[reland] Support conditional bundling of assets based on `--flavor` (#139834)

Reland of https://github.com/flutter/flutter/pull/132985. Fixes the path to AssetManifest.bin in flavors_test_ios

dev/bots/pubspec.yaml

@@ -58,6 +58,7 @@ dependencies:
   source_maps: 0.10.12 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   source_span: 1.10.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   stack_trace: 1.11.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
+  standard_message_codec: 0.0.1+4 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   stream_channel: 2.1.2 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   string_scanner: 1.2.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   term_glyph: 1.2.1 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
@@ -74,4 +75,4 @@ dependencies:
 dev_dependencies:
   test_api: 0.6.1
 
-# PUBSPEC CHECKSUM: 29d2
+# PUBSPEC CHECKSUM: b875

dev/devicelab/bin/tasks/flavors_test.dart

@@ -2,12 +2,17 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:io' show File;
+import 'dart:typed_data';
+
+import 'package:collection/collection.dart';
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/framework/task_result.dart';
 import 'package:flutter_devicelab/framework/utils.dart';
 import 'package:flutter_devicelab/tasks/integration_tests.dart';
 import 'package:path/path.dart' as path;
+import 'package:standard_message_codec/standard_message_codec.dart';
 
 Future<void> main() async {
   deviceOperatingSystem = DeviceOperatingSystem.android;
@@ -15,31 +20,20 @@ Future<void> main() async {
     await createFlavorsTest().call();
     await createIntegrationTestFlavorsTest().call();
 
+    final String projectPath = '${flutterDirectory.path}/dev/integration_tests/flavors';
     final TaskResult installTestsResult = await inDirectory(
-      '${flutterDirectory.path}/dev/integration_tests/flavors',
+      projectPath,
       () async {
-        await flutter(
-          'install',
-          options: <String>['--debug', '--flavor', 'paid'],
-        );
-        await flutter(
-          'install',
-          options: <String>['--debug', '--flavor', 'paid', '--uninstall-only'],
-        );
-
-        final StringBuffer stderr = StringBuffer();
-        await evalFlutter(
-          'install',
-          canFail: true,
-          stderr: stderr,
-          options: <String>['--flavor', 'bogus'],
-        );
-
-        final String stderrString = stderr.toString();
-        final String expectedApkPath = path.join('build', 'app', 'outputs', 'flutter-apk', 'app-bogus-release.apk');
-        if (!stderrString.contains('"$expectedApkPath" does not exist.')) {
-          print(stderrString);
-          return TaskResult.failure('Should not succeed with bogus flavor');
+        final List<TaskResult> testResults = <TaskResult>[
+          await _testInstallDebugPaidFlavor(projectPath),
+          await _testInstallBogusFlavor(),
+        ];
+
+        final TaskResult? firstInstallFailure = testResults
+          .firstWhereOrNull((TaskResult element) => element.failed);
+
+        if (firstInstallFailure != null) {
+          return firstInstallFailure;
         }
 
         return TaskResult.success(null);
@@ -49,3 +43,49 @@ Future<void> main() async {
     return installTestsResult;
   });
 }
+
+// Ensures installation works. Also tests asset bundling while we are at it.
+Future<TaskResult> _testInstallDebugPaidFlavor(String projectDir) async {
+  await evalFlutter(
+    'install',
+    options: <String>['--debug', '--flavor', 'paid'],
+  );
+
+  final Uint8List assetManifestFileData = File(
+    path.join(projectDir, 'build', 'app', 'intermediates', 'assets', 'paidDebug', 'flutter_assets', 'AssetManifest.bin'),
+  ).readAsBytesSync();
+
+  final Map<Object?, Object?> assetManifest = const StandardMessageCodec()
+    .decodeMessage(ByteData.sublistView(assetManifestFileData)) as Map<Object?, Object?>;
+
+  if (assetManifest.containsKey('assets/free/free.txt')) {
+    return TaskResult.failure('Assets declared with a flavor not equal to the '
+      'argued --flavor value should not be bundled.');
+  }
+
+  await flutter(
+    'install',
+    options: <String>['--debug', '--flavor', 'paid', '--uninstall-only'],
+  );
+
+  return TaskResult.success(null);
+}
+
+Future<TaskResult> _testInstallBogusFlavor() async {
+  final StringBuffer stderr = StringBuffer();
+  await evalFlutter(
+    'install',
+    canFail: true,
+    stderr: stderr,
+    options: <String>['--flavor', 'bogus'],
+  );
+
+  final String stderrString = stderr.toString();
+  final String expectedApkPath = path.join('build', 'app', 'outputs', 'flutter-apk', 'app-bogus-release.apk');
+  if (!stderrString.contains('"$expectedApkPath" does not exist.')) {
+    print(stderrString);
+    return TaskResult.failure('Should not succeed with bogus flavor');
+  }
+
+  return TaskResult.success(null);
+}

dev/devicelab/bin/tasks/flavors_test_ios.dart

@@ -2,11 +2,17 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'dart:io';
+import 'dart:typed_data';
+
+import 'package:collection/collection.dart';
 import 'package:flutter_devicelab/framework/devices.dart';
 import 'package:flutter_devicelab/framework/framework.dart';
 import 'package:flutter_devicelab/framework/task_result.dart';
 import 'package:flutter_devicelab/framework/utils.dart';
 import 'package:flutter_devicelab/tasks/integration_tests.dart';
+import 'package:path/path.dart' as path;
+import 'package:standard_message_codec/standard_message_codec.dart';
 
