Always invoke impeller ios shader target (#114451)

Author: Jonah Williams

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

@@ -511,22 +511,14 @@ abstract class IosAssetBundle extends Target {
 
     final FlutterProject flutterProject = FlutterProject.fromDirectory(environment.projectDir);
 
-    bool isImpellerEnabled() {
-      if (!flutterProject.ios.infoPlist.existsSync()) {
-        return false;
-      }
-      final Map<String, Object> info = globals.plistParser.parseFile(flutterProject.ios.infoPlist.path);
-
-      final Object? enableImpeller = info['FLTEnableImpeller'];
-      return enableImpeller is bool && enableImpeller;
-    }
-
     // Copy the assets.
     final Depfile assetDepfile = await copyAssets(
       environment,
       assetDirectory,
       targetPlatform: TargetPlatform.ios,
-      shaderTarget: isImpellerEnabled() ? ShaderTarget.impelleriOS : ShaderTarget.sksl,
+      // Always specify an impeller shader target so that we support runtime toggling and
+      // the --enable-impeller debug flag.
+      shaderTarget: ShaderTarget.impelleriOS,
       additionalInputs: <File>[
         flutterProject.ios.infoPlist,
         flutterProject.ios.appFrameworkInfoPlist,

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

@@ -217,6 +217,78 @@ void main() {
     expect(assetDirectory.childFile('isolate_snapshot_data'), exists);
     expect(assetDirectory.childFile('io.flutter.shaders.json'), exists);
     expect(assetDirectory.childFile('io.flutter.shaders.json').readAsStringSync(), '{"data":{"A":"B"}}');
+  }, overrides: <Type, Generator>{
+    FileSystem: () => fileSystem,
+    ProcessManager: () => processManager,
+    Platform: () => macPlatform,
+  });
+
+  testUsingContext('DebugIosApplicationBundle with impeller and shader compilation', () async {
+    // Create impellerc to work around fallback detection logic.
+    fileSystem.file(artifacts.getHostArtifact(HostArtifact.impellerc)).createSync(recursive: true);
+
+    environment.defines[kBuildMode] = 'debug';
+    environment.defines[kCodesignIdentity] = 'ABC123';
+    // Precompiled dart data
+
+    fileSystem.file(artifacts.getArtifactPath(Artifact.vmSnapshotData, mode: BuildMode.debug))
+      .createSync();
+    fileSystem.file(artifacts.getArtifactPath(Artifact.isolateSnapshotData, mode: BuildMode.debug))
+      .createSync();
+    // Project info
+    fileSystem.file('pubspec.yaml').writeAsStringSync('name: hello\nflutter:\n  shaders:\n    - shader.glsl');
+    fileSystem.file('.packages').writeAsStringSync('\n');
+    // Plist file
+    fileSystem.file(fileSystem.path.join('ios', 'Flutter', 'AppFrameworkInfo.plist'))
+      .createSync(recursive: true);
+    // Shader file
+    fileSystem.file('shader.glsl').writeAsStringSync('test');
+    // App kernel
+    environment.buildDir.childFile('app.dill').createSync(recursive: true);
+    // Stub framework
+    environment.buildDir
+        .childDirectory('App.framework')
+      .childFile('App')
+      .createSync(recursive: true);
+
+    final Directory frameworkDirectory = environment.outputDir.childDirectory('App.framework');
+    final File frameworkDirectoryBinary = frameworkDirectory.childFile('App');
+    processManager.addCommands(<FakeCommand>[
+      const FakeCommand(command: <String>[
+        'HostArtifact.impellerc',
+        '--runtime-stage-metal',
+        '--iplr',
+        '--sl=/App.framework/flutter_assets/shader.glsl',
+        '--spirv=/App.framework/flutter_assets/shader.glsl.spirv',
+        '--input=/shader.glsl',
+        '--input-type=frag',
+        '--include=/'
+      ]),
+      FakeCommand(command: <String>[
+        'codesign',
+        '--force',
+        '--sign',
+        'ABC123',
+        '--timestamp=none',
+        frameworkDirectoryBinary.path,
+      ]),
+    ]);
+
+    await const DebugIosApplicationBundle().build(environment);
+    expect(processManager, hasNoRemainingExpectations);
+
+    expect(frameworkDirectoryBinary, exists);
+    expect(frameworkDirectory.childFile('Info.plist'), exists);
+
+    final Directory assetDirectory = frameworkDirectory.childDirectory('flutter_assets');
+    expect(assetDirectory.childFile('kernel_blob.bin'), exists);
+    expect(assetDirectory.childFile('AssetManifest.json'), exists);
+    expect(assetDirectory.childFile('vm_snapshot_data'), exists);
+    expect(assetDirectory.childFile('isolate_snapshot_data'), exists);
+  }, overrides: <Type, Generator>{
+    FileSystem: () => fileSystem,
+    ProcessManager: () => processManager,
+    Platform: () => macPlatform,
   });
 
   testUsingContext('ReleaseIosApplicationBundle build', () async {