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.
@@ -1142,42 +1149,125 @@ 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;
+    });
-  bool hasPluginPubspecError = 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 pluginsByPlatform.keys) {
+    final (
+      List<Plugin> platformPluginResolutions,
+      bool hasPlatformPluginPubspecError,
+      bool hasPlatformResolutionError
+    ) = _resolvePluginImplementationsByPlatform(
+      plugins,
+      platformKey,
+      pluginResolutionType: pluginResolutionType,
+    );
+
+    if (hasPlatformPluginPubspecError) {
+      hasPluginPubspecError = true;
+    } else if (hasPlatformResolutionError) {
+      hasResolutionError = true;
+    } else {
+      pluginsByPlatform[platformKey] = platformPluginResolutions;
+    }
+  }
+  if (hasPluginPubspecError) {
+    throwToolExit('Please resolve the plugin pubspec errors');
+  }
+  if (hasResolutionError) {
+    throwToolExit('Please resolve the plugin implementation selection errors');
+  }
+  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;
 
-  for (final String platformKey in platformKeys) {
   // 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 name of the default implementation of [platformKey].
+  // Key: the plugin name, value: the plugin of the default implementation of [platformKey].
-    final Map<String, String> defaultImplementations = <String, String>{};
+  final Map<String, Plugin> defaultImplementations = <String, Plugin>{};
 
   for (final Plugin plugin in plugins) {
-      final String? error = _validatePlugin(plugin, 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? implementsPluginName = _getImplementedPlugin(plugin, platformKey, pluginResolutionType: pluginResolutionType);
-      final String? defaultImplPluginName = _getDefaultImplPlugin(plugin, platformKey);
+    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] = defaultImplPluginName;
+            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>[]);
@@ -1185,6 +1275,7 @@ List<PluginInterfaceResolution> resolvePlatformImplementation(
     }
   }
 
+  // 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
@@ -1192,9 +1283,10 @@ List<PluginInterfaceResolution> resolvePlatformImplementation(
   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,
-        defaultPackageName: defaultImplementations[implCandidatesEntry.key],
+      defaultPackage: defaultImplementations[implCandidatesEntry.key],
     );
     if (error != null) {
       globals.printError(error);
@@ -1204,26 +1296,19 @@ List<PluginInterfaceResolution> resolvePlatformImplementation(
     }
   }
 
-    pluginResolutions.addAll(
+  // Sort the plugins by name to keep ordering stable in generated files.
-      pluginResolution.values.map((Plugin plugin) {
+  final List<Plugin> pluginImplementations = pluginResolution.values.toList()
-        return PluginInterfaceResolution(plugin: plugin, platform: platformKey);
+    ..sort((Plugin left, Plugin right) => left.name.compareTo(right.name));
-      }),
+  return (pluginImplementations, hasPluginPubspecError, hasResolutionError);
-    );
-  }
-  if (hasPluginPubspecError) {
-    throwToolExit('Please resolve the plugin pubspec errors');
-  }
-  if (hasResolutionError) {
-    throwToolExit('Please resolve the plugin implementation selection errors');
-  }
-  return pluginResolutions;
 }
 
 /// 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

@@ -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/dart_plugin_test.dart

@@ -43,7 +43,8 @@ void main() {
           'url_launcher_linux',
           'url_launcher_macos',
         };
-        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(<Plugin>[
+        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(
+          <Plugin>[
             Plugin.fromYaml(
               'url_launcher_linux',
               '',
@@ -76,7 +77,9 @@ void main() {
               fileSystem: fs,
               appDependencies: directDependencies,
             ),
-        ]);
+          ],
+          selectDartPluginsOnly: true,
+        );
 
         expect(resolutions.length, equals(2));
         expect(resolutions[0].toMap(), equals(
@@ -139,6 +142,7 @@ void main() {
               appDependencies: directDependencies,
             ),
           ],
+          selectDartPluginsOnly: true,
         );
 
         expect(resolutions.length, equals(1));
@@ -155,7 +159,8 @@ void main() {
         final Set<String> directDependencies = <String>{
           'url_launcher_macos',
         };
-        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(<Plugin>[
+        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(
+          <Plugin>[
             Plugin.fromYaml(
               'url_launcher_macos',
               '',
@@ -188,7 +193,9 @@ void main() {
               fileSystem: fs,
               appDependencies: directDependencies,
             ),
-        ]);
+          ],
+          selectDartPluginsOnly: true,
+        );
 
         expect(resolutions.length, equals(2));
         expect(resolutions[0].toMap(), equals(
@@ -210,7 +217,8 @@ void main() {
       testWithoutContext('selects inline implementation on mobile', () async {
         final Set<String> directDependencies = <String>{};
 
