[flutter_tools] pass through enable impeller flag to macOS. (flutter#128720)

Allow passing through the --enable-impeller flag to macOS.

Author: Jonah Williams

packages/flutter_tools/lib/src/desktop_device.dart

@@ -209,6 +209,8 @@ abstract class DesktopDevice extends Device {
   /// steps to be run.
   void onAttached(ApplicationPackage package, BuildInfo buildInfo, Process process) {}
 
+  bool get supportsImpeller => false;
+
   /// Computes a set of environment variables used to pass debugging information
   /// to the engine without interfering with application level command line
   /// arguments.
@@ -266,6 +268,15 @@ abstract class DesktopDevice extends Device {
     if (debuggingOptions.purgePersistentCache) {
       addFlag('purge-persistent-cache=true');
     }
+    if (supportsImpeller) {
+      switch (debuggingOptions.enableImpeller) {
+        case ImpellerStatus.enabled:
+          addFlag('enable-impeller=true');
+        case ImpellerStatus.disabled:
+        case ImpellerStatus.platformDefault:
+          addFlag('enable-impeller=false');
+      }
+    }
     // Options only supported when there is a VM Service connection between the
     // tool and the device, usually in debug or profile mode.
     if (debuggingOptions.debuggingEnabled) {

packages/flutter_tools/lib/src/macos/macos_device.dart

@@ -47,16 +47,18 @@ class MacOSDevice extends DesktopDevice {
   @override
   String get name => 'macOS';
 
+  @override
+  bool get supportsImpeller => true;
+
   @override
   Future<TargetPlatform> get targetPlatform async => TargetPlatform.darwin;
 
   @override
   Future<String> get targetPlatformDisplayName async {
     if (_operatingSystemUtils.hostPlatform == HostPlatform.darwin_arm64) {
       return 'darwin-arm64';
-    } else {
-      return 'darwin-x64';
     }
+    return 'darwin-x64';
   }
 
   @override

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

@@ -300,6 +300,66 @@ void main() {
       ),
     );
   });
+
+  testWithoutContext('Desktop devices that support impeller pass through the enable-impeller flag', () async {
+    final FakeProcessManager processManager = FakeProcessManager.list(<FakeCommand>[
+      const FakeCommand(
+        command: <String>['debug'],
+        exitCode: -1,
+        environment: <String, String>{
+          'FLUTTER_ENGINE_SWITCH_1': 'enable-dart-profiling=true',
+          'FLUTTER_ENGINE_SWITCH_2': 'enable-impeller=true',
+          'FLUTTER_ENGINE_SWITCH_3': 'enable-checked-mode=true',
+          'FLUTTER_ENGINE_SWITCH_4': 'verify-entry-points=true',
+          'FLUTTER_ENGINE_SWITCHES': '4'
+        }
+      ),
+    ]);
+    final FakeDesktopDevice device = setUpDesktopDevice(
+      processManager: processManager,
+      supportsImpeller: true,
+    );
+
+    final FakeApplicationPackage package = FakeApplicationPackage();
+    await device.startApp(
+      package,
+      prebuiltApplication: true,
+      debuggingOptions: DebuggingOptions.enabled(
+        BuildInfo.debug,
+        enableImpeller: ImpellerStatus.enabled,
+        dartEntrypointArgs: <String>[],
+      ),
+    );
+  });
+
+  testWithoutContext('Desktop devices that do not support impeller ignore the enable-impeller flag', () async {
+    final FakeProcessManager processManager = FakeProcessManager.list(<FakeCommand>[
+      const FakeCommand(
+        command: <String>['debug'],
+        exitCode: -1,
+        environment: <String, String>{
+          'FLUTTER_ENGINE_SWITCH_1': 'enable-dart-profiling=true',
+          'FLUTTER_ENGINE_SWITCH_2': 'enable-checked-mode=true',
+          'FLUTTER_ENGINE_SWITCH_3': 'verify-entry-points=true',
+          'FLUTTER_ENGINE_SWITCHES': '3'
+        }
+      ),
+    ]);
+    final FakeDesktopDevice device = setUpDesktopDevice(
+      processManager: processManager,
+    );
+
+    final FakeApplicationPackage package = FakeApplicationPackage();
+    await device.startApp(
+      package,
+      prebuiltApplication: true,
+      debuggingOptions: DebuggingOptions.enabled(
+        BuildInfo.debug,
+        enableImpeller: ImpellerStatus.enabled,
+        dartEntrypointArgs: <String>[],
+      ),
+    );
+  });
 }
 
 FakeDesktopDevice setUpDesktopDevice({
@@ -308,13 +368,15 @@ FakeDesktopDevice setUpDesktopDevice({
   ProcessManager? processManager,
   OperatingSystemUtils? operatingSystemUtils,
   bool nullExecutablePathForDevice = false,
+  bool supportsImpeller = false,
 }) {
   return FakeDesktopDevice(
     fileSystem: fileSystem ?? MemoryFileSystem.test(),
     logger: logger ?? BufferLogger.test(),
     processManager: processManager ?? FakeProcessManager.any(),
     operatingSystemUtils: operatingSystemUtils ?? FakeOperatingSystemUtils(),
     nullExecutablePathForDevice: nullExecutablePathForDevice,
+    supportsImpeller: supportsImpeller,
   );
 }
 
@@ -326,6 +388,7 @@ class FakeDesktopDevice extends DesktopDevice {
     required FileSystem fileSystem,
     required OperatingSystemUtils operatingSystemUtils,
     this.nullExecutablePathForDevice = false,
+    this.supportsImpeller = false,
   }) : super(
       'dummy',
       platformType: PlatformType.linux,
@@ -344,6 +407,9 @@ class FakeDesktopDevice extends DesktopDevice {
 
   final bool nullExecutablePathForDevice;
 
+  @override
+  final bool supportsImpeller;
+
   @override
   String get name => 'dummy';