Rearrange flutter assemble implementation (#36240)

packages/flutter_tools/lib/src/build_system/source.dart

@@ -65,8 +65,9 @@ class SourceVisitor {
             fs.path.split(environment.cacheDir.resolveSymbolicLinksSync()));
         break;
       case Environment.kFlutterRootDirectory:
+        // flutter root will not contain a symbolic link.
         segments.addAll(
-            fs.path.split(environment.cacheDir.resolveSymbolicLinksSync()));
+            fs.path.split(environment.flutterRootDir.absolute.path));
         break;
       default:
         throw InvalidPatternException(pattern);

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

@@ -10,10 +10,6 @@ import '../../devfs.dart';
 import '../build_system.dart';
 
 /// The copying logic for flutter assets.
-// TODO(jonahwilliams): combine the asset bundle logic with this rule so that
-// we can compute the key for deleted assets. This is required to remove assets
-// from build directories that are no longer part of the manifest and to unify
-// the update/diff logic.
 class AssetBehavior extends SourceBehavior {
   const AssetBehavior();
 
@@ -24,6 +20,8 @@ class AssetBehavior extends SourceBehavior {
       manifestPath: environment.projectDir.childFile('pubspec.yaml').path,
       packagesPath: environment.projectDir.childFile('.packages').path,
     );
+    // Filter the file type to remove the files that are generated by this
+    // command as inputs.
     final List<File> results = <File>[];
     final Iterable<DevFSFileContent> files = assetBundle.entries.values.whereType<DevFSFileContent>();
     for (DevFSFileContent devFsContent in files) {
@@ -40,16 +38,41 @@ class AssetBehavior extends SourceBehavior {
       packagesPath: environment.projectDir.childFile('.packages').path,
     );
     final List<File> results = <File>[];
-    for (MapEntry<String, DevFSContent> entry in assetBundle.entries.entries) {
-      final File file = fs.file(fs.path.join(environment.buildDir.path, 'flutter_assets', entry.key));
+    for (String key in assetBundle.entries.keys) {
+      final File file = fs.file(fs.path.join(environment.buildDir.path, 'flutter_assets', key));
       results.add(file);
     }
     return results;
   }
 }
 
-/// Copies the asset files from the [copyAssets] rule into place.
-Future<void> copyAssetsInvocation(Map<String, ChangeType> updates, Environment environment) async {
+/// Copy the assets defined in the flutter manifest into a build directory.
+class CopyAssets extends Target {
+  const CopyAssets();
+
+  @override
+  String get name => 'copy_assets';
+
+  @override
+  List<Target> get dependencies => const <Target>[];
+
+  @override
+  List<Source> get inputs => const <Source>[
+    Source.pattern('{FLUTTER_ROOT}/packages/flutter_tools/lib/src/build_system/targets/assets.dart'),
+    Source.pattern('{PROJECT_DIR}/pubspec.yaml'),
+    Source.behavior(AssetBehavior()),
+  ];
+
+  @override
+  List<Source> get outputs => const <Source>[
+    Source.pattern('{BUILD_DIR}/flutter_assets/AssetManifest.json'),
+    Source.pattern('{BUILD_DIR}/flutter_assets/FontManifest.json'),
+    Source.pattern('{BUILD_DIR}/flutter_assets/LICENSE'),
+    Source.behavior(AssetBehavior()), // <- everything in this subdirectory.
+  ];
+
+  @override
+  Future<void> build(List<File> inputFiles, Environment environment) async {
     final Directory output = environment
       .buildDir
       .childDirectory('flutter_assets');
@@ -75,21 +98,5 @@ Future<void> copyAssetsInvocation(Map<String, ChangeType> updates, Environment e
           resource.release();
         }
       }));
+  }
 }
-
-/// Copy the assets used in the application into a build directory.
-const Target copyAssets = Target(
-  name: 'copy_assets',
-  inputs: <Source>[
-    Source.pattern('{PROJECT_DIR}/pubspec.yaml'),
-    Source.behavior(AssetBehavior()),
-  ],
-  outputs: <Source>[
-    Source.pattern('{BUILD_DIR}/flutter_assets/AssetManifest.json'),
-    Source.pattern('{BUILD_DIR}/flutter_assets/FontManifest.json'),
-    Source.pattern('{BUILD_DIR}/flutter_assets/LICENSE'),
-    Source.behavior(AssetBehavior()), // <- everything in this subdirectory.
-  ],
-  dependencies: <Target>[],
-  buildAction: copyAssetsInvocation,
-);

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

@@ -2,42 +2,149 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import '../../artifacts.dart';
+import '../../base/build.dart';
+import '../../base/file_system.dart';
+import '../../base/io.dart';
+import '../../base/process_manager.dart';
+import '../../build_info.dart';
 import '../build_system.dart';
-import 'assets.dart';
+import '../exceptions.dart';
 import 'dart.dart';
 