-        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(<Plugin>[
+        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(
+          <Plugin>[
             Plugin.fromYaml(
               'url_launcher',
               '',
@@ -229,7 +237,9 @@ void main() {
               fileSystem: fs,
               appDependencies: directDependencies,
             ),
-        ]);
+          ],
+          selectDartPluginsOnly: true,
+        );
         expect(resolutions.length, equals(2));
         expect(resolutions[0].toMap(), equals(
           <String, String>{
@@ -252,7 +262,8 @@ void main() {
       'missing min Flutter SDK constraint', () async {
         final Set<String> directDependencies = <String>{};
 
-        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(<Plugin>[
+        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(
+          <Plugin>[
             Plugin.fromYaml(
               'url_launcher',
               '',
@@ -274,7 +285,9 @@ void main() {
               fileSystem: fs,
               appDependencies: directDependencies,
             ),
-        ]);
+          ],
+          selectDartPluginsOnly: true,
+        );
         expect(resolutions.length, equals(0));
       });
 
@@ -283,7 +296,8 @@ void main() {
       'min Flutter SDK constraint < 2.11', () async {
         final Set<String> directDependencies = <String>{};
 
-        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(<Plugin>[
+        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(
+          <Plugin>[
             Plugin.fromYaml(
               'url_launcher',
               '',
@@ -305,7 +319,9 @@ void main() {
               fileSystem: fs,
               appDependencies: directDependencies,
             ),
-        ]);
+          ],
+          selectDartPluginsOnly: true,
+        );
         expect(resolutions.length, equals(0));
       });
 
@@ -313,7 +329,8 @@ void main() {
       'min Flutter SDK requirement of at least 2.11', () async {
         final Set<String> directDependencies = <String>{};
 
-        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(<Plugin>[
+        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(
+          <Plugin>[
             Plugin.fromYaml(
               'url_launcher',
               '',
@@ -335,7 +352,9 @@ void main() {
               fileSystem: fs,
               appDependencies: directDependencies,
             ),
-        ]);
+          ],
+          selectDartPluginsOnly: true,
+        );
         expect(resolutions.length, equals(3));
         expect(
           resolutions.map((PluginInterfaceResolution resolution) => resolution.toMap()),
@@ -362,7 +381,8 @@ void main() {
       testWithoutContext('selects default implementation', () async {
         final Set<String> directDependencies = <String>{};
 
-        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(<Plugin>[
+        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(
+          <Plugin>[
             Plugin.fromYaml(
               'url_launcher',
               '',
@@ -429,7 +449,9 @@ void main() {
               fileSystem: fs,
               appDependencies: directDependencies,
             ),
-        ]);
+          ],
+          selectDartPluginsOnly: true,
+        );
         expect(resolutions.length, equals(1));
         expect(resolutions[0].toMap(), equals(
           <String, String>{
@@ -443,7 +465,8 @@ void main() {
       testWithoutContext('selects default implementation if interface is direct dependency', () async {
         final Set<String> directDependencies = <String>{'url_launcher'};
 
-        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(<Plugin>[
+        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(
+          <Plugin>[
             Plugin.fromYaml(
               'url_launcher',
               '',
@@ -475,7 +498,9 @@ void main() {
               fileSystem: fs,
               appDependencies: directDependencies,
             ),
-        ]);
+          ],
+          selectDartPluginsOnly: true,
+        );
         expect(resolutions.length, equals(1));
         expect(resolutions[0].toMap(), equals(
           <String, String>{
@@ -486,13 +511,14 @@ void main() {
         );
       });
 
-      testWithoutContext('selects user selected implementation despite default implementation', () async {
+      testWithoutContext('user-selected implementation overrides default implementation', () async {
         final Set<String> directDependencies = <String>{
           'user_selected_url_launcher_implementation',
           'url_launcher',
         };
 
