, value: the list of plugin candidates for the implementation of [platformKey].
+    final (
-    final Map<String, List<Plugin>> pluginImplCandidates = <String, List<Plugin>>{};
+      List<Plugin> platformPluginResolutions,
-
+      bool hasPlatformPluginPubspecError,
-    // Key: the plugin name, value: the plugin name of the default implementation of [platformKey].
+      bool hasPlatformResolutionError
-    final Map<String, String> defaultImplementations = <String, String>{};
+    ) = _resolvePluginImplementationsByPlatform(
-
+      plugins,
-    for (final Plugin plugin in plugins) {
+      platformKey,
-      final String? error = _validatePlugin(plugin, platformKey);
+      pluginResolutionType: pluginResolutionType,
-      if (error != null) {
-        globals.printError(error);
-        hasPluginPubspecError = true;
-        continue;
-      }
-      final String? implementsPluginName = _getImplementedPlugin(plugin, platformKey);
-      final String? defaultImplPluginName = _getDefaultImplPlugin(plugin, platformKey);
-
-      if (defaultImplPluginName != null) {
-        // Each plugin can only have one default implementation for this [platformKey].
-        defaultImplementations[plugin.name] = defaultImplPluginName;
-      }
-      if (implementsPluginName != null) {
-        pluginImplCandidates.putIfAbsent(implementsPluginName, () => <Plugin>[]);
-        pluginImplCandidates[implementsPluginName]!.add(plugin);
-      }
-    }
-
-    final Map<String, Plugin> pluginResolution = <String, Plugin>{};
-
-    // Now resolve all the possible resolutions to a single option for each
-    // plugin, or throw if that's not possible.
-    for (final MapEntry<String, List<Plugin>> implCandidatesEntry in pluginImplCandidates.entries) {
-      final (Plugin? resolution, String? error) = _resolveImplementationOfPlugin(
-        platformKey: platformKey,
-        pluginName: implCandidatesEntry.key,
-        candidates: implCandidatesEntry.value,
-        defaultPackageName: defaultImplementations[implCandidatesEntry.key],
-      );
-      if (error != null) {
-        globals.printError(error);
-        hasResolutionError = true;
-      } else if (resolution != null) {
-        pluginResolution[implCandidatesEntry.key] = resolution;
-      }
-    }
-
-    pluginResolutions.addAll(
-      pluginResolution.values.map((Plugin plugin) {
-        return PluginInterfaceResolution(plugin: plugin, platform: platformKey);
-      }),
     );
+
+    if (hasPlatformPluginPubspecError) {
+      hasPluginPubspecError = true;
+    } else if (hasPlatformResolutionError) {
+      hasResolutionError = true;
+    } else {
+      pluginsByPlatform[platformKey] = platformPluginResolutions;
+    }
   }
   if (hasPluginPubspecError) {
     throwToolExit('Please resolve the plugin pubspec errors');
@@ -1216,14 +1212,103 @@ List<PluginInterfaceResolution> resolvePlatformImplementation(
   if (hasResolutionError) {
     throwToolExit('Please resolve the plugin implementation selection errors');
   }
-  return pluginResolutions;
+  return pluginsByPlatform;
+}
+
+/// Resolves the plugins for the given [platformKey] (Dart-only or native
+/// implementations).
+(List<Plugin> pluginImplementations, bool hasPluginPubspecError, bool hasResolutionError) _resolvePluginImplementationsByPlatform(
+  Iterable<Plugin> plugins,
+  String platformKey, {
+  _PluginResolutionType pluginResolutionType = _PluginResolutionType.nativeOrDart,
+}) {
+  bool hasPluginPubspecError = false;
+  bool hasResolutionError = false;
+
+  // Key: the plugin name, value: the list of plugin candidates for the implementation of [platformKey].
+  final Map<String, List<Plugin>> pluginImplCandidates = <String, List<Plugin>>{};
+
+  // Key: the plugin name, value: the plugin of the default implementation of [platformKey].
+  final Map<String, Plugin> defaultImplementations = <String, Plugin>{};
+
+  for (final Plugin plugin in plugins) {