-/// Create an iOS debug application.
-const Target debugIosApplication = Target(
-  name: 'debug_ios_application',
-  buildAction: null,
-  inputs: <Source>[],
-  outputs: <Source>[],
-  dependencies: <Target>[
-    copyAssets,
-    kernelSnapshot,
-  ]
-);
-
-/// Create an iOS profile application.
-const Target profileIosApplication = Target(
-  name: 'profile_ios_application',
-  buildAction: null,
-  inputs: <Source>[],
-  outputs: <Source>[],
-  dependencies: <Target>[
-    copyAssets,
-    aotAssemblyProfile,
-  ]
-);
-
-/// Create an iOS debug application.
-const Target releaseIosApplication = Target(
-  name: 'release_ios_application',
-  buildAction: null,
-  inputs: <Source>[],
-  outputs: <Source>[],
-  dependencies: <Target>[
-    copyAssets,
-    aotAssemblyRelease,
-  ]
-);
+/// Supports compiling a dart kernel file to an assembly file.
+///
+/// If more than one iOS arch is provided, then this rule will
+/// produce a univeral binary.
+abstract class AotAssemblyBase extends Target {
+  const AotAssemblyBase();
+
+  @override
+  Future<void> build(List<File> inputFiles, Environment environment) async {
+    final AOTSnapshotter snapshotter = AOTSnapshotter(reportTimings: false);
+    final String outputPath = environment.buildDir.path;
+    if (environment.defines[kBuildMode] == null) {
+      throw MissingDefineException(kBuildMode, 'aot_assembly');
+    }
+    if (environment.defines[kTargetPlatform] == null) {
+      throw MissingDefineException(kTargetPlatform, 'aot_assembly');
+    }
+    final bool bitcode = environment.defines[kBitcodeFlag] == 'true';
+    final BuildMode buildMode = getBuildModeForName(environment.defines[kBuildMode]);
+    final TargetPlatform targetPlatform = getTargetPlatformForName(environment.defines[kTargetPlatform]);
+    final List<IOSArch> iosArchs = environment.defines[kIosArchs]?.split(',')?.map(getIOSArchForName)?.toList()
+        ?? <IOSArch>[IOSArch.arm64];
+    if (targetPlatform != TargetPlatform.ios) {
+      throw Exception('aot_assembly is only supported for iOS applications');
+    }
+
+    // If we're building for a single architecture (common), then skip the lipo.
+    if (iosArchs.length == 1) {
+      final int snapshotExitCode = await snapshotter.build(
+        platform: targetPlatform,
+        buildMode: buildMode,
+        mainPath: environment.buildDir.childFile('app.dill').path,
+        packagesPath: environment.projectDir.childFile('.packages').path,
+        outputPath: outputPath,
+        iosArch: iosArchs.single,
+        bitcode: bitcode,
+      );
+      if (snapshotExitCode != 0) {
+        throw Exception('AOT snapshotter exited with code $snapshotExitCode');
+      }
+    } else {
+      // If we're building multiple iOS archs the binaries need to be lipo'd
+      // together.
+      final List<Future<int>> pending = <Future<int>>[];
+      for (IOSArch iosArch in iosArchs) {
+        pending.add(snapshotter.build(
+          platform: targetPlatform,
+          buildMode: buildMode,
+          mainPath: environment.buildDir.childFile('app.dill').path,
+          packagesPath: environment.projectDir.childFile('.packages').path,
+          outputPath: fs.path.join(outputPath, getNameForIOSArch(iosArch)),
+          iosArch: iosArch,
+          bitcode: bitcode,
+        ));
+      }
+      final List<int> results = await Future.wait(pending);
+      if (results.any((int result) => result != 0)) {
+        throw Exception('AOT snapshotter exited with code ${results.join()}');
+      }
+      final ProcessResult result = await processManager.run(<String>[
+        'lipo',
+        ...iosArchs.map((IOSArch iosArch) =>
+            fs.path.join(outputPath, getNameForIOSArch(iosArch), 'App.framework', 'App')),
+        '-create',
+        '-output',
+        fs.path.join(outputPath, 'App.framework', 'App'),
+      ]);
+      if (result.exitCode != 0) {
+        throw Exception('lipo exited with code ${result.exitCode}');
+      }
+    }
+  }
+}
+
+/// Generate an assembly target from a dart kernel file in release mode.
+class AotAssemblyRelease extends AotAssemblyBase {
+  const AotAssemblyRelease();
+
+  @override
+  String get name => 'aot_assembly_release';
+
+  @override
+  List<Source> get inputs => const <Source>[
+    Source.pattern('{FLUTTER_ROOT}/packages/flutter_tools/lib/src/build_system/targets/ios.dart'),
+    Source.pattern('{BUILD_DIR}/app.dill'),
+    Source.pattern('{PROJECT_DIR}/.packages'),
+    Source.artifact(Artifact.engineDartBinary),
+    Source.artifact(Artifact.skyEnginePath),
+    Source.artifact(Artifact.genSnapshot,
+      platform: TargetPlatform.ios,
+      mode: BuildMode.release,
+    ),
+  ];
+
+  @override
+  List<Source> get outputs => const <Source>[
+    Source.pattern('{BUILD_DIR}/App.framework/App'),
+  ];
+
+  @override
+  List<Target> get dependencies => const <Target>[
+    KernelSnapshot(),
+  ];
+}
+
+
+/// Generate an assembly target from a dart kernel file in profile mode.
+class AotAssemblyProfile extends AotAssemblyBase {
+  const AotAssemblyProfile();
+
+  @override
+  String get name => 'aot_assembly_profile';
+
+  @override
+  List<Source> get inputs => const <Source>[
+    Source.pattern('{FLUTTER_ROOT}/packages/flutter_tools/lib/src/build_system/targets/ios.dart'),
+    Source.pattern('{BUILD_DIR}/app.dill'),
+    Source.pattern('{PROJECT_DIR}/.packages'),
+    Source.artifact(Artifact.engineDartBinary),
+    Source.artifact(Artifact.skyEnginePath),
+    Source.artifact(Artifact.genSnapshot,
+      platform: TargetPlatform.ios,
+      mode: BuildMode.profile,
+    ),
+  ];
+
+  @override
+  List<Source> get outputs => const <Source>[
+    Source.pattern('{BUILD_DIR}/App.framework/App'),
+  ];
+
+  @override
+  List<Target> get dependencies => const <Target>[
+    KernelSnapshot(),
+  ];
+}

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

@@ -7,16 +7,45 @@ import '../../base/file_system.dart';
 import '../../globals.dart';
 import '../build_system.dart';
 
