Temporarily allow pluginClass: none on desktop (#57498)

Treats 'pluginClass: none' as equivalent to having no 'pluginClass'
entry on the desktop platforms, to satisy stable channel plugin
validation of Dart-only desktop plugin implementations. See
issue for full details.

Part of https://github.com/flutter/flutter/issues/57497

packages/flutter_tools/lib/src/platform_plugins.dart

@@ -214,9 +214,14 @@ class MacOSPlugin extends PluginPlatform implements NativeOrDartPlugin {
 
   factory MacOSPlugin.fromYaml(String name, YamlMap yaml) {
     assert(validate(yaml));
+    // Treat 'none' as not present. See https://github.com/flutter/flutter/issues/57497.
+    String pluginClass = yaml[kPluginClass] as String;
+    if (pluginClass == 'none') {
+      pluginClass = null;
+    }
     return MacOSPlugin(
       name: name,
-      pluginClass: yaml[kPluginClass] as String,
+      pluginClass: pluginClass,
       dartPluginClass: yaml[kDartPluginClass] as String,
     );
   }
@@ -260,9 +265,14 @@ class WindowsPlugin extends PluginPlatform implements NativeOrDartPlugin{
 
   factory WindowsPlugin.fromYaml(String name, YamlMap yaml) {
     assert(validate(yaml));
+    // Treat 'none' as not present. See https://github.com/flutter/flutter/issues/57497.
+    String pluginClass = yaml[kPluginClass] as String;
+    if (pluginClass == 'none') {
+      pluginClass = null;
+    }
     return WindowsPlugin(
       name: name,
-      pluginClass: yaml[kPluginClass] as String,
+      pluginClass: pluginClass,
       dartPluginClass: yaml[kDartPluginClass] as String,
     );
   }
@@ -307,9 +317,14 @@ class LinuxPlugin extends PluginPlatform implements NativeOrDartPlugin {
 
   factory LinuxPlugin.fromYaml(String name, YamlMap yaml) {
     assert(validate(yaml));
+    // Treat 'none' as not present. See https://github.com/flutter/flutter/issues/57497.
+    String pluginClass = yaml[kPluginClass] as String;
+    if (pluginClass == 'none') {
+      pluginClass = null;
+    }
     return LinuxPlugin(
       name: name,
-      pluginClass: yaml[kPluginClass] as String,
+      pluginClass: pluginClass,
       dartPluginClass: yaml[kDartPluginClass] as String,
     );
   }

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

@@ -914,6 +914,35 @@ flutter:
         FeatureFlags: () => featureFlags,
       });
 
+      testUsingContext('pluginClass: none doesn\'t trigger registrant entry on macOS', () async {
+        when(macosProject.existsSync()).thenReturn(true);
+        when(featureFlags.isMacOSEnabled).thenReturn(true);
+        when(flutterProject.isModule).thenReturn(true);
+        // Create a plugin without a pluginClass.
+        dummyPackageDirectory.parent.childFile('pubspec.yaml')
+          ..createSync(recursive: true)
+          ..writeAsStringSync('''
+flutter:
+  plugin:
+    platforms:
+      macos:
+        pluginClass: none
+        dartPluginClass: SomePlugin
+    ''');
+
+        await injectPlugins(flutterProject, checkProjects: true);
+
+        final File registrantFile = macosProject.managedDirectory.childFile('GeneratedPluginRegistrant.swift');
+
+        expect(registrantFile, exists);
+        expect(registrantFile, isNot(contains('SomePlugin')));
+        expect(registrantFile, isNot(contains('none')));
+      }, overrides: <Type, Generator>{
+        FileSystem: () => fs,
+        ProcessManager: () => FakeProcessManager.any(),
+        FeatureFlags: () => featureFlags,
+      });
+
       testUsingContext('Injecting creates generated Linux registrant', () async {
         when(linuxProject.existsSync()).thenReturn(true);
         when(featureFlags.isLinuxEnabled).thenReturn(true);
@@ -961,6 +990,35 @@ flutter:
         FeatureFlags: () => featureFlags,
       });
 
+      testUsingContext('pluginClass: none doesn\'t trigger registrant entry on Linux', () async {
+        when(linuxProject.existsSync()).thenReturn(true);
+        when(featureFlags.isLinuxEnabled).thenReturn(true);
+        when(flutterProject.isModule).thenReturn(false);
+        // Create a plugin without a pluginClass.
+        dummyPackageDirectory.parent.childFile('pubspec.yaml')
+          ..createSync(recursive: true)
+          ..writeAsStringSync('''
+flutter:
+  plugin:
+    platforms:
+      linux:
+        pluginClass: none
+        dartPluginClass: SomePlugin
+    ''');
+
+        await injectPlugins(flutterProject, checkProjects: true);
+
+        final File registrantImpl = linuxProject.managedDirectory.childFile('generated_plugin_registrant.cc');
+
+        expect(registrantImpl, exists);
+        expect(registrantImpl, isNot(contains('SomePlugin')));
+        expect(registrantImpl, isNot(contains('none')));
+      }, overrides: <Type, Generator>{
+        FileSystem: () => fs,
+        ProcessManager: () => FakeProcessManager.any(),
+        FeatureFlags: () => featureFlags,
+      });
+
       testUsingContext('Injecting creates generated Linux plugin Cmake file', () async {
         when(linuxProject.existsSync()).thenReturn(true);
         when(featureFlags.isLinuxEnabled).thenReturn(true);
@@ -1034,6 +1092,38 @@ flutter:
         FeatureFlags: () => featureFlags,
       });
 
+      testUsingContext('pluginClass: none doesn\'t trigger registrant entry on Windows', () async {
+        when(windowsProject.existsSync()).thenReturn(true);
+        when(featureFlags.isWindowsEnabled).thenReturn(true);
+        when(flutterProject.isModule).thenReturn(false);
+        // Create a plugin without a pluginClass.
+        dummyPackageDirectory.parent.childFile('pubspec.yaml')
+          ..createSync(recursive: true)
+          ..writeAsStringSync('''
+flutter:
+  plugin:
+    platforms:
+      windows:
+        pluginClass: none
+        dartPluginClass: SomePlugin
+    ''');
+
+        createDummyWindowsSolutionFile();
+        createDummyPluginWindowsProjectFile();
+
+        await injectPlugins(flutterProject, checkProjects: true);
+
+        final File registrantImpl = windowsProject.managedDirectory.childFile('generated_plugin_registrant.cc');
+
+        expect(registrantImpl, exists);
+        expect(registrantImpl, isNot(contains('SomePlugin')));
+        expect(registrantImpl, isNot(contains('none')));
+      }, overrides: <Type, Generator>{
+        FileSystem: () => fs,
+        ProcessManager: () => FakeProcessManager.any(),
+        FeatureFlags: () => featureFlags,
+      });
+
       testUsingContext('Injecting creates generated Windows plugin properties', () async {
         when(windowsProject.existsSync()).thenReturn(true);
         when(featureFlags.isWindowsEnabled).thenReturn(true);