 Future<void> main() async {
   deviceOperatingSystem = DeviceOperatingSystem.ios;
@@ -14,29 +20,20 @@ Future<void> main() async {
     await createFlavorsTest().call();
     await createIntegrationTestFlavorsTest().call();
     // test install and uninstall of flavors app
+    final String projectDir = '${flutterDirectory.path}/dev/integration_tests/flavors';
     final TaskResult installTestsResult = await inDirectory(
-      '${flutterDirectory.path}/dev/integration_tests/flavors',
+      projectDir,
       () async {
-        await flutter(
-          'install',
-          options: <String>['--flavor', 'paid'],
-        );
-        await flutter(
-          'install',
-          options: <String>['--flavor', 'paid', '--uninstall-only'],
-        );
-        final StringBuffer stderr = StringBuffer();
-        await evalFlutter(
-          'install',
-          canFail: true,
-          stderr: stderr,
-          options: <String>['--flavor', 'bogus'],
-        );
-
-        final String stderrString = stderr.toString();
-        if (!stderrString.contains('The Xcode project defines schemes: free, paid')) {
-          print(stderrString);
-          return TaskResult.failure('Should not succeed with bogus flavor');
+        final List<TaskResult> testResults = <TaskResult>[
+            await _testInstallDebugPaidFlavor(projectDir),
+            await _testInstallBogusFlavor(),
+        ];
+
+        final TaskResult? firstInstallFailure = testResults
+          .firstWhereOrNull((TaskResult element) => element.failed);
+
+        if (firstInstallFailure != null) {
+          return firstInstallFailure;
         }
 
         return TaskResult.success(null);
@@ -46,3 +43,56 @@ Future<void> main() async {
     return installTestsResult;
   });
 }
+
+Future<TaskResult> _testInstallDebugPaidFlavor(String projectDir) async {
+  await evalFlutter(
+    'install',
+    options: <String>['--flavor', 'paid'],
+  );
+  final Uint8List assetManifestFileData = File(
+    path.join(
+      projectDir,
+      'build',
+      'ios',
+      'iphoneos',
+      'Paid App.app',
+      'Frameworks',
+      'App.framework',
+      'flutter_assets',
+      'AssetManifest.bin',
+    ),
+  ).readAsBytesSync();
+
+  final Map<Object?, Object?> assetManifest = const StandardMessageCodec()
+    .decodeMessage(ByteData.sublistView(assetManifestFileData)) as Map<Object?, Object?>;
+
+  if (assetManifest.containsKey('assets/free/free.txt')) {
+    return TaskResult.failure('Assets declared with a flavor not equal to the '
+      'argued --flavor value should not be bundled.');
+  }
+
+  await flutter(
+    'install',
+    options: <String>['--flavor', 'paid', '--uninstall-only'],
+  );
+
+  return TaskResult.success(null);
+}
+
+Future<TaskResult> _testInstallBogusFlavor() async {
+  final StringBuffer stderr = StringBuffer();
+  await evalFlutter(
+    'install',
+    canFail: true,
+    stderr: stderr,
+    options: <String>['--flavor', 'bogus'],
+  );
+
+  final String stderrString = stderr.toString();
+  if (!stderrString.contains('The Xcode project defines schemes: free, paid')) {
+    print(stderrString);
+    return TaskResult.failure('Should not succeed with bogus flavor');
+  }
+
+  return TaskResult.success(null);
+}

dev/devicelab/pubspec.yaml

@@ -24,6 +24,7 @@ dependencies:
   web: 0.4.0
   webkit_inspection_protocol: 1.2.1
   xml: 6.5.0
+  standard_message_codec: 0.0.1+4
 
   _discoveryapis_commons: 1.0.6 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   async: 2.11.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
@@ -72,4 +73,4 @@ dev_dependencies:
   watcher: 1.1.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
   web_socket_channel: 2.4.0 # THIS LINE IS AUTOGENERATED - TO UPDATE USE "flutter update-packages --force-upgrade"
 
-# PUBSPEC CHECKSUM: 6040
+# PUBSPEC CHECKSUM: 70e2

dev/integration_tests/flavors/assets/common/common.txt

+this is a test asset not meant for any specific flavor
\ No newline at end of file

dev/integration_tests/flavors/assets/free/free.txt

+this is a test asset for --flavor free
\ No newline at end of file

dev/integration_tests/flavors/assets/paid/paid.txt

+this is a test asset for --flavor paid
\ No newline at end of file

dev/integration_tests/flavors/assets/premium/premium.txt

+premium
\ No newline at end of file

dev/integration_tests/flavors/pubspec.yaml

@@ -75,5 +75,13 @@ dev_dependencies:
 
 flutter:
   uses-material-design: true
+  assets:
+    - assets/common/common.txt
+    - path: assets/paid/
+      flavors:
+        - paid
+    - path: assets/free/
+      flavors:
+        - free
 
 # PUBSPEC CHECKSUM: 6bd3

packages/flutter_tools/bin/xcode_backend.dart

@@ -401,6 +401,7 @@ class Context {
       '-dTargetPlatform=ios',
       '-dTargetFile=$targetPath',
       '-dBuildMode=$buildMode',
+      if (environment['FLAVOR'] != null) '-dFlavor=${environment['FLAVOR']}',
       '-dIosArchs=${environment['ARCHS'] ?? ''}',
       '-dSdkRoot=${environment['SDKROOT'] ?? ''}',
       '-dSplitDebugInfo=${environment['SPLIT_DEBUG_INFO'] ?? ''}',

packages/flutter_tools/gradle/src/main/groovy/flutter.groovy

@@ -1057,6 +1057,7 @@ class FlutterPlugin implements Plugin<Project> {
             boolean isAndroidLibraryValue = isBuildingAar || isUsedAsSubproject
 
             String variantBuildMode = buildModeFor(variant.buildType)
+            String flavorValue = variant.getFlavorName()
             String taskName = toCamelCase(["compile", FLUTTER_BUILD_PREFIX, variant.name])
             // Be careful when configuring task below, Groovy has bizarre
             // scoping rules: writing `verbose isVerbose()` means calling
@@ -1094,6 +1095,7 @@ class FlutterPlugin implements Plugin<Project> {
                 deferredComponents deferredComponentsValue
                 validateDeferredComponents validateDeferredComponentsValue
                 isAndroidLibrary isAndroidLibraryValue
+                flavor flavorValue
             }
             File libJar = project.file("${project.buildDir}/$INTERMEDIATES_DIR/flutter/${variant.name}/libs.jar")
             Task packFlutterAppAotTask = project.tasks.create(name: "packLibs${FLUTTER_BUILD_PREFIX}${variant.name.capitalize()}", type: Jar) {
@@ -1380,6 +1382,8 @@ abstract class BaseFlutterTask extends DefaultTask {
     Boolean validateDeferredComponents
     @Optional @Input
     Boolean isAndroidLibrary
+    @Optional @Input
+    String flavor
 