-// Copies all of the input files to the correct copy dir.
-Future<void> copyLinuxAssets(Map<String, ChangeType> updates,
-    Environment environment) async {
+/// Copies the Linux desktop embedding files to the copy directory.
+class UnpackLinux extends Target {
+  const UnpackLinux();
+
+  @override
+  String get name => 'unpack_linux';
+
+  @override
+  List<Source> get inputs => const <Source>[
+    Source.pattern('{FLUTTER_ROOT}/packages/flutter_tools/lib/src/build_system/targets/linux.dart'),
+    Source.artifact(Artifact.linuxDesktopPath),
+  ];
+
+  @override
+  List<Source> get outputs => const <Source>[
+    Source.pattern('{PROJECT_DIR}/linux/flutter/libflutter_linux.so'),
+    Source.pattern('{PROJECT_DIR}/linux/flutter/flutter_export.h'),
+    Source.pattern('{PROJECT_DIR}/linux/flutter/flutter_messenger.h'),
+    Source.pattern('{PROJECT_DIR}/linux/flutter/flutter_plugin_registrar.h'),
+    Source.pattern('{PROJECT_DIR}/linux/flutter/flutter_glfw.h'),
+    Source.pattern('{PROJECT_DIR}/linux/flutter/icudtl.dat'),
+    Source.pattern('{PROJECT_DIR}/linux/flutter/cpp_client_wrapper/*'),
+  ];
+
+  @override
+  List<Target> get dependencies => <Target>[];
+
+  @override
+  Future<void> build(List<File> inputFiles, Environment environment) async {
     final String basePath = artifacts.getArtifactPath(Artifact.linuxDesktopPath);
-  for (String input in updates.keys) {
+    for (File input in inputFiles) {
+      if (fs.path.basename(input.path) == 'linux.dart') {
+        continue;
+      }
       final String outputPath = fs.path.join(
         environment.projectDir.path,
         'linux',
         'flutter',
-      fs.path.relative(input, from: basePath),
+        fs.path.relative(input.path, from: basePath),
       );
       final File destinationFile = fs.file(outputPath);
       if (!destinationFile.parent.existsSync()) {
@@ -24,23 +53,5 @@ Future<void> copyLinuxAssets(Map<String, ChangeType> updates,
       }
       fs.file(input).copySync(destinationFile.path);
     }
+  }
 }
-
-/// Copies the Linux desktop embedding files to the copy directory.
-const Target unpackLinux = Target(
-  name: 'unpack_linux',
-  inputs: <Source>[
-    Source.artifact(Artifact.linuxDesktopPath),
-  ],
-  outputs: <Source>[
-    Source.pattern('{PROJECT_DIR}/linux/flutter/libflutter_linux.so'),
-    Source.pattern('{PROJECT_DIR}/linux/flutter/flutter_export.h'),
-    Source.pattern('{PROJECT_DIR}/linux/flutter/flutter_messenger.h'),
-    Source.pattern('{PROJECT_DIR}/linux/flutter/flutter_plugin_registrar.h'),
-    Source.pattern('{PROJECT_DIR}/linux/flutter/flutter_glfw.h'),
-    Source.pattern('{PROJECT_DIR}/linux/flutter/icudtl.dat'),
-    Source.pattern('{PROJECT_DIR}/linux/flutter/cpp_client_wrapper/*'),
-  ],
-  dependencies: <Target>[],
-  buildAction: copyLinuxAssets,
-);

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

@@ -8,8 +8,8 @@ import '../../base/io.dart';
 import '../../base/process_manager.dart';
 import '../../globals.dart';
 import '../build_system.dart';
-import 'assets.dart';
-import 'dart.dart';
+
+const String _kOutputPrefix = '{PROJECT_DIR}/macos/Flutter/FlutterMacOS.framework';
 
 /// Copy the macOS framework to the correct copy dir by invoking 'cp -R'.
 ///
@@ -19,37 +19,20 @@ import 'dart.dart';
 /// Removes any previous version of the framework that already exists in the
 /// target directory.
 // TODO(jonahwilliams): remove shell out.
-Future<void> copyFramework(Map<String, ChangeType> updates,
-    Environment environment) async {
-  final String basePath = artifacts.getArtifactPath(Artifact.flutterMacOSFramework);
-  final Directory targetDirectory = environment
-    .projectDir
-    .childDirectory('macos')
-    .childDirectory('Flutter')
-    .childDirectory('FlutterMacOS.framework');
-  if (targetDirectory.existsSync()) {
-    targetDirectory.deleteSync(recursive: true);
-  }
-
-  final ProcessResult result = processManager
-      .runSync(<String>['cp', '-R', basePath, targetDirectory.path]);
-  if (result.exitCode != 0) {
-    throw Exception(
-      'Failed to copy framework (exit ${result.exitCode}:\n'
-      '${result.stdout}\n---\n${result.stderr}',
-    );
-  }
-}
+class UnpackMacOS extends Target {
+  const UnpackMacOS();
 
-const String _kOutputPrefix = '{PROJECT_DIR}/macos/Flutter/FlutterMacOS.framework';
+  @override
+  String get name => 'unpack_macos';
 
-/// Copies the macOS desktop framework to the copy directory.
-const Target unpackMacos = Target(
-  name: 'unpack_macos',
-  inputs: <Source>[
+  @override
+  List<Source> get inputs => const <Source>[
+    Source.pattern('{FLUTTER_ROOT}/packages/flutter_tools/lib/src/build_system/targets/macos.dart'),
     Source.artifact(Artifact.flutterMacOSFramework),
-  ],
-  outputs: <Source>[
+  ];
+
+  @override
+  List<Source> get outputs => const <Source>[
     Source.pattern('$_kOutputPrefix/FlutterMacOS'),
     // Headers
     Source.pattern('$_kOutputPrefix/Headers/FLEOpenGLContextHandling.h'),
@@ -68,33 +51,30 @@ const Target unpackMacos = Target(
     Source.pattern('$_kOutputPrefix/Resources/icudtl.dat'),
     Source.pattern('$_kOutputPrefix/Resources/info.plist'),
     // Ignore Versions folder for now
-  ],
-  dependencies: <Target>[],
-  buildAction: copyFramework,
-);
+  ];
 
