Enable Dart plugin registrant on Desktop only (#81586)

packages/flutter_tools/lib/src/build_system/targets/dart_plugin_registrant.dart

@@ -8,6 +8,7 @@ import 'package:meta/meta.dart';
 import 'package:package_config/package_config.dart';
 
 import '../../base/file_system.dart';
+import '../../build_info.dart';
 import '../../dart/package_map.dart';
 import '../../flutter_plugins.dart';
 import '../../project.dart';
@@ -63,7 +64,21 @@ class DartPluginRegistrantTarget extends Target {
 
   @override
   bool canSkip(Environment environment) {
-    return !environment.generateDartPluginRegistry;
+    if (!environment.generateDartPluginRegistry) {
+      return true;
+    }
+    final String platformName = environment.defines[kTargetPlatform];
+    if (platformName == null) {
+      return true;
+    }
+    final TargetPlatform targetPlatform = getTargetPlatformForName(platformName);
+    // TODO(egarciad): Support Android and iOS.
+    // https://github.com/flutter/flutter/issues/52267
+    return targetPlatform != TargetPlatform.darwin &&
+           targetPlatform != TargetPlatform.linux_x64 &&
+           targetPlatform != TargetPlatform.linux_arm64 &&
+           targetPlatform != TargetPlatform.windows_x64 &&
+           targetPlatform != TargetPlatform.windows_uwp_x64;
   }
 
   @override

packages/flutter_tools/test/general.shard/build_system/targets/dart_plugin_registrant_test.dart

@@ -104,9 +104,12 @@ void main() {
           fileSystem: fileSystem,
           logger: BufferLogger.test(),
           processManager: FakeProcessManager.any(),
-          generateDartPluginRegistry: false);
+          generateDartPluginRegistry: false,
+          defines: <String, String>{
+            kTargetPlatform: 'darwin-x64',
+          });
 
-      expect(const DartPluginRegistrantTarget().canSkip(environment), true);
+      expect(const DartPluginRegistrantTarget().canSkip(environment), isTrue);
 
       final Environment environment2 = Environment.test(
           fileSystem.currentDirectory,
@@ -114,9 +117,46 @@ void main() {
           fileSystem: fileSystem,
           logger: BufferLogger.test(),
           processManager: FakeProcessManager.any(),
-          generateDartPluginRegistry: true);
+          generateDartPluginRegistry: true,
+          defines: <String, String>{
+            kTargetPlatform: 'darwin-x64',
+          });
+
+      expect(const DartPluginRegistrantTarget().canSkip(environment2), isFalse);
+    });
 
-      expect(const DartPluginRegistrantTarget().canSkip(environment2), false);
+    testWithoutContext('skipped based on platform', () async {
+      const Map<String, bool> canSkip = <String, bool>{
+        'darwin-x64': false,
+        'linux-x64': false,
+        'linux-arm64': false,
+        'windows-x64': false,
+        'windows-uwp-x64': false,
+        'web-javascript': true,
+        'ios': true,
+        'android': true,
+        'fuchsia-arm64': true,
+        'fuchsia-x64': true,
+      };
+
+      for (final String targetPlatform in canSkip.keys) {
+        expect(
+          const DartPluginRegistrantTarget().canSkip(
+            Environment.test(
+              fileSystem.currentDirectory,
+              artifacts: null,
+              fileSystem: fileSystem,
+              logger: BufferLogger.test(),
+              processManager: FakeProcessManager.any(),
+              generateDartPluginRegistry: true,
+              defines: <String, String>{
+                kTargetPlatform: targetPlatform,
+              },
+            ),
+          ),
+          canSkip[targetPlatform],
+        );
+      }
     });
 
     testUsingContext("doesn't generate generated_main.dart if there aren't Dart plugins", () async {