     @OutputFiles
     FileCollection getDependenciesFiles() {
@@ -1460,6 +1464,9 @@ abstract class BaseFlutterTask extends DefaultTask {
             if (codeSizeDirectory != null) {
                 args "-dCodeSizeDirectory=${codeSizeDirectory}"
             }
+            if (flavor != null) {
+                args "-dFlavor=${flavor}"
+            }
             if (extraGenSnapshotOptions != null) {
                 args "--ExtraGenSnapshotOptions=${extraGenSnapshotOptions}"
             }

packages/flutter_tools/lib/src/base/deferred_component.dart

@@ -5,6 +5,7 @@
 import '../base/file_system.dart';
 import '../base/logger.dart';
 import '../convert.dart';
+import '../flutter_manifest.dart';
 
 /// Represents a configured deferred component as defined in
 /// the app's pubspec.yaml.
@@ -12,7 +13,7 @@ class DeferredComponent {
   DeferredComponent({
     required this.name,
     this.libraries = const <String>[],
-    this.assets = const <Uri>[],
+    this.assets = const <AssetsEntry>[],
   }) : _assigned = false;
 
   /// The name of the deferred component. There should be a matching
@@ -28,8 +29,8 @@ class DeferredComponent {
   /// libraries that are not listed here.
   final List<String> libraries;
 
-  /// Assets that are part of this component as a Uri relative to the project directory.
-  final List<Uri> assets;
+  /// Assets that are part of this component.
+  final List<AssetsEntry> assets;
 
   /// The minimal set of [LoadingUnit]s needed that contain all of the dart libraries in
   /// [libraries].
@@ -95,8 +96,11 @@ class DeferredComponent {
       }
     }
     out.write('\n  Assets:');
-    for (final Uri asset in assets) {
-      out.write('\n    - ${asset.path}');
+    for (final AssetsEntry asset in assets) {
+      out.write('\n    - ${asset.uri.path}');
+      if (asset.flavors.isNotEmpty) {
+        out.write(' (flavors: ${asset.flavors.join(', ')})');
+      }
     }
     return out.toString();
   }

packages/flutter_tools/lib/src/build_info.dart

@@ -286,6 +286,8 @@ class BuildInfo {
       'PACKAGE_CONFIG': packagesPath,
       if (codeSizeDirectory != null)
         'CODE_SIZE_DIRECTORY': codeSizeDirectory!,
+      if (flavor != null)
+        'FLAVOR': flavor!,
     };
   }
 
@@ -989,6 +991,9 @@ const String kBundleSkSLPath = 'BundleSkSLPath';
 /// The define to pass build name
 const String kBuildName = 'BuildName';
 
+/// The app flavor to build.
+const String kFlavor = 'Flavor';
+
 /// The define to pass build number
 const String kBuildNumber = 'BuildNumber';
 

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

@@ -46,6 +46,7 @@ abstract class AndroidAssetBundle extends Target {
     if (buildModeEnvironment == null) {
       throw MissingDefineException(kBuildMode, name);
     }
+
     final BuildMode buildMode = BuildMode.fromCliName(buildModeEnvironment);
     final Directory outputDirectory = environment.outputDir
       .childDirectory('flutter_assets')
@@ -68,6 +69,7 @@ abstract class AndroidAssetBundle extends Target {
       targetPlatform: TargetPlatform.android,
       buildMode: buildMode,
       shaderTarget: ShaderTarget.impellerAndroid,
+      flavor: environment.defines[kFlavor],
     );
     environment.depFileService.writeToFile(
       assetDepfile,

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

@@ -34,6 +34,7 @@ Future<Depfile> copyAssets(
   BuildMode? buildMode,
   required ShaderTarget shaderTarget,
   List<File> additionalInputs = const <File>[],
+  String? flavor,
 }) async {
   // Check for an SkSL bundle.
   final String? shaderBundlePath = environment.defines[kBundleSkSLPath] ?? environment.inputs[kBundleSkSLPath];
@@ -58,6 +59,7 @@ Future<Depfile> copyAssets(
     packagesPath: environment.projectDir.childFile('.packages').path,
     deferredComponentsEnabled: environment.defines[kDeferredComponents] == 'true',
     targetPlatform: targetPlatform,
+    flavor: flavor,
   );
   if (resultCode != 0) {
     throw Exception('Failed to bundle asset files.');
@@ -323,6 +325,7 @@ class CopyAssets extends Target {
       output,
       targetPlatform: TargetPlatform.android,
       shaderTarget: ShaderTarget.sksl,
+      flavor: environment.defines[kFlavor],
     );
     environment.depFileService.writeToFile(
       depfile,

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

@@ -58,6 +58,8 @@ class CopyFlutterBundle extends Target {
     if (buildModeEnvironment == null) {
       throw MissingDefineException(kBuildMode, 'copy_flutter_bundle');
     }
+    final String? flavor = environment.defines[kFlavor];
+
     final BuildMode buildMode = BuildMode.fromCliName(buildModeEnvironment);
     environment.outputDir.createSync(recursive: true);
 
@@ -78,6 +80,7 @@ class CopyFlutterBundle extends Target {
       targetPlatform: TargetPlatform.android,
       buildMode: buildMode,
       shaderTarget: ShaderTarget.sksl,
+      flavor: flavor,
     );
     environment.depFileService.writeToFile(
       assetDepfile,

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

@@ -533,6 +533,7 @@ abstract class IosAssetBundle extends Target {
         flutterProject.ios.infoPlist,
         flutterProject.ios.appFrameworkInfoPlist,
       ],
+      flavor: environment.defines[kFlavor],
     );
     environment.depFileService.writeToFile(
       assetDepfile,