-/// Build a macOS application.
-const Target macosApplication = Target(
-  name: 'debug_macos_application',
-  buildAction: null,
-  inputs: <Source>[],
-  outputs: <Source>[],
-  dependencies: <Target>[
-    unpackMacos,
-    kernelSnapshot,
-    copyAssets,
-  ]
-);
+  @override
+  List<Target> get dependencies => <Target>[];
 
-/// Build a macOS release application.
-const Target macoReleaseApplication = Target(
-  name: 'release_macos_application',
-  buildAction: null,
-  inputs: <Source>[],
-  outputs: <Source>[],
-  dependencies: <Target>[
-    unpackMacos,
-    aotElfRelease,
-    copyAssets,
-  ]
-);
+  @override
+  Future<void> build(List<File> inputFiles, Environment environment) async {
+    final String basePath = artifacts.getArtifactPath(Artifact.flutterMacOSFramework);
+    final Directory targetDirectory = environment
+      .projectDir
+      .childDirectory('macos')
+      .childDirectory('Flutter')
+      .childDirectory('FlutterMacOS.framework');
+    if (targetDirectory.existsSync()) {
+      targetDirectory.deleteSync(recursive: true);
+    }
+
+    final ProcessResult result = await processManager
+        .run(<String>['cp', '-R', basePath, targetDirectory.path]);
+    if (result.exitCode != 0) {
+      throw Exception(
+        'Failed to copy framework (exit ${result.exitCode}:\n'
+        '${result.stdout}\n---\n${result.stderr}',
+      );
+    }
+  }
+}

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

@@ -7,17 +7,49 @@ import '../../base/file_system.dart';
 import '../../globals.dart';
 import '../build_system.dart';
 
-/// Copies all of the input files to the correct copy dir.
-Future<void> copyWindowsAssets(Map<String, ChangeType> updates,
-    Environment environment) async {
+/// Copies the Windows desktop embedding files to the copy directory.
+class UnpackWindows extends Target {
+  const UnpackWindows();
+
+  @override
+  String get name => 'unpack_windows';
+
+  @override
+  List<Source> get inputs => const <Source>[
+    Source.pattern('{FLUTTER_ROOT}/packages/flutter_tools/lib/src/build_system/targets/windows.dart'),
+    Source.artifact(Artifact.windowsDesktopPath),
+  ];
+
+  @override
+  List<Source> get outputs => const <Source>[
+    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_windows.dll'),
+    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_windows.dll.exp'),
+    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_windows.dll.lib'),
+    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_windows.dll.pdb'),
+    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_export.h'),
+    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_messenger.h'),
+    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_plugin_registrar.h'),
+    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_glfw.h'),
+    Source.pattern('{PROJECT_DIR}/windows/flutter/icudtl.dat'),
+    Source.pattern('{PROJECT_DIR}/windows/flutter/cpp_client_wrapper/*'),
+  ];
+
+  @override
+  List<Target> get dependencies => const <Target>[];
+
+  @override
+  Future<void> build(List<File> inputFiles, Environment environment) async {
     // This path needs to match the prefix in the rule below.
     final String basePath = artifacts.getArtifactPath(Artifact.windowsDesktopPath);
-  for (String input in updates.keys) {
+    for (File input in inputFiles) {
+      if (fs.path.basename(input.path) == 'windows.dart') {
+        continue;
+      }
       final String outputPath = fs.path.join(
         environment.projectDir.path,
         'windows',
         'flutter',
-      fs.path.relative(input, from: basePath),
+        fs.path.relative(input.path, from: basePath),
       );
       final File destinationFile = fs.file(outputPath);
       if (!destinationFile.parent.existsSync()) {
@@ -25,26 +57,5 @@ Future<void> copyWindowsAssets(Map<String, ChangeType> updates,
       }
       fs.file(input).copySync(destinationFile.path);
     }
+  }
 }
-
-/// Copies the Windows desktop embedding files to the copy directory.
-const Target unpackWindows = Target(
-  name: 'unpack_windows',
-  inputs: <Source>[
-    Source.artifact(Artifact.windowsDesktopPath),
-  ],
-  outputs: <Source>[
-    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_windows.dll'),
-    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_windows.dll.exp'),
-    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_windows.dll.lib'),
-    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_windows.dll.pdb'),
-    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_export.h'),
-    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_messenger.h'),
-    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_plugin_registrar.h'),
-    Source.pattern('{PROJECT_DIR}/windows/flutter/flutter_glfw.h'),
-    Source.pattern('{PROJECT_DIR}/windows/flutter/icudtl.dat'),
-    Source.pattern('{PROJECT_DIR}/windows/flutter/cpp_client_wrapper/*'),
-  ],
-  dependencies: <Target>[],
-  buildAction: copyWindowsAssets,
-);

packages/flutter_tools/lib/src/commands/assemble.dart

@@ -4,9 +4,13 @@
 
 import '../base/common.dart';
 import '../base/context.dart';
-import '../build_info.dart';
 import '../build_system/build_system.dart';
-import '../convert.dart';
+import '../build_system/targets/assets.dart';
+import '../build_system/targets/dart.dart';
+import '../build_system/targets/ios.dart';
+import '../build_system/targets/linux.dart';
+import '../build_system/targets/macos.dart';
+import '../build_system/targets/windows.dart';
 import '../globals.dart';
 import '../project.dart';
 import '../runner/flutter_command.dart';
@@ -14,30 +18,23 @@ import '../runner/flutter_command.dart';
 /// The [BuildSystem] instance.
 BuildSystem get buildSystem => context.get<BuildSystem>();
 