-        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(<Plugin>[
+        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(
+          <Plugin>[
             Plugin.fromYaml(
               'url_launcher',
               '',
@@ -540,7 +566,9 @@ void main() {
               fileSystem: fs,
               appDependencies: directDependencies,
             ),
-        ]);
+          ],
+          selectDartPluginsOnly: true,
+        );
         expect(resolutions.length, equals(1));
         expect(resolutions[0].toMap(), equals(
           <String, String>{
@@ -551,13 +579,14 @@ void main() {
         );
       });
 
-      testWithoutContext('selects user selected implementation despite inline implementation', () async {
+      testWithoutContext('user-selected implementation overrides inline implementation', () async {
         final Set<String> directDependencies = <String>{
           'user_selected_url_launcher_implementation',
           'url_launcher',
         };
 
-        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(<Plugin>[
+        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(
+          <Plugin>[
             Plugin.fromYaml(
               'url_launcher',
               '',
@@ -592,7 +621,9 @@ void main() {
               fileSystem: fs,
               appDependencies: directDependencies,
             ),
-        ]);
+          ],
+          selectDartPluginsOnly: true,
+        );
         expect(resolutions.length, equals(2));
         expect(resolutions[0].toMap(), equals(
             <String, String>{
@@ -617,7 +648,8 @@ void main() {
           'url_launcher',
         };
         expect(() {
-          resolvePlatformImplementation(<Plugin>[
+          resolvePlatformImplementation(
+            <Plugin>[
               Plugin.fromYaml(
                 'url_launcher',
                 '',
@@ -665,7 +697,9 @@ void main() {
                 fileSystem: fs,
                 appDependencies: directDependencies,
               ),
-          ]);
+            ],
+            selectDartPluginsOnly: true,
+          );
         },
             throwsToolExit(
               message: 'Please resolve the plugin pubspec errors',
@@ -687,7 +721,8 @@ void main() {
           'url_launcher',
         };
         expect(() {
-          resolvePlatformImplementation(<Plugin>[
+          resolvePlatformImplementation(
+            <Plugin>[
               Plugin.fromYaml(
                 'url_launcher',
                 '',
@@ -720,7 +755,9 @@ void main() {
                 fileSystem: fs,
                 appDependencies: directDependencies,
               ),
-          ]);
+            ],
+            selectDartPluginsOnly: true,
+          );
         },
             throwsToolExit(
               message: 'Please resolve the plugin pubspec errors',
@@ -735,13 +772,189 @@ void main() {
             '\n\n');
       });
 