+    final String? error = _validatePlugin(plugin, platformKey, pluginResolutionType: pluginResolutionType);
+    if (error != null) {
+      globals.printError(error);
+      hasPluginPubspecError = true;
+      continue;
+    }
+    final String? implementsPluginName = _getImplementedPlugin(plugin, platformKey, pluginResolutionType: pluginResolutionType);
+    final String? defaultImplPluginName = _getDefaultImplPlugin(plugin, platformKey, pluginResolutionType: pluginResolutionType);
+
+    if (defaultImplPluginName != null) {
+      final Plugin? defaultPackage = plugins.where((Plugin plugin) => plugin.name == defaultImplPluginName).firstOrNull;
+      if (defaultPackage != null) {
+        if (_hasPluginInlineImpl(defaultPackage, platformKey, pluginResolutionType: _PluginResolutionType.nativeOrDart)) {
+          if (pluginResolutionType == _PluginResolutionType.nativeOrDart ||
+              _hasPluginInlineImpl(defaultPackage, platformKey, pluginResolutionType: pluginResolutionType)) {
+            // Each plugin can only have one default implementation for this [platformKey].
+            defaultImplementations[plugin.name] = defaultPackage;
+            // No need to add the default plugin to `pluginImplCandidates`,
+            // as if the plugin is present and provides an implementation
+            // it is added via `_getImplementedPlugin`.
+          }
+        } else {
+          // Only warn, if neither an implementation for native nor for Dart is given.
+          globals.printWarning(
+            'Package ${plugin.name}:$platformKey references $defaultImplPluginName:$platformKey as the default plugin, but it does not provide an inline implementation.\n'
+            'Ask the maintainers of ${plugin.name} to either avoid referencing a default implementation via `platforms: $platformKey: default_package: $defaultImplPluginName` '
+            'or add an inline implementation to $defaultImplPluginName via `platforms: $platformKey:` `pluginClass` or `dartPluginClass`.\n',
+          );
+        }
+      } else {
+        globals.printWarning(
+          'Package ${plugin.name}:$platformKey references $defaultImplPluginName:$platformKey as the default plugin, but the package does not exist.\n'
+          'Ask the maintainers of ${plugin.name} to either avoid referencing a default implementation via `platforms: $platformKey: default_package: $defaultImplPluginName` '
+          'or create a plugin named $defaultImplPluginName.\n',
+        );
+      }
+    }
+    if (implementsPluginName != null) {
+      pluginImplCandidates.putIfAbsent(implementsPluginName, () => <Plugin>[]);
+      pluginImplCandidates[implementsPluginName]!.add(plugin);
+    }
+  }
+
+  // Key: the plugin name, value: the plugin which provides an implementation for [platformKey].
+  final Map<String, Plugin> pluginResolution = <String, Plugin>{};
+
+  // Now resolve all the possible resolutions to a single option for each
+  // plugin, or throw if that's not possible.
+  for (final MapEntry<String, List<Plugin>> implCandidatesEntry in pluginImplCandidates.entries) {
+    final (Plugin? resolution, String? error) = _resolveImplementationOfPlugin(
+      platformKey: platformKey,
+      pluginResolutionType: pluginResolutionType,
+      pluginName: implCandidatesEntry.key,
+      candidates: implCandidatesEntry.value,
+      defaultPackage: defaultImplementations[implCandidatesEntry.key],
+    );
+    if (error != null) {
+      globals.printError(error);
+      hasResolutionError = true;
+    } else if (resolution != null) {
+      pluginResolution[implCandidatesEntry.key] = resolution;
+    }
+  }
+
+  // Sort the plugins by name to keep ordering stable in generated files.
+  final List<Plugin> pluginImplementations = pluginResolution.values.toList()
+    ..sort((Plugin left, Plugin right) => left.name.compareTo(right.name));
+  return (pluginImplementations, hasPluginPubspecError, hasResolutionError);
 }
 