+/// All currently implemented targets.
+const List<Target> _kDefaultTargets = <Target>[
+  UnpackMacOS(),
+  UnpackLinux(),
+  UnpackWindows(),
+  CopyAssets(),
+  KernelSnapshot(),
+  AotElfProfile(),
+  AotElfRelease(),
+  AotAssemblyProfile(),
+  AotAssemblyRelease(),
+];
+
 /// Assemble provides a low level API to interact with the flutter tool build
 /// system.
 class AssembleCommand extends FlutterCommand {
   AssembleCommand() {
-    addSubcommand(AssembleRun());
-    addSubcommand(AssembleDescribe());
-    addSubcommand(AssembleListInputs());
-    addSubcommand(AssembleBuildDirectory());
-  }
-  @override
-  String get description => 'Assemble and build flutter resources.';
-
-  @override
-  String get name => 'assemble';
-
-
-  @override
-  Future<FlutterCommandResult> runCommand() {
-    return null;
-  }
-}
-
-abstract class AssembleBase extends FlutterCommand {
-  AssembleBase() {
     argParser.addMultiOption(
       'define',
       abbr: 'd',
@@ -57,36 +54,19 @@ abstract class AssembleBase extends FlutterCommand {
     );
   }
 
-  /// Returns the provided target platform.
-  ///
-  /// Throws a [ToolExit] if none is provided. This intentionally has no
-  /// default.
-  TargetPlatform get targetPlatform {
-    final String value = argResults['target-platform'] ?? 'darwin-x64';
-    if (value == null) {
-      throwToolExit('--target-platform is required for flutter assemble.');
-    }
-    return getTargetPlatformForName(value);
-  }
+  @override
+  String get description => 'Assemble and build flutter resources.';
 
-  /// Returns the provided build mode.
-  ///
-  /// Throws a [ToolExit] if none is provided. This intentionally has no
-  /// default.
-  BuildMode get buildMode {
-    final String value = argResults['build-mode'] ?? 'debug';
-    if (value == null) {
-      throwToolExit('--build-mode is required for flutter assemble.');
-    }
-    return getBuildModeForName(value);
-  }
+  @override
+  String get name => 'assemble';
 
-  /// The name of the target we are describing or building.
-  String get targetName {
+  /// The target we are building.
+  Target get target {
     if (argResults.rest.isEmpty) {
       throwToolExit('missing target name for flutter assemble.');
     }
-    return argResults.rest.first;
+    final String name = argResults.rest.first;
+    return _kDefaultTargets.firstWhere((Target target) => target.name == name);
   }
 
   /// The environmental configuration for a build invocation.
@@ -115,19 +95,10 @@ abstract class AssembleBase extends FlutterCommand {
     }
     return results;
   }
-}
-
-/// Execute a build starting from a target action.
-class AssembleRun extends AssembleBase {
-  @override
-  String get description => 'Execute the stages for a specified target.';
-
-  @override
-  String get name => 'run';
 
   @override
   Future<FlutterCommandResult> runCommand() async {
-    final BuildResult result = await buildSystem.build(targetName, environment, BuildSystemConfig(
+    final BuildResult result = await buildSystem.build(target, environment, buildSystemConfig: BuildSystemConfig(
       resourcePoolSize: argResults['resource-pool-size'],
     ));
     if (!result.success) {
@@ -142,67 +113,3 @@ class AssembleRun extends AssembleBase {
     return null;
   }
 }
-
-/// Fully describe a target and its dependencies.
-class AssembleDescribe extends AssembleBase {
-  @override
-  String get description => 'List the stages for a specified target.';
-
-  @override
-  String get name => 'describe';
-
-  @override
-  Future<FlutterCommandResult> runCommand() {
-    try {
-      printStatus(
-        json.encode(buildSystem.describe(targetName, environment))
-      );
-    } on Exception catch (err, stackTrace) {
-      printTrace(stackTrace.toString());
-      throwToolExit(err.toString());
-    }
-    return null;
-  }
-}
-
-/// List input files for a target.
-class AssembleListInputs extends AssembleBase {
-  @override
-  String get description => 'List the inputs for a particular target.';
-
-  @override
-  String get name => 'inputs';
-
-  @override
-  Future<FlutterCommandResult> runCommand() {
-    try {
-      final List<Map<String, Object>> results = buildSystem.describe(targetName, environment);
-      for (Map<String, Object> result in results) {
-        if (result['name'] == targetName) {
-          final List<String> inputs = result['inputs'];
-          inputs.forEach(printStatus);
-        }
-      }
-    } on Exception catch (err, stackTrace) {
-      printTrace(stackTrace.toString());
-      throwToolExit(err.toString());
-    }
-    return null;
-  }
-}
-
-/// Return the build directory for a configuiration.
-class AssembleBuildDirectory extends AssembleBase {
-  @override
-  String get description => 'List the inputs for a particular target.';
-
-  @override
-  String get name => 'build-dir';
-
-  @override
-  Future<FlutterCommandResult> runCommand() {
-    printStatus(environment.buildDir.path);
-    return null;
-  }
-}
-

packages/flutter_tools/lib/src/context_runner.dart

@@ -69,7 +69,7 @@ Future<T> runInContext<T>(
       Artifacts: () => CachedArtifacts(),
       AssetBundleFactory: () => AssetBundleFactory.defaultInstance,
       BotDetector: () => const BotDetector(),
-      BuildSystem: () => BuildSystem(),
+      BuildSystem: () => const BuildSystem(),
       Cache: () => Cache(),
       ChromeLauncher: () => const ChromeLauncher(),
       CocoaPods: () => CocoaPods(),