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

@@ -393,6 +393,7 @@ abstract class MacOSBundleFlutterAssets extends Target {
     if (buildModeEnvironment == null) {
       throw MissingDefineException(kBuildMode, 'compile_macos_framework');
     }
+
     final BuildMode buildMode = BuildMode.fromCliName(buildModeEnvironment);
     final Directory frameworkRootDirectory = environment
         .outputDir
@@ -439,6 +440,7 @@ abstract class MacOSBundleFlutterAssets extends Target {
       assetDirectory,
       targetPlatform: TargetPlatform.darwin,
       shaderTarget: ShaderTarget.sksl,
+      flavor: environment.defines[kFlavor],
     );
     environment.depFileService.writeToFile(
       assetDepfile,

packages/flutter_tools/lib/src/bundle_builder.dart

@@ -114,6 +114,7 @@ Future<AssetBundle?> buildAssets({
   String? assetDirPath,
   String? packagesPath,
   TargetPlatform? targetPlatform,
+  String? flavor,
 }) async {
   assetDirPath ??= getAssetBuildDirectory();
   packagesPath ??= globals.fs.path.absolute('.packages');
@@ -124,6 +125,7 @@ Future<AssetBundle?> buildAssets({
     manifestPath: manifestPath,
     packagesPath: packagesPath,
     targetPlatform: targetPlatform,
+    flavor: flavor,
   );
   if (result != 0) {
     return null;

packages/flutter_tools/lib/src/flutter_manifest.dart

@@ -231,29 +231,12 @@ class FlutterManifest {
         _logger.printError('Expected deferred component manifest to be a map.');
         continue;
       }
-      List<Uri> assetsUri = <Uri>[];
-      final List<Object?>? assets = component['assets'] as List<Object?>?;
-      if (assets == null) {
-        assetsUri = const <Uri>[];
-      } else {
-        for (final Object? asset in assets) {
-          if (asset is! String || asset == '') {
-            _logger.printError('Deferred component asset manifest contains a null or empty uri.');
-            continue;
-          }
-          try {
-            assetsUri.add(Uri.parse(asset));
-          } on FormatException {
-            _logger.printError('Asset manifest contains invalid uri: $asset.');
-          }
-        }
-      }
       components.add(
         DeferredComponent(
           name: component['name'] as String,
           libraries: component['libraries'] == null ?
               <String>[] : (component['libraries'] as List<dynamic>).cast<String>(),
-          assets: assetsUri,
+          assets: _computeAssets(component['assets']),
         )
       );
     }
@@ -311,26 +294,7 @@ class FlutterManifest {
         : fontList.map<Map<String, Object?>?>(castStringKeyedMap).whereType<Map<String, Object?>>().toList();
   }
 
-  late final List<Uri> assets = _computeAssets();
-  List<Uri> _computeAssets() {
-    final List<Object?>? assets = _flutterDescriptor['assets'] as List<Object?>?;
-    if (assets == null) {
-      return const <Uri>[];
-    }
-    final List<Uri> results = <Uri>[];
-    for (final Object? asset in assets) {
-      if (asset is! String || asset == '') {
-        _logger.printError('Asset manifest contains a null or empty uri.');
-        continue;
-      }
-      try {
-        results.add(Uri(pathSegments: asset.split('/')));
-      } on FormatException {
-        _logger.printError('Asset manifest contains invalid uri: $asset.');
-      }
-    }
-    return results;
-  }
+  late final List<AssetsEntry> assets = _computeAssets(_flutterDescriptor['assets']);
 
   late final List<Font> fonts = _extractFonts();
 
@@ -521,15 +485,7 @@ void _validateFlutter(YamlMap? yaml, List<String> errors) {
           errors.add('Expected "$yamlKey" to be a bool, but got $yamlValue (${yamlValue.runtimeType}).');
         }
       case 'assets':
-        if (yamlValue is! YamlList) {
-          errors.add('Expected "$yamlKey" to be a list, but got $yamlValue (${yamlValue.runtimeType}).');
-        } else if (yamlValue.isEmpty) {
-          break;
-        } else if (yamlValue[0] is! String) {
-          errors.add(
-            'Expected "$yamlKey" to be a list of strings, but the first element is $yamlValue (${yamlValue.runtimeType}).',
-          );
-        }
+        errors.addAll(_validateAssets(yamlValue));
       case 'shaders':
         if (yamlValue is! YamlList) {
           errors.add('Expected "$yamlKey" to be a list, but got $yamlValue (${yamlValue.runtimeType}).');
@@ -640,17 +596,52 @@ void _validateDeferredComponents(MapEntry<Object?, Object?> kvp, List<String> er
         }
       }
       if (valueMap.containsKey('assets')) {
-        final Object? assets = valueMap['assets'];
-        if (assets is! YamlList) {
-          errors.add('Expected "assets" to be a list, but got $assets (${assets.runtimeType}).');
-        } else {
-          _validateListType<String>(assets, errors, '"assets" key in the $i element of "${kvp.key}"', 'file paths');
-        }
+        errors.addAll(_validateAssets(valueMap['assets']));
       }
     }
   }
 }
 