 /// Validates conflicting plugin parameters in pubspec, such as
 /// `dartPluginClass`, `default_package` and `implements`.
 ///
 /// Returns an error, if failing.
-String? _validatePlugin(Plugin plugin, String platformKey) {
+String? _validatePlugin(Plugin plugin, String platformKey, {
+  required _PluginResolutionType pluginResolutionType,
+}) {
   final String? implementsPackage = plugin.implementsPackage;
   final String? defaultImplPluginName = plugin.defaultPackagePlatforms[platformKey];
 
@@ -1241,10 +1326,10 @@ String? _validatePlugin(Plugin plugin, String platformKey) {
           'or avoid referencing a default implementation via `platforms: $platformKey: default_package: $defaultImplPluginName`.\n';
     }
 
-    if (_hasPluginInlineDartImpl(plugin, platformKey)) {
+    if (_hasPluginInlineImpl(plugin, platformKey, pluginResolutionType: pluginResolutionType)) {
       return 'Plugin ${plugin.name}:$platformKey which provides an inline implementation '
           'cannot also reference a default implementation for $defaultImplPluginName. '
-          'Ask the maintainers of ${plugin.name} to either remove the implementation via `platforms: $platformKey: dartPluginClass` '
+          'Ask the maintainers of ${plugin.name} to either remove the implementation via `platforms: $platformKey:${pluginResolutionType == _PluginResolutionType.dart ? ' dartPluginClass' : '` `pluginClass` or `dartPLuginClass'}` '
           'or avoid referencing a default implementation via `platforms: $platformKey: default_package: $defaultImplPluginName`.\n';
     }
   }
@@ -1262,19 +1347,22 @@ String? _validatePlugin(Plugin plugin, String platformKey) {
 ///   * The [plugin] (e.g. 'url_launcher') implements itself and then also
 ///     serves as its own default implementation.
 ///   * The [plugin] does not provide an implementation.
-String? _getImplementedPlugin(Plugin plugin, String platformKey) {
+String? _getImplementedPlugin(
-  final bool hasInlineDartImpl = _hasPluginInlineDartImpl(plugin, platformKey);
+  Plugin plugin,
+  String platformKey, {
+  _PluginResolutionType pluginResolutionType = _PluginResolutionType.nativeOrDart,
+}) {
+  if (_hasPluginInlineImpl(plugin, platformKey, pluginResolutionType: pluginResolutionType)) {
+    // Only can serve, if the plugin has an inline implementation.
 
-  if (hasInlineDartImpl) {
     final String? implementsPackage = plugin.implementsPackage;
-
-    // Only can serve, if the plugin has a dart inline implementation.
     if (implementsPackage != null && implementsPackage.isNotEmpty) {
+      // The inline plugin implements another package.
       return implementsPackage;
     }
 
-    if (_isEligibleDartSelfImpl(plugin, platformKey)) {
+    if (pluginResolutionType == _PluginResolutionType.nativeOrDart || _isEligibleDartSelfImpl(plugin, platformKey)) {
-      // The inline Dart plugin implements itself.
+      // The inline plugin implements itself.
       return plugin.name;
     }
   }
@@ -1293,16 +1381,20 @@ String? _getImplementedPlugin(Plugin plugin, String platformKey) {
 ///   * The [plugin] (e.g. 'url_launcher') implements itself and then also
 ///     serves as its own default implementation.
 ///   * The [plugin] does not reference a default implementation.
-String? _getDefaultImplPlugin(Plugin plugin, String platformKey) {
+String? _getDefaultImplPlugin(
+  Plugin plugin,
+  String platformKey, {
+  _PluginResolutionType pluginResolutionType = _PluginResolutionType.nativeOrDart,
+}) {
   final String? defaultImplPluginName =
       plugin.defaultPackagePlatforms[platformKey];
   if (defaultImplPluginName != null) {
     return defaultImplPluginName;
   }
 
-  if (_hasPluginInlineDartImpl(plugin, platformKey) &&
+  if (_hasPluginInlineImpl(plugin, platformKey, pluginResolutionType: pluginResolutionType) &&
-      _isEligibleDartSelfImpl(plugin, platformKey)) {
+      (pluginResolutionType == _PluginResolutionType.nativeOrDart || _isEligibleDartSelfImpl(plugin, platformKey))) {
-    // The inline Dart plugin serves as its own default implementation.
+    // The inline plugin serves as its own default implementation.
     return plugin.name;
   }
 
@@ -1331,7 +1423,17 @@ bool _isEligibleDartSelfImpl(Plugin plugin, String platformKey) {
   return !isDesktop || hasMinVersionForImplementsRequirement;
 }
 