packages/flutter_tools/test/general.shard/build_system/exceptions_test.dart

@@ -12,19 +12,9 @@ void main() {
   test('Exceptions', () {
     final MissingInputException missingInputException = MissingInputException(
         <File>[fs.file('foo'), fs.file('bar')], 'example');
-    final CycleException cycleException = CycleException(const <Target>{
-      Target(
-        name: 'foo',
-        buildAction: null,
-        inputs: <Source>[],
-        outputs: <Source>[],
-      ),
-      Target(
-        name: 'bar',
-        buildAction: null,
-        inputs: <Source>[],
-        outputs: <Source>[],
-      )
+    final CycleException cycleException = CycleException(<Target>{
+      TestTarget()..name = 'foo',
+      TestTarget()..name = 'bar',
     });
     final InvalidPatternException invalidPatternException = InvalidPatternException(
       'ABC'
@@ -70,3 +60,24 @@ void main() {
     );
   });
 }
+
+class TestTarget extends Target {
+  TestTarget([this._build]);
+
+  final Future<void> Function(List<File> inputFiles, Environment environment) _build;
+
+  @override
+  Future<void> build(List<File> inputFiles, Environment environment) => _build(inputFiles, environment);
+
+  @override
+  List<Target> dependencies = <Target>[];
+
+  @override
+  List<Source> inputs = <Source>[];
+
+  @override
+  String name = 'test';
+
+  @override
+  List<Source> outputs = <Source>[];
+}

packages/flutter_tools/test/general.shard/build_system/filecache_test.dart

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/build_system/build_system.dart';
+import 'package:flutter_tools/src/build_system/file_hash_store.dart';
+import 'package:flutter_tools/src/build_system/filecache.pb.dart' as pb;
+
+import '../../src/common.dart';
+import '../../src/testbed.dart';
+
+void main() {
+  Testbed testbed;
+  Environment environment;
+
+  setUp(() {
+    testbed = Testbed(setup: () {
+      fs.directory('build').createSync();
+      environment = Environment(
+        projectDir: fs.currentDirectory,
+      );
+    });
+  });
+
+  test('Initializes file cache', () => testbed.run(() {
+    final FileHashStore fileCache = FileHashStore(environment);
+    fileCache.initialize();
+    fileCache.persist();
+
+    expect(fs.file(fs.path.join('build', '.filecache')).existsSync(), true);
+
+    final List<int> buffer = fs.file(fs.path.join('build', '.filecache')).readAsBytesSync();
+    final pb.FileStorage fileStorage = pb.FileStorage.fromBuffer(buffer);
+
+    expect(fileStorage.files, isEmpty);
+    expect(fileStorage.version, 1);
+  }));
+
+  test('saves and restores to file cache', () => testbed.run(() {
+    final File file = fs.file('foo.dart')
+      ..createSync()
+      ..writeAsStringSync('hello');
+    final FileHashStore fileCache = FileHashStore(environment);
+    fileCache.initialize();
+    fileCache.hashFiles(<File>[file]);
+    fileCache.persist();
+    final String currentHash =  fileCache.currentHashes[file.resolveSymbolicLinksSync()];
+    final List<int> buffer = fs.file(fs.path.join('build', '.filecache')).readAsBytesSync();
+    pb.FileStorage fileStorage = pb.FileStorage.fromBuffer(buffer);
+
+    expect(fileStorage.files.single.hash, currentHash);
+    expect(fileStorage.files.single.path, file.resolveSymbolicLinksSync());
+
+
+    final FileHashStore newFileCache = FileHashStore(environment);
+    newFileCache.initialize();
+    expect(newFileCache.currentHashes, isEmpty);
+    expect(newFileCache.previousHashes[fs.path.absolute('foo.dart')],  currentHash);
+    newFileCache.persist();
+
+    // Still persisted correctly.
+    fileStorage = pb.FileStorage.fromBuffer(buffer);
+
+    expect(fileStorage.files.single.hash, currentHash);
+    expect(fileStorage.files.single.path, file.resolveSymbolicLinksSync());
+  }));
+}