+List<String> _validateAssets(Object? yaml) {
+  final (_, List<String> errors) = _computeAssetsSafe(yaml);
+  return errors;
+}
+
+// TODO(andrewkolos): We end up parsing the assets section twice, once during
+// validation and once when the assets getter is called. We should consider
+// refactoring this class to parse and store everything in the constructor.
+// https://github.com/flutter/flutter/issues/139183
+(List<AssetsEntry>, List<String> errors) _computeAssetsSafe(Object? yaml) {
+  if (yaml == null) {
+    return (const <AssetsEntry>[], const <String>[]);
+  }
+  if (yaml is! YamlList) {
+    final String error = 'Expected "assets" to be a list, but got $yaml (${yaml.runtimeType}).';
+    return (const <AssetsEntry>[], <String>[error]);
+  }
+  final List<AssetsEntry> results = <AssetsEntry>[];
+  final List<String> errors = <String>[];
+  for (final Object? rawAssetEntry in yaml) {
+    final (AssetsEntry? parsed, String? error) = AssetsEntry.parseFromYamlSafe(rawAssetEntry);
+    if (parsed != null) {
+      results.add(parsed);
+    }
+    if (error != null) {
+      errors.add(error);
+    }
+  }
+  return (results, errors);
+}
+
+List<AssetsEntry> _computeAssets(Object? assetsSection) {
+  final (List<AssetsEntry> result, List<String> errors) = _computeAssetsSafe(assetsSection);
+  if (errors.isNotEmpty) {
+    throw Exception('Uncaught error(s) in assets section: '
+      '${errors.join('\n')}');
+  }
+  return result;
+}
+
 void _validateFonts(YamlList fonts, List<String> errors) {
   const Set<int> fontWeights = <int>{
     100, 200, 300, 400, 500, 600, 700, 800, 900,
@@ -703,3 +694,103 @@ void _validateFonts(YamlList fonts, List<String> errors) {
     }
   }
 }
+
+/// Represents an entry under the `assets` section of a pubspec.
+@immutable
+class AssetsEntry {
+  const AssetsEntry({
+    required this.uri,
+    this.flavors = const <String>[],
+  });
+
+  final Uri uri;
+  final List<String> flavors;
+
+  static const String _pathKey = 'path';
+  static const String _flavorKey = 'flavors';
+
+  static AssetsEntry? parseFromYaml(Object? yaml) {
+    final (AssetsEntry? value, String? error) = parseFromYamlSafe(yaml);
+    if (error != null) {
+      throw Exception('Unexpected error when parsing assets entry');
+    }
+    return value!;
+  }
+
+  static (AssetsEntry? assetsEntry, String? error) parseFromYamlSafe(Object? yaml) {
+
+    (Uri?, String?) tryParseUri(String uri) {
+      try {
+        return (Uri(pathSegments: uri.split('/')), null);
+      } on FormatException {
+        return (null, 'Asset manifest contains invalid uri: $uri.');
+      }
+    }
+
+    if (yaml == null || yaml == '') {
+      return (null, 'Asset manifest contains a null or empty uri.');
+    }
+
+    if (yaml is String) {
+      final (Uri? uri, String? error) = tryParseUri(yaml);
+      return uri == null ? (null, error) : (AssetsEntry(uri: uri), null);
+    }
+
+    if (yaml is Map) {
+      if (yaml.keys.isEmpty) {
+        return (null, null);
+      }
+
+      final Object? path = yaml[_pathKey];
+      final Object? flavors = yaml[_flavorKey];
+
+      if (path == null || path is! String) {
+        return (null, 'Asset manifest entry is malformed. '
+          'Expected asset entry to be either a string or a map '
+          'containing a "$_pathKey" entry. Got ${path.runtimeType} instead.');
+      }
+
+      final Uri uri = Uri(pathSegments: path.split('/'));
+
+      if (flavors == null) {
+        return (AssetsEntry(uri: uri), null);
+      }
+
+      if (flavors is! YamlList) {
+        return(null, 'Asset manifest entry is malformed. '
+          'Expected "$_flavorKey" entry to be a list of strings. '
+          'Got ${flavors.runtimeType} instead.');
+      }
+
+      final List<String> flavorsListErrors = <String>[];
+      _validateListType<String>(flavors, flavorsListErrors, 'flavors list of entry "$path"', 'String');
+      if (flavorsListErrors.isNotEmpty) {
+        return (null, 'Asset manifest entry is malformed. '
+          'Expected "$_flavorKey" entry to be a list of strings.\n'
+          '${flavorsListErrors.join('\n')}');
+      }
+
+      final AssetsEntry entry = AssetsEntry(
+        uri: Uri(pathSegments: path.split('/')),
+        flavors: List<String>.from(flavors),
+      );
+
+      return (entry, null);
+    }
+
+    return (null, 'Assets entry had unexpected shape. '
+      'Expected a string or an object. Got ${yaml.runtimeType} instead.');
+  }
+
+  @override
+  bool operator ==(Object other) {
+    if (other is! AssetsEntry) {
+      return false;
+    }
+
+    return uri == other.uri && flavors == other.flavors;
+  }
+
+  @override
+  int get hashCode => Object.hash(uri.hashCode, flavors.hashCode);
+}

packages/flutter_tools/lib/src/run_hot.dart

@@ -141,6 +141,8 @@ class HotRunner extends ResidentRunner {
 
   NativeAssetsBuildRunner? _buildRunner;
 
+  String? flavor;
+
   Future<void> _calculateTargetPlatform() async {
     if (_targetPlatform != null) {
       return;
@@ -494,7 +496,10 @@ class HotRunner extends ResidentRunner {
     final bool rebuildBundle = assetBundle.needsBuild();
     if (rebuildBundle) {
       globals.printTrace('Updating assets');
-      final int result = await assetBundle.build(packagesPath: '.packages');
+      final int result = await assetBundle.build(
+        packagesPath: '.packages',
+        flavor: debuggingOptions.buildInfo.flavor,
+      );
       if (result != 0) {
         return UpdateFSReport();
       }

packages/flutter_tools/test/commands.shard/hermetic/run_test.dart

@@ -1567,6 +1567,7 @@ class CapturingAppDomain extends AppDomain {
     bool machine = true,
     String? userIdentifier,
     bool enableDevTools = true,
+    String? flavor,
   }) async {
     this.multidexEnabled = multidexEnabled;
     this.userIdentifier = userIdentifier;