-/// Determine if the plugin provides an inline dart implementation.
+/// Determine if the plugin provides an inline implementation.
+bool _hasPluginInlineImpl(
+  Plugin plugin,
+  String platformKey, {
+  required _PluginResolutionType pluginResolutionType,
+}) {
+  return pluginResolutionType == _PluginResolutionType.nativeOrDart && plugin.platforms[platformKey] != null ||
+      pluginResolutionType == _PluginResolutionType.dart && _hasPluginInlineDartImpl(plugin, platformKey);
+}
+
+/// Determine if the plugin provides an inline Dart implementation.
 bool _hasPluginInlineDartImpl(Plugin plugin, String platformKey) {
   return plugin.pluginDartClassPlatforms[platformKey] != null &&
       plugin.pluginDartClassPlatforms[platformKey] != 'none';
@@ -1343,9 +1445,10 @@ bool _hasPluginInlineDartImpl(Plugin plugin, String platformKey) {
 /// Returns an [error] string, if failing.
 (Plugin? resolution, String? error) _resolveImplementationOfPlugin({
   required String platformKey,
+  required _PluginResolutionType pluginResolutionType,
   required String pluginName,
   required List<Plugin> candidates,
-  String? defaultPackageName,
+  Plugin? defaultPackage,
 }) {
   // If there's only one candidate, use it.
   if (candidates.length == 1) {
@@ -1377,12 +1480,10 @@ bool _hasPluginInlineDartImpl(Plugin plugin, String platformKey) {
     }
   }
   // Next, defer to the default implementation if there is one.
-  if (defaultPackageName != null) {
+  if (defaultPackage != null && candidates.contains(defaultPackage)) {
-    final int defaultIndex = candidates
+    // By definition every candidate has an inline implementation
-        .indexWhere((Plugin plugin) => plugin.name == defaultPackageName);
+    assert(_hasPluginInlineImpl(defaultPackage, platformKey, pluginResolutionType: pluginResolutionType));
-    if (defaultIndex != -1) {
+    return (defaultPackage, null);
-      return (candidates[defaultIndex], null);
-    }
   }
   // Otherwise, require an explicit choice.
   if (candidates.length > 1) {
@@ -1417,6 +1518,7 @@ Future<void> generateMainDartWithPluginRegistrant(
   final List<Plugin> plugins = await findPlugins(rootProject);
   final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(
     plugins,
+    selectDartPluginsOnly: true,
   );
   final LanguageVersion entrypointVersion = determineLanguageVersion(
     mainFile,

packages/flutter_tools/lib/src/plugins.dart

@@ -142,8 +142,8 @@ class Plugin {
     }
 
     // TODO(stuartmorgan): Consider merging web into this common handling; the
-    // fact that its implementation of Dart-only plugins and default packages
+    //  fact that its implementation of Dart-only plugins and default packages
-    // are separate is legacy.
+    //  are separate is legacy.
     final List<String> sharedHandlingPlatforms = <String>[
       AndroidPlugin.kConfigKey,
       IOSPlugin.kConfigKey,
@@ -382,7 +382,7 @@ class Plugin {
   /// This is a mapping from platform config key to the default package implementation.
   final Map<String, String> defaultPackagePlatforms;
 
-  /// This is a mapping from platform config key to the plugin class for the given platform.
+  /// This is a mapping from platform config key to the Dart plugin class for the given platform.
   final Map<String, String> pluginDartClassPlatforms;
 
   /// Whether this plugin is a direct dependency of the app.

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

@@ -9,6 +9,7 @@ import 'package:file/file.dart';
 import 'package:file/memory.dart';
 import 'package:file_testing/file_testing.dart';
 import 'package:flutter_tools/src/base/error_handling_io.dart';
+import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/base/os.dart';
 import 'package:flutter_tools/src/base/platform.dart';
 import 'package:flutter_tools/src/base/time.dart';
@@ -892,11 +893,12 @@ dependencies:
         ProcessManager: () => FakeProcessManager.any(),
       });
 
-      testUsingContext("Registrant for web doesn't escape slashes in imports", () async {
+      group('Build time plugin injection', () {
-        flutterProject.isModule = true;
+        testUsingContext("Registrant for web doesn't escape slashes in imports", () async {
-        final Directory webPluginWithNestedFile =
+          flutterProject.isModule = true;
-            fs.systemTempDirectory.createTempSync('flutter_web_plugin_with_nested.');
+          final Directory webPluginWithNestedFile =
-        webPluginWithNestedFile.childFile('pubspec.yaml').writeAsStringSync('''
+          fs.systemTempDirectory.createTempSync('flutter_web_plugin_with_nested.');
+          webPluginWithNestedFile.childFile('pubspec.yaml').writeAsStringSync('''
   flutter:
     plugin:
       platforms:
@@ -904,30 +906,85 @@ dependencies:
           pluginClass: WebPlugin
           fileName: src/web_plugin.dart
   ''');
-        webPluginWithNestedFile
+          webPluginWithNestedFile
-          .childDirectory('lib')
+              .childDirectory('lib')
-          .childDirectory('src')
+              .childDirectory('src')
-          .childFile('web_plugin.dart')
+              .childFile('web_plugin.dart')
-          .createSync(recursive: true);
+              .createSync(recursive: true);
 