+      testUsingContext('provides warning when a plugin references a default plugin without implementation', () async {
+        final Set<String> directDependencies = <String>{'url_launcher'};
+        final List<PluginInterfaceResolution> resolutions =
+            resolvePlatformImplementation(
+          <Plugin>[
+            Plugin.fromYaml(
+              'url_launcher',
+              '',
+              YamlMap.wrap(<String, dynamic>{
+                'platforms': <String, dynamic>{
+                  'linux': <String, dynamic>{
+                    'default_package': 'url_launcher_linux',
+                  },
+                },
+              }),
+              null,
+              <String>[],
+              fileSystem: fs,
+              appDependencies: directDependencies,
+            ),
+            Plugin.fromYaml(
+              'url_launcher_linux',
+              '',
+              YamlMap.wrap(<String, dynamic>{
+                'implements': 'url_launcher',
+                'platforms': <String, dynamic>{},
+              }),
+              null,
+              <String>[],
+              fileSystem: fs,
+              appDependencies: directDependencies,
+            ),
+          ],
+          selectDartPluginsOnly: true,
+        );
+
+        expect(resolutions.length, equals(0));
+        expect(
+            testLogger.warningText,
+            'Package url_launcher:linux references url_launcher_linux:linux as the default plugin, '
+            'but it does not provide an inline implementation.\n'
+            'Ask the maintainers of url_launcher to either avoid referencing a default implementation via `platforms: linux: default_package: url_launcher_linux` '
+            'or add an inline implementation to url_launcher_linux via `platforms: linux:` `pluginClass` or `dartPluginClass`.\n'
+            '\n');
+      });
+
+      testUsingContext('avoid warning when a plugin references a default plugin with a native implementation only', () async {
+        final Set<String> directDependencies = <String>{'url_launcher'};
+        final List<PluginInterfaceResolution> resolutions =
+        resolvePlatformImplementation(
+          <Plugin>[
+            Plugin.fromYaml(
+              'url_launcher',
+              '',
+              YamlMap.wrap(<String, dynamic>{
+                'platforms': <String, dynamic>{
+                  'linux': <String, dynamic>{
+                    'default_package': 'url_launcher_linux',
+                  },
+                },
+              }),
+              null,
+              <String>[],
+              fileSystem: fs,
+              appDependencies: directDependencies,
+            ),
+            Plugin.fromYaml(
+              'url_launcher_linux',
+              '',
+              YamlMap.wrap(<String, dynamic>{
+                'implements': 'url_launcher',
+                'platforms': <String, dynamic>{
+                  'linux': <String, dynamic>{
+                    'pluginClass': 'UrlLauncherLinux',
+                  },
+                },
+              }),
+              null,
+              <String>[],
+              fileSystem: fs,
+              appDependencies: directDependencies,
+            ),
+          ],
+          selectDartPluginsOnly: true,
+        );
+
+        expect(resolutions.length, equals(0));
+        expect(testLogger.warningText, '');
+      });
+
+      testUsingContext('selects default Dart implementation without warning, while choosing plugin selection for nativeOrDart', () async {
+        final Set<String> directDependencies = <String>{'url_launcher'};
+        final List<PluginInterfaceResolution> resolutions = resolvePlatformImplementation(
+          <Plugin>[
+            Plugin.fromYaml(
+              'url_launcher',
+              '',
+              YamlMap.wrap(<String, dynamic>{
+                'platforms': <String, dynamic>{
+                  'linux': <String, dynamic>{
+                    'default_package': 'url_launcher_linux',
+                  },
+                },
+              }),
+              null,
+              <String>[],
+              fileSystem: fs,
+              appDependencies: directDependencies,
+            ),
+            Plugin.fromYaml(
+              'url_launcher_linux',
+              '',
+              YamlMap.wrap(<String, dynamic>{
+                'implements': 'url_launcher',
+                'platforms': <String, dynamic>{
+                  'linux': <String, dynamic>{
+                    'dartPluginClass': 'UrlLauncherLinux',
+                  },
+                },
+              }),
+              null,
+              <String>[],
+              fileSystem: fs,
+              appDependencies: directDependencies,
+            ),
+          ],
+          // Using nativeOrDart plugin selection.
+          selectDartPluginsOnly: false,
+        );
+        expect(resolutions.length, equals(1));
+        // Test avoiding trigger a warning for default plugins, while Dart and native plugins selection is enabled.
+        expect(testLogger.warningText, '');
+        expect(resolutions[0].toMap(), equals(
+            <String, String>{
+              'pluginName': 'url_launcher_linux',
+              'dartClass': 'UrlLauncherLinux',
+              'platform': 'linux',
+            })
+        );
+      });
+
+      testUsingContext('provides warning when a plugin references a default plugin which does not exist', () async {
+        final Set<String> directDependencies = <String>{'url_launcher'};
+        final List<PluginInterfaceResolution> resolutions =
+            resolvePlatformImplementation(
+          <Plugin>[
+            Plugin.fromYaml(
+              'url_launcher',
+              '',
+              YamlMap.wrap(<String, dynamic>{
+                'platforms': <String, dynamic>{
+                  'linux': <String, dynamic>{
+                    'default_package': 'url_launcher_linux',
+                  },
+                },
+              }),
+              null,
+              <String>[],
+              fileSystem: fs,
+              appDependencies: directDependencies,
+            ),
+          ],
+          selectDartPluginsOnly: true,
+        );
+
+        expect(resolutions.length, equals(0));
+        expect(
+            testLogger.warningText,
+            'Package url_launcher:linux references url_launcher_linux:linux as the default plugin, '
+            'but the package does not exist.\n'
+            'Ask the maintainers of url_launcher to either avoid referencing a default implementation via `platforms: linux: default_package: url_launcher_linux` '
+            'or create a plugin named url_launcher_linux.\n'
+            '\n');
+      });
+
       testUsingContext('provides error when user selected multiple implementations', () async {
         final Set<String> directDependencies = <String>{
           'url_launcher_linux_1',
           'url_launcher_linux_2',
         };
         expect(() {
-          resolvePlatformImplementation(<Plugin>[
+          resolvePlatformImplementation(
+            <Plugin>[
               Plugin.fromYaml(
                 'url_launcher_linux_1',
                 '',
@@ -774,8 +987,9 @@ void main() {
                 fileSystem: fs,
                 appDependencies: directDependencies,
               ),
-          ]);
+            ],
-
+            selectDartPluginsOnly: true,
+          );
         },
         throwsToolExit(
           message: 'Please resolve the plugin implementation selection errors',
@@ -786,8 +1000,8 @@ void main() {
           'Plugin url_launcher:linux has conflicting direct dependency implementations:\n'
           '  url_launcher_linux_1\n'
           '  url_launcher_linux_2\n'
-          'To fix this issue, remove all but one of these dependencies from pubspec.yaml.'
+          'To fix this issue, remove all but one of these dependencies from pubspec.yaml.\n'
-          '\n\n'
+          '\n'
         );
       });
 