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

@@ -9,11 +9,15 @@ import 'package:file/memory.dart';
 import 'package:flutter_tools/src/artifacts.dart';
 import 'package:flutter_tools/src/asset.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/base/platform.dart';
+import 'package:flutter_tools/src/base/user_messages.dart';
 import 'package:flutter_tools/src/build_info.dart';
 import 'package:flutter_tools/src/bundle_builder.dart';
+import 'package:flutter_tools/src/cache.dart';
 import 'package:flutter_tools/src/devfs.dart';
 import 'package:flutter_tools/src/globals.dart' as globals;
+import 'package:flutter_tools/src/project.dart';
 import 'package:standard_message_codec/standard_message_codec.dart';
 
 import '../src/common.dart';
@@ -23,7 +27,9 @@ const String shaderLibDir = '/./shader_lib';
 
 void main() {
   group('AssetBundle.build', () {
+    late Logger logger;
     late FileSystem testFileSystem;
+    late Platform platform;
 
     setUp(() async {
       testFileSystem = MemoryFileSystem(
@@ -32,6 +38,8 @@ void main() {
           : FileSystemStyle.posix,
       );
       testFileSystem.currentDirectory = testFileSystem.systemTempDirectory.createTempSync('flutter_asset_bundle_test.');
+      logger = BufferLogger.test();
+      platform = FakePlatform(operatingSystem: globals.platform.operatingSystem);
     });
 
     testUsingContext('nonempty', () async {
@@ -323,6 +331,185 @@ flutter:
       FileSystem: () => testFileSystem,
       ProcessManager: () => FakeProcessManager.any(),
     });
+
+    group('flavors feature', () {
+      Future<ManifestAssetBundle> buildBundleWithFlavor(String? flavor) async {
+        final ManifestAssetBundle bundle = ManifestAssetBundle(
+          logger: logger,
+          fileSystem: testFileSystem,
+          platform: platform,
+          splitDeferredAssets: true,
+        );
+
+        await bundle.build(
+          packagesPath: '.packages',
+          flutterProject: FlutterProject.fromDirectoryTest(testFileSystem.currentDirectory),
+          flavor: flavor,
+        );
+        return bundle;
+      }
+
+      late final String? previousCacheFlutterRootValue;
+
+      setUpAll(() {
+        previousCacheFlutterRootValue = Cache.flutterRoot;
+        Cache.flutterRoot = Cache.defaultFlutterRoot(platform: platform, fileSystem: testFileSystem, userMessages: UserMessages());
+      });
+
+      tearDownAll(() => Cache.flutterRoot = previousCacheFlutterRootValue);
+
+      testWithoutContext('correctly bundles assets given a simple asset manifest with flavors', () async {
+        testFileSystem.file('.packages').createSync();
+        testFileSystem.file(testFileSystem.path.join('assets', 'common', 'image.png')).createSync(recursive: true);
+        testFileSystem.file(testFileSystem.path.join('assets', 'vanilla', 'ice-cream.png')).createSync(recursive: true);
+        testFileSystem.file(testFileSystem.path.join('assets', 'strawberry', 'ice-cream.png')).createSync(recursive: true);
+        testFileSystem.file(testFileSystem.path.join('assets', 'orange', 'ice-cream.png')).createSync(recursive: true);
+        testFileSystem.file('pubspec.yaml')
+          ..createSync()
+          ..writeAsStringSync(r'''
+name: example
+flutter:
+  assets:
+    - assets/common/
+    - path: assets/vanilla/
+      flavors:
+        - vanilla
+    - path: assets/strawberry/
+      flavors:
+        - strawberry
+    - path: assets/orange/ice-cream.png
+      flavors:
+        - orange
+  ''');
+
+        ManifestAssetBundle bundle;
+        bundle = await buildBundleWithFlavor(null);
+        expect(bundle.entries.keys, contains('assets/common/image.png'));
+        expect(bundle.entries.keys, isNot(contains('assets/vanilla/ice-cream.png')));
+        expect(bundle.entries.keys, isNot(contains('assets/strawberry/ice-cream.png')));
+        expect(bundle.entries.keys, isNot(contains('assets/orange/ice-cream.png')));
+
+        bundle = await buildBundleWithFlavor('strawberry');
+        expect(bundle.entries.keys, contains('assets/common/image.png'));
+        expect(bundle.entries.keys, isNot(contains('assets/vanilla/ice-cream.png')));
+        expect(bundle.entries.keys, contains('assets/strawberry/ice-cream.png'));
+        expect(bundle.entries.keys, isNot(contains('assets/orange/ice-cream.png')));
+
+        bundle = await buildBundleWithFlavor('orange');
+        expect(bundle.entries.keys, contains('assets/common/image.png'));
+        expect(bundle.entries.keys, isNot(contains('assets/vanilla/ice-cream.png')));
+        expect(bundle.entries.keys, isNot(contains('assets/strawberry/ice-cream.png')));
+        expect(bundle.entries.keys, contains('assets/orange/ice-cream.png'));
+      });
+
+      testWithoutContext('throws a tool exit when a non-flavored folder contains a flavored asset', () async {
+        testFileSystem.file('.packages').createSync();
+        testFileSystem.file(testFileSystem.path.join('assets', 'unflavored.png')).createSync(recursive: true);
+        testFileSystem.file(testFileSystem.path.join('assets', 'vanillaOrange.png')).createSync(recursive: true);
+
+        testFileSystem.file('pubspec.yaml')
+          ..createSync()
+          ..writeAsStringSync(r'''
+  name: example
+  flutter:
+    assets:
+      - assets/
+      - path: assets/vanillaOrange.png
+        flavors:
+          - vanilla
+          - orange
+  ''');
+
+        expect(
+          buildBundleWithFlavor(null),
+          throwsToolExit(message: 'Multiple assets entries include the file '
+            '"assets/vanillaOrange.png", but they specify different lists of flavors.\n'
+            'An entry with the path "assets/" does not specify any flavors.\n'
+            'An entry with the path "assets/vanillaOrange.png" specifies the flavor(s): "vanilla", "orange".\n\n'
+            'Consider organizing assets with different flavors into different directories.'),
+        );
+      });
+
+      testWithoutContext('throws a tool exit when a flavored folder contains a flavorless asset', () async {
+        testFileSystem.file('.packages').createSync();
+        testFileSystem.file(testFileSystem.path.join('vanilla', 'vanilla.png')).createSync(recursive: true);
+        testFileSystem.file(testFileSystem.path.join('vanilla', 'flavorless.png')).createSync(recursive: true);
+
+        testFileSystem.file('pubspec.yaml')
+          ..createSync()
+          ..writeAsStringSync(r'''
+  name: example
+  flutter:
+    assets:
+      - path: vanilla/
+        flavors:
+          - vanilla
+      - vanilla/flavorless.png
+  ''');
+        expect(
+          buildBundleWithFlavor(null),
+          throwsToolExit(message: 'Multiple assets entries include the file '
+            '"vanilla/flavorless.png", but they specify different lists of flavors.\n'
+            'An entry with the path "vanilla/" specifies the flavor(s): "vanilla".\n'
+            'An entry with the path "vanilla/flavorless.png" does not specify any flavors.\n\n'
+            'Consider organizing assets with different flavors into different directories.'),
+        );
+      });
+
+      testWithoutContext('tool exits when two file-explicit entries give the same asset different flavors', () {
+        testFileSystem.file('.packages').createSync();
+        testFileSystem.file('orange.png').createSync(recursive: true);
+        testFileSystem.file('pubspec.yaml')
+          ..createSync()
+          ..writeAsStringSync(r'''
+  name: example
+  flutter:
+    assets:
+      - path: orange.png
+        flavors:
+          - orange
+      - path: orange.png
+        flavors:
+          - mango
+  ''');
+
+        expect(
+          buildBundleWithFlavor(null),
+          throwsToolExit(message: 'Multiple assets entries include the file '
+            '"orange.png", but they specify different lists of flavors.\n'
+            'An entry with the path "orange.png" specifies the flavor(s): "orange".\n'
+            'An entry with the path "orange.png" specifies the flavor(s): "mango".'),
+        );
+    });
+
+      testWithoutContext('throws ToolExit when flavor from file-level declaration has different flavor from containing folder flavor declaration', () async {
+        testFileSystem.file('.packages').createSync();
+        testFileSystem.file(testFileSystem.path.join('vanilla', 'actually-strawberry.png')).createSync(recursive: true);
+        testFileSystem.file(testFileSystem.path.join('vanilla', 'vanilla.png')).createSync(recursive: true);
+
+        testFileSystem.file('pubspec.yaml')
+          ..createSync()
+          ..writeAsStringSync(r'''
+  name: example
+  flutter:
+    assets:
+      - path: vanilla/
+        flavors:
+          - vanilla
+      - path: vanilla/actually-strawberry.png
+        flavors:
+          - strawberry
+  ''');
+        expect(
+          buildBundleWithFlavor(null),
+          throwsToolExit(message: 'Multiple assets entries include the file '
+            '"vanilla/actually-strawberry.png", but they specify different lists of flavors.\n'
+            'An entry with the path "vanilla/" specifies the flavor(s): "vanilla".\n'
+            'An entry with the path "vanilla/actually-strawberry.png" '
+            'specifies the flavor(s): "strawberry".'),
+        );
+      });
+    });
   });
 