-        flutterProject.directory
+          flutterProject.directory
-          .childFile('.packages')
+              .childFile('.packages')
-          .writeAsStringSync('''
+              .writeAsStringSync('''
 web_plugin_with_nested:${webPluginWithNestedFile.childDirectory('lib').uri}
 ''');
 
-        final Directory destination = flutterProject.directory.childDirectory('lib');
+          final Directory destination = flutterProject.directory.childDirectory('lib');
-        await injectBuildTimePluginFiles(flutterProject, webPlatform: true, destination: destination);
+          await injectBuildTimePluginFiles(flutterProject, webPlatform: true, destination: destination);
 
-        final File registrant = flutterProject.directory
+          final File registrant = flutterProject.directory
-            .childDirectory('lib')
+              .childDirectory('lib')
-            .childFile('web_plugin_registrant.dart');
+              .childFile('web_plugin_registrant.dart');
 
-        expect(registrant.existsSync(), isTrue);
+          expect(registrant.existsSync(), isTrue);
-        expect(registrant.readAsStringSync(), contains("import 'package:web_plugin_with_nested/src/web_plugin.dart';"));
+          expect(registrant.readAsStringSync(), contains("import 'package:web_plugin_with_nested/src/web_plugin.dart';"));
-      }, overrides: <Type, Generator>{
+        }, overrides: <Type, Generator>{
-        FileSystem: () => fs,
+          FileSystem: () => fs,
-        ProcessManager: () => FakeProcessManager.any(),
+          ProcessManager: () => FakeProcessManager.any(),
+        });
+
+        testUsingContext('user-selected implementation overrides inline implementation on web', () async {
+          final List<Directory> directories = createFakePlugins(fs, <String>[
+            'user_selected_url_launcher_implementation',
+            'url_launcher',
+          ]);
+
+          // Add inline web implementation to `user_selected_url_launcher_implementation`
+          directories[0].childFile('pubspec.yaml').writeAsStringSync('''
+flutter:
+  plugin:
+    implements: url_launcher
+    platforms:
+      web:
+        pluginClass: UserSelectedUrlLauncherWeb
+        fileName: src/web_plugin.dart
+    ''');
+
+          // Add inline native implementation to `url_launcher`
+          directories[1].childFile('pubspec.yaml').writeAsStringSync('''
+flutter:
+  plugin:
+    platforms:
+      web:
+        pluginClass: InlineUrlLauncherWeb
+        fileName: src/web_plugin.dart
+    ''');
+
+          final FlutterManifest manifest = FlutterManifest.createFromString('''
+name: test
+version: 1.0.0
+
+dependencies:
+  url_launcher: ^1.0.0
+  user_selected_url_launcher_implementation: ^1.0.0
+    ''', logger: BufferLogger.test())!;
+
+          flutterProject.manifest = manifest;
+          flutterProject.isModule = true;
+
+          final Directory destination = flutterProject.directory.childDirectory('lib');
+          await injectBuildTimePluginFiles(flutterProject, webPlatform: true, destination: destination);
+
+          final File registrant = flutterProject.directory
+              .childDirectory('lib')
+              .childFile('web_plugin_registrant.dart');
+
+          expect(registrant.existsSync(), isTrue);
+          expect(registrant.readAsStringSync(), contains("import 'package:user_selected_url_launcher_implementation/src/web_plugin.dart';"));
+          expect(registrant.readAsStringSync(),  isNot(contains("import 'package:url_launcher/src/web_plugin.dart';")));
+        }, overrides: <Type, Generator>{
+          FileSystem: () => fs,
+          ProcessManager: () => FakeProcessManager.any(),
+        });
       });
 
       testUsingContext('Injecting creates generated Android registrant, but does not include Dart-only plugins', () async {
@@ -1075,6 +1132,112 @@ flutter:
         ProcessManager: () => FakeProcessManager.any(),
       });
 