packages/flutter_tools/test/general.shard/build_system/source_test.dart

+// Copyright 2019 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:flutter_tools/src/artifacts.dart';
+import 'package:flutter_tools/src/base/file_system.dart';
+import 'package:flutter_tools/src/build_info.dart';
+import 'package:flutter_tools/src/build_system/build_system.dart';
+import 'package:flutter_tools/src/build_system/exceptions.dart';
+import 'package:flutter_tools/src/build_system/source.dart';
+import 'package:flutter_tools/src/cache.dart';
+
+import '../../src/common.dart';
+import '../../src/testbed.dart';
+
+void main() {
+  Testbed testbed;
+  SourceVisitor visitor;
+  Environment environment;
+
+  setUp(() {
+    testbed = Testbed(setup: () {
+      fs.directory('cache').createSync();
+      environment = Environment(
+        projectDir: fs.currentDirectory,
+        buildDir: fs.directory('build'),
+      );
+      visitor = SourceVisitor(environment);
+      environment.buildDir.createSync(recursive: true);
+    });
+  });
+
+  test('configures implicit vs explict correctly', () => testbed.run(() {
+    expect(const Source.pattern('{PROJECT_DIR}/foo').implicit, false);
+    expect(const Source.pattern('{PROJECT_DIR}/*foo').implicit, true);
+    expect(Source.function((Environment environment) => <File>[]).implicit, true);
+    expect(Source.behavior(TestBehavior()).implicit, true);
+  }));
+
+  test('can substitute {PROJECT_DIR}/foo', () => testbed.run(() {
+    fs.file('foo').createSync();
+    const Source fooSource = Source.pattern('{PROJECT_DIR}/foo');
+    fooSource.accept(visitor);
+
+    expect(visitor.sources.single.path, fs.path.absolute('foo'));
+  }));
+
+  test('can substitute {BUILD_DIR}/bar', () => testbed.run(() {
+    final String path = fs.path.join(environment.buildDir.path, 'bar');
+    fs.file(path).createSync();
+    const Source barSource = Source.pattern('{BUILD_DIR}/bar');
+    barSource.accept(visitor);
+
+    expect(visitor.sources.single.path, fs.path.absolute(path));
+  }));
+
+  test('can substitute {FLUTTER_ROOT}/foo', () => testbed.run(() {
+    final String path = fs.path.join(environment.flutterRootDir.path, 'foo');
+    fs.file(path).createSync();
+    const Source barSource = Source.pattern('{FLUTTER_ROOT}/foo');
+    barSource.accept(visitor);
+
+    expect(visitor.sources.single.path, fs.path.absolute(path));
+  }));
+
+  test('can substitute Artifact', () => testbed.run(() {
+    final String path = fs.path.join(
+      Cache.instance.getArtifactDirectory('engine').path,
+      'windows-x64',
+      'foo',
+    );
+    fs.file(path).createSync(recursive: true);
+    const Source fizzSource = Source.artifact(Artifact.windowsDesktopPath, platform: TargetPlatform.windows_x64);
+    fizzSource.accept(visitor);
+
+    expect(visitor.sources.single.resolveSymbolicLinksSync(), fs.path.absolute(path));
+  }));
+
+  test('can substitute {PROJECT_DIR}/*.fizz', () => testbed.run(() {
+    const Source fizzSource = Source.pattern('{PROJECT_DIR}/*.fizz');
+    fizzSource.accept(visitor);
+
+    expect(visitor.sources, isEmpty);
+
+    fs.file('foo.fizz').createSync();
+    fs.file('foofizz').createSync();
+
+
+    fizzSource.accept(visitor);
+
+    expect(visitor.sources.single.path, fs.path.absolute('foo.fizz'));
+  }));
+
+  test('can substitute {PROJECT_DIR}/fizz.*', () => testbed.run(() {
+    const Source fizzSource = Source.pattern('{PROJECT_DIR}/fizz.*');
+    fizzSource.accept(visitor);
+
+    expect(visitor.sources, isEmpty);
+
+    fs.file('fizz.foo').createSync();
+    fs.file('fizz').createSync();
+
+    fizzSource.accept(visitor);
+
+    expect(visitor.sources.single.path, fs.path.absolute('fizz.foo'));
+  }));
+
+
+  test('can substitute {PROJECT_DIR}/a*bc', () => testbed.run(() {
+    const Source fizzSource = Source.pattern('{PROJECT_DIR}/bc*bc');
+    fizzSource.accept(visitor);
+
+    expect(visitor.sources, isEmpty);
+
+    fs.file('bcbc').createSync();
+    fs.file('bc').createSync();
+
+    fizzSource.accept(visitor);
+
+    expect(visitor.sources.single.path, fs.path.absolute('bcbc'));
+  }));
+
+
+  test('crashes on bad substitute of two **', () => testbed.run(() {
+    const Source fizzSource = Source.pattern('{PROJECT_DIR}/*.*bar');
+
+    fs.file('abcd.bar').createSync();
+
+    expect(() => fizzSource.accept(visitor), throwsA(isInstanceOf<InvalidPatternException>()));
+  }));
+
+
+  test('can\'t substitute foo', () => testbed.run(() {
+    const Source invalidBase = Source.pattern('foo');
+
+    expect(() => invalidBase.accept(visitor), throwsA(isInstanceOf<InvalidPatternException>()));
+  }));
+}
+
+class TestBehavior extends SourceBehavior {
+  @override
+  List<File> inputs(Environment environment) {
+    return null;
+  }
+
+  @override
+  List<File> outputs(Environment environment) {
+    return null;
+  }
+}

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

@@ -10,19 +10,18 @@ import '../../../src/common.dart';
 import '../../../src/testbed.dart';
 
 void main() {
-  group('copy_assets', () {
-    Testbed testbed;
-    BuildSystem buildSystem;
+  const BuildSystem buildSystem = BuildSystem();
   Environment environment;
+  Testbed testbed;
 
   setUp(() {
     testbed = Testbed(setup: () {
       environment = Environment(
         projectDir: fs.currentDirectory,
       );
-        buildSystem = BuildSystem(<String, Target>{
-          copyAssets.name: copyAssets,
-        });
+      fs.file(fs.path.join('packages', 'flutter_tools', 'lib', 'src',
+          'build_system', 'targets', 'assets.dart'))
+        ..createSync(recursive: true);
       fs.file(fs.path.join('assets', 'foo', 'bar.png'))
         ..createSync(recursive: true);
       fs.file('.packages')
@@ -40,7 +39,7 @@ flutter:
   });
 
   test('Copies files to correct asset directory', () => testbed.run(() async {
-      await buildSystem.build('copy_assets', environment, const BuildSystemConfig());
+    await buildSystem.build(const CopyAssets(), environment);
 
     expect(fs.file(fs.path.join(environment.buildDir.path, 'flutter_assets', 'AssetManifest.json')).existsSync(), true);
     expect(fs.file(fs.path.join(environment.buildDir.path, 'flutter_assets', 'FontManifest.json')).existsSync(), true);
@@ -50,7 +49,7 @@ flutter:
   }));
 
   test('Does not leave stale files in build directory', () => testbed.run(() async {
-      await buildSystem.build('copy_assets', environment, const BuildSystemConfig());
+    await buildSystem.build(const CopyAssets(), environment);
 
     expect(fs.file(fs.path.join(environment.buildDir.path, 'flutter_assets', 'assets/foo/bar.png')).existsSync(), true);
     // Modify manifest to remove asset.
@@ -61,10 +60,9 @@ name: example
 
 flutter:
 ''');
-      await buildSystem.build('copy_assets', environment, const BuildSystemConfig());
+    await buildSystem.build(const CopyAssets(), environment);
 