   group('AssetBundle.build (web builds)', () {

packages/flutter_tools/test/general.shard/base/deferred_component_test.dart

@@ -6,6 +6,7 @@ import 'package:file/memory.dart';
 import 'package:flutter_tools/src/base/deferred_component.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/logger.dart';
+import 'package:flutter_tools/src/flutter_manifest.dart';
 
 import '../../src/common.dart';
 
@@ -15,18 +16,27 @@ void main() {
       final DeferredComponent component = DeferredComponent(
         name: 'bestcomponent',
         libraries: <String>['lib1', 'lib2'],
-        assets: <Uri>[Uri.file('asset1'), Uri.file('asset2')],
+        assets: <AssetsEntry>[
+          AssetsEntry(uri: Uri.file('asset1')),
+          AssetsEntry(uri: Uri.file('asset2')),
+        ],
       );
       expect(component.name, 'bestcomponent');
       expect(component.libraries, <String>['lib1', 'lib2']);
-      expect(component.assets, <Uri>[Uri.file('asset1'), Uri.file('asset2')]);
+      expect(component.assets, <AssetsEntry>[
+          AssetsEntry(uri: Uri.file('asset1')),
+          AssetsEntry(uri: Uri.file('asset2')),
+      ]);
     });
 
     testWithoutContext('assignLoadingUnits selects the needed loading units and sets assigned', () {
       final DeferredComponent component = DeferredComponent(
         name: 'bestcomponent',
         libraries: <String>['lib1', 'lib2'],
-        assets: <Uri>[Uri.file('asset1'), Uri.file('asset2')],
+        assets: <AssetsEntry>[
+          AssetsEntry(uri: Uri.file('asset1')),
+          AssetsEntry(uri: Uri.file('asset2')),
+        ],
       );
       expect(component.libraries, <String>['lib1', 'lib2']);
       expect(component.assigned, false);
@@ -94,7 +104,10 @@ void main() {
       final DeferredComponent component = DeferredComponent(
         name: 'bestcomponent',
         libraries: <String>['lib1', 'lib2'],
-        assets: <Uri>[Uri.file('asset1'), Uri.file('asset2')],
+        assets: <AssetsEntry>[
+          AssetsEntry(uri: Uri.file('asset1')),
+          AssetsEntry(uri: Uri.file('asset2')),
+        ],
       );
       expect(component.toString(), '\nDeferredComponent: bestcomponent\n  Libraries:\n    - lib1\n    - lib2\n  Assets:\n    - asset1\n    - asset2');
     });
@@ -103,7 +116,10 @@ void main() {
       final DeferredComponent component = DeferredComponent(
         name: 'bestcomponent',
         libraries: <String>['lib1', 'lib2'],
-        assets: <Uri>[Uri.file('asset1'), Uri.file('asset2')],
+        assets: <AssetsEntry>[
+          AssetsEntry(uri: Uri.file('asset1')),
+          AssetsEntry(uri: Uri.file('asset2')),
+        ],
       );
       component.assignLoadingUnits(<LoadingUnit>[LoadingUnit(id: 2, libraries: <String>['lib1'])]);
       expect(component.toString(), '\nDeferredComponent: bestcomponent\n  Libraries:\n    - lib1\n    - lib2\n  LoadingUnits:\n    - 2\n  Assets:\n    - asset1\n    - asset2');