@@ -799,7 +1013,8 @@ void main() {
           'url_launcher_windows_2',
         };
         expect(() {
-          resolvePlatformImplementation(<Plugin>[
+          resolvePlatformImplementation(
+            <Plugin>[
               Plugin.fromYaml(
                 'url_launcher_linux_1',
                 '',
@@ -864,7 +1079,9 @@ void main() {
                 fileSystem: fs,
                 appDependencies: directDependencies,
               ),
-          ]);
+            ],
+            selectDartPluginsOnly: true,
+          );
         },
         throwsToolExit(
           message: 'Please resolve the plugin implementation selection errors',
@@ -875,20 +1092,21 @@ void main() {
           'Plugin url_launcher:linux has conflicting direct dependency implementations:\n'
           '  url_launcher_linux_1\n'
           '  url_launcher_linux_2\n'
-          'To fix this issue, remove all but one of these dependencies from pubspec.yaml.'
+          'To fix this issue, remove all but one of these dependencies from pubspec.yaml.\n'
-          '\n\n'
+          '\n'
           'Plugin url_launcher:windows has conflicting direct dependency implementations:\n'
           '  url_launcher_windows_1\n'
           '  url_launcher_windows_2\n'
-          'To fix this issue, remove all but one of these dependencies from pubspec.yaml.'
+          'To fix this issue, remove all but one of these dependencies from pubspec.yaml.\n'
-          '\n\n'
+          '\n'
         );
       });
 
       testUsingContext('provides error when user needs to select among multiple implementations', () async {
         final Set<String> directDependencies = <String>{};
         expect(() {
-          resolvePlatformImplementation(<Plugin>[
+          resolvePlatformImplementation(
+            <Plugin>[
               Plugin.fromYaml(
                 'url_launcher_linux_1',
                 '',
@@ -921,7 +1139,9 @@ void main() {
                 fileSystem: fs,
                 appDependencies: directDependencies,
               ),
-          ]);
+            ],
+            selectDartPluginsOnly: true,
+          );
         },
         throwsToolExit(
           message: 'Please resolve the plugin implementation selection errors',
@@ -932,8 +1152,8 @@ void main() {
           'Plugin url_launcher:linux has multiple possible implementations:\n'
           '  url_launcher_linux_1\n'
           '  url_launcher_linux_2\n'
-          'To fix this issue, add one of these dependencies to pubspec.yaml.'
+          'To fix this issue, add one of these dependencies to pubspec.yaml.\n'
-          '\n\n'
+          '\n',
         );
       });
     });

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';
@@ -892,6 +893,7 @@ dependencies:
         ProcessManager: () => FakeProcessManager.any(),
       });
 
+      group('Build time plugin injection', () {
         testUsingContext("Registrant for web doesn't escape slashes in imports", () async {
           flutterProject.isModule = true;
           final Directory webPluginWithNestedFile =
@@ -930,6 +932,61 @@ web_plugin_with_nested:${webPluginWithNestedFile.childDirectory('lib').uri}
           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 {
         // Create a plugin without a pluginClass.
         final Directory pluginDirectory = createFakePlugin(fs);
@@ -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]');