+      testUsingContext('user-selected implementation overrides inline implementation', () async {
+        final List<Directory> directories = createFakePlugins(fs, <String>[
+          'user_selected_url_launcher_implementation',
+          'url_launcher',
+        ]);
+
+        // Add inline native implementation to `user_selected_url_launcher_implementation`
+        directories[0].childFile('pubspec.yaml').writeAsStringSync('''
+flutter:
+  plugin:
+    implements: url_launcher
+    platforms:
+      linux:
+        pluginClass: UserSelectedUrlLauncherLinux
+    ''');
+
+        // Add inline native implementation to `url_launcher`
+        directories[1].childFile('pubspec.yaml').writeAsStringSync('''
+flutter:
+  plugin:
+    platforms:
+      linux:
+        pluginClass: InlineUrlLauncherLinux
+    ''');
+
+        final FlutterManifest manifest = FlutterManifest.createFromString('''
+name: test
+version: 1.0.0
+
+dependencies:
+  url_launcher: ^1.0.0
+  user_selected_url_launcher_implementation: ^1.0.0
+    ''', logger: BufferLogger.test())!;
+
+        flutterProject.manifest = manifest;
+
+        await injectPlugins(flutterProject, linuxPlatform: true);
+
+        final File registrantImpl = linuxProject.managedDirectory.childFile('generated_plugin_registrant.cc');
+
+        expect(registrantImpl.existsSync(), isTrue);
+        expect(registrantImpl.readAsStringSync(), contains('user_selected_url_launcher_linux_register_with_registrar'));
+        expect(registrantImpl.readAsStringSync(), isNot(contains('inline_url_launcher_linux_register_with_registrar')));
+      }, overrides: <Type, Generator>{
+        FileSystem: () => fs,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
+      testUsingContext('user-selected implementation overrides default implementation', () async {
+        final List<Directory> directories = createFakePlugins(fs, <String>[
+          'user_selected_url_launcher_implementation',
+          'url_launcher',
+          'url_launcher_linux',
+        ]);
+
+        // Add inline native implementation to `user_selected_url_launcher_implementation`
+        directories[0].childFile('pubspec.yaml').writeAsStringSync('''
+flutter:
+  plugin:
+    implements: url_launcher
+    platforms:
+      linux:
+        pluginClass: UserSelectedUrlLauncherLinux
+    ''');
+
+        // Add default native implementation to `url_launcher`
+        directories[1].childFile('pubspec.yaml').writeAsStringSync('''
+flutter:
+  plugin:
+    platforms:
+      linux:
+        default_package: url_launcher_linux
+    ''');
+
+        // Add inline native implementation to `url_launcher_linux`
+        directories[1].childFile('pubspec.yaml').writeAsStringSync('''
+flutter:
+  plugin:
+    platforms:
+      linux:
+        pluginClass: InlineUrlLauncherLinux
+    ''');
+
+        final FlutterManifest manifest = FlutterManifest.createFromString('''
+name: test
+version: 1.0.0
+
+dependencies:
+  url_launcher: ^1.0.0
+  user_selected_url_launcher_implementation: ^1.0.0
+    ''', logger: BufferLogger.test())!;
+
+        flutterProject.manifest = manifest;
+
+        await injectPlugins(flutterProject, linuxPlatform: true);
+
+        final File registrantImpl = linuxProject.managedDirectory.childFile('generated_plugin_registrant.cc');
+
+        expect(registrantImpl.existsSync(), isTrue);
+        expect(registrantImpl.readAsStringSync(), contains('user_selected_url_launcher_linux_register_with_registrar'));
+        expect(registrantImpl.readAsStringSync(), isNot(contains('inline_url_launcher_linux_register_with_registrar')));
+      }, overrides: <Type, Generator>{
+        FileSystem: () => fs,
+        ProcessManager: () => FakeProcessManager.any(),
+      });
+
       testUsingContext('Injecting creates generated Linux registrant, but does not include Dart-only plugins', () async {
         // Create a plugin without a pluginClass.
         final Directory pluginDirectory = createFakePlugin(fs);
@@ -1662,6 +1825,7 @@ The Flutter Preview device does not support the following plugins from your pubs
         expect(plugin.pluginPodspecPath(fs, WindowsPlugin.kConfigKey), isNull);
       });
     });
+
     testWithoutContext('Symlink failures give developer mode instructions on recent versions of Windows', () async {
       final Platform platform = FakePlatform(operatingSystem: 'windows');
       final FakeOperatingSystemUtils os = FakeOperatingSystemUtils('Microsoft Windows [Version 10.0.14972.1]');