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

@@ -207,7 +207,7 @@ void main() {
   });
 
   testWithoutContext('toEnvironmentConfig encoding of standard values', () {
-    const BuildInfo buildInfo = BuildInfo(BuildMode.debug, '',
+    const BuildInfo buildInfo = BuildInfo(BuildMode.debug, 'strawberry',
       treeShakeIcons: true,
       trackWidgetCreation: true,
       dartDefines: <String>['foo=2', 'bar=2'],
@@ -220,7 +220,7 @@ void main() {
       packagesPath: 'foo/.dart_tool/package_config.json',
       codeSizeDirectory: 'foo/code-size',
       // These values are ignored by toEnvironmentConfig
-      androidProjectArgs: <String>['foo=bar', 'fizz=bazz']
+      androidProjectArgs: <String>['foo=bar', 'fizz=bazz'],
     );
 
     expect(buildInfo.toEnvironmentConfig(), <String, String>{
@@ -235,6 +235,7 @@ void main() {
       'BUNDLE_SKSL_PATH': 'foo/bar/baz.sksl.json',
       'PACKAGE_CONFIG': 'foo/.dart_tool/package_config.json',
       'CODE_SIZE_DIRECTORY': 'foo/code-size',
+      'FLAVOR': 'strawberry',
     });
   });
 

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

@@ -32,6 +32,7 @@ void main() {
       fileSystem: fileSystem,
       logger: BufferLogger.test(),
       platform: FakePlatform(),
+      defines: <String, String>{},
     );
     fileSystem.file(environment.buildDir.childFile('app.dill')).createSync(recursive: true);
     fileSystem.file('packages/flutter_tools/lib/src/build_system/targets/assets.dart')
@@ -93,6 +94,69 @@ flutter:
     ProcessManager: () => FakeProcessManager.any(),
   });
 
+  group("Only copies assets with a flavor if the assets' flavor matches the flavor in the environment", () {
+    testUsingContext('When the environment does not have a flavor defined', () async {
+      fileSystem.file('pubspec.yaml')
+        ..createSync()
+        ..writeAsStringSync('''
+  name: example
+  flutter:
+    assets:
+      - assets/common/
+      - path: assets/vanilla/
+        flavors:
+          - vanilla
+      - path: assets/strawberry/
+        flavors:
+          - strawberry
+  ''');
+
+      fileSystem.file('assets/common/image.png').createSync(recursive: true);
+      fileSystem.file('assets/vanilla/ice-cream.png').createSync(recursive: true);
+      fileSystem.file('assets/strawberry/ice-cream.png').createSync(recursive: true);
+
+      await const CopyAssets().build(environment);
+
+      expect(fileSystem.file('${environment.buildDir.path}/flutter_assets/assets/common/image.png'), exists);
+      expect(fileSystem.file('${environment.buildDir.path}/flutter_assets/assets/vanilla/ice-cream.png'), isNot(exists));
+      expect(fileSystem.file('${environment.buildDir.path}/flutter_assets/assets/strawberry/ice-cream.png'), isNot(exists));
+    }, overrides: <Type, Generator>{
+      FileSystem: () => fileSystem,
+      ProcessManager: () => FakeProcessManager.any(),
+    });
+
+    testUsingContext('When the environment has a flavor defined', () async {
+      environment.defines[kFlavor] = 'strawberry';
+      fileSystem.file('pubspec.yaml')
+        ..createSync()
+        ..writeAsStringSync('''
+  name: example
+  flutter:
+    assets:
+      - assets/common/
+      - path: assets/vanilla/
+        flavors:
+          - vanilla
+      - path: assets/strawberry/
+        flavors:
+          - strawberry
+  ''');
+
+      fileSystem.file('assets/common/image.png').createSync(recursive: true);
+      fileSystem.file('assets/vanilla/ice-cream.png').createSync(recursive: true);
+      fileSystem.file('assets/strawberry/ice-cream.png').createSync(recursive: true);
+
+      await const CopyAssets().build(environment);
+
+      expect(fileSystem.file('${environment.buildDir.path}/flutter_assets/assets/common/image.png'), exists);
+      expect(fileSystem.file('${environment.buildDir.path}/flutter_assets/assets/vanilla/ice-cream.png'), isNot(exists));
+      expect(fileSystem.file('${environment.buildDir.path}/flutter_assets/assets/strawberry/ice-cream.png'), exists);
+    }, overrides: <Type, Generator>{
+      FileSystem: () => fileSystem,
+      ProcessManager: () => FakeProcessManager.any(),
+    });
+  });
+
   testUsingContext('Throws exception if pubspec contains missing files', () async {
     fileSystem.file('pubspec.yaml')
       ..createSync()

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

@@ -733,7 +733,14 @@ class FakeBundle extends AssetBundle {
   List<File> get additionalDependencies => <File>[];
 
   @override
-  Future<int> build({String manifestPath = defaultManifestPath, String? assetDirPath, String? packagesPath, bool deferredComponentsEnabled = false, TargetPlatform? targetPlatform}) async {
+  Future<int> build({
+    String manifestPath = defaultManifestPath,
+    String? assetDirPath,
+    String? packagesPath,
+    bool deferredComponentsEnabled = false,
+    TargetPlatform? targetPlatform,
+    String? flavor,
+  }) async {
     return 0;
   }
 

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

@@ -160,6 +160,7 @@ void main() {
           'FRONTEND_SERVER_STARTER_PATH': frontendServerStarterPath,
           'INFOPLIST_PATH': 'Info.plist',
           'SDKROOT': sdkRoot,
+          'FLAVOR': 'strawberry',
           'SPLIT_DEBUG_INFO': splitDebugInfo,
           'TRACK_WIDGET_CREATION': trackWidgetCreation,
           'TREE_SHAKE_ICONS': treeShake,
@@ -174,6 +175,7 @@ void main() {
               '-dTargetPlatform=ios',
               '-dTargetFile=lib/main.dart',
               '-dBuildMode=${buildMode.toLowerCase()}',
+              '-dFlavor=strawberry',
               '-dIosArchs=$archs',
               '-dSdkRoot=$sdkRoot',
               '-dSplitDebugInfo=$splitDebugInfo',