     // See https://github.com/flutter/flutter/issues/35293
     expect(fs.file(fs.path.join(environment.buildDir.path, 'flutter_assets', 'assets/foo/bar.png')).existsSync(), false);
   }));
-  });
 }

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

@@ -10,6 +10,7 @@ import 'package:flutter_tools/src/build_info.dart';
 import 'package:flutter_tools/src/build_system/build_system.dart';
 import 'package:flutter_tools/src/build_system/exceptions.dart';
 import 'package:flutter_tools/src/build_system/targets/dart.dart';
+import 'package:flutter_tools/src/build_system/targets/ios.dart';
 import 'package:flutter_tools/src/cache.dart';
 import 'package:flutter_tools/src/compile.dart';
 import 'package:flutter_tools/src/macos/xcode.dart';
@@ -22,9 +23,8 @@ import '../../../src/mocks.dart';
 import '../../../src/testbed.dart';
 
 void main() {
-  group('dart rules', () {
+  const BuildSystem buildSystem = BuildSystem();
   Testbed testbed;
-    BuildSystem buildSystem;
   Environment androidEnvironment;
   Environment iosEnvironment;
   MockProcessManager mockProcessManager;
@@ -35,8 +35,8 @@ void main() {
   });
 
   setUp(() {
-      mockProcessManager = MockProcessManager();
     mockXcode = MockXcode();
+    mockProcessManager = MockProcessManager();
     testbed = Testbed(setup: () {
       androidEnvironment = Environment(
         projectDir: fs.currentDirectory,
@@ -52,7 +52,6 @@ void main() {
           kTargetPlatform: getNameForTargetPlatform(TargetPlatform.ios),
         }
       );
-        buildSystem = BuildSystem();
       HostPlatform hostPlatform;
       if (platform.isWindows) {
         hostPlatform = HostPlatform.windows_x64;
@@ -90,6 +89,8 @@ flutter_tools:lib/''');
         fs.path.join('lib', 'foo.dart'),
         fs.path.join('lib', 'bar.dart'),
         fs.path.join('lib', 'fizz'),
+        fs.path.join('packages', 'flutter_tools', 'lib', 'src', 'build_system', 'targets', 'dart.dart'),
+        fs.path.join('packages', 'flutter_tools', 'lib', 'src', 'build_system', 'targets', 'ios.dart'),
       ];
       for (String path in paths) {
         fs.file(path).createSync(recursive: true);
@@ -101,62 +102,79 @@ flutter_tools:lib/''');
   });
 
   test('kernel_snapshot Produces correct output directory', () => testbed.run(() async {
-      await buildSystem.build('kernel_snapshot', androidEnvironment, const BuildSystemConfig());
+    await buildSystem.build(const KernelSnapshot(), androidEnvironment);
 
-      expect(fs.file(fs.path.join(androidEnvironment.buildDir.path,'main.app.dill')).existsSync(), true);
+    expect(fs.file(fs.path.join(androidEnvironment.buildDir.path,'app.dill')).existsSync(), true);
   }));
 
   test('kernel_snapshot throws error if missing build mode', () => testbed.run(() async {
-      final BuildResult result = await buildSystem.build('kernel_snapshot',
-          androidEnvironment..defines.remove(kBuildMode), const BuildSystemConfig());
+    final BuildResult result = await buildSystem.build(const KernelSnapshot(),
+        androidEnvironment..defines.remove(kBuildMode));
 
     expect(result.exceptions.values.single.exception, isInstanceOf<MissingDefineException>());
   }));
 
   test('aot_elf_profile Produces correct output directory', () => testbed.run(() async {
-      await buildSystem.build('aot_elf_profile', androidEnvironment, const BuildSystemConfig());
+    await buildSystem.build(const AotElfProfile(), androidEnvironment);
 
-      expect(fs.file(fs.path.join(androidEnvironment.buildDir.path, 'main.app.dill')).existsSync(), true);
+    expect(fs.file(fs.path.join(androidEnvironment.buildDir.path, 'app.dill')).existsSync(), true);
     expect(fs.file(fs.path.join(androidEnvironment.buildDir.path, 'app.so')).existsSync(), true);
   }));
 
   test('aot_elf_profile throws error if missing build mode', () => testbed.run(() async {
-      final BuildResult result = await buildSystem.build('aot_elf_profile',
-          androidEnvironment..defines.remove(kBuildMode), const BuildSystemConfig());
+    final BuildResult result = await buildSystem.build(const AotElfProfile(),
+        androidEnvironment..defines.remove(kBuildMode));
 
     expect(result.exceptions.values.single.exception, isInstanceOf<MissingDefineException>());
   }));
 
 
   test('aot_elf_profile throws error if missing target platform', () => testbed.run(() async {
-      final BuildResult result = await buildSystem.build('aot_elf_profile',
-          androidEnvironment..defines.remove(kTargetPlatform), const BuildSystemConfig());
+    final BuildResult result = await buildSystem.build(const AotElfProfile(),
+        androidEnvironment..defines.remove(kTargetPlatform));
 
     expect(result.exceptions.values.single.exception, isInstanceOf<MissingDefineException>());
   }));
 
 
   test('aot_assembly_profile throws error if missing build mode', () => testbed.run(() async {
-      final BuildResult result = await buildSystem.build('aot_assembly_profile',
-          iosEnvironment..defines.remove(kBuildMode), const BuildSystemConfig());
+    final BuildResult result = await buildSystem.build(const AotAssemblyProfile(),
+        iosEnvironment..defines.remove(kBuildMode));
 
     expect(result.exceptions.values.single.exception, isInstanceOf<MissingDefineException>());
   }));
 
   test('aot_assembly_profile throws error if missing target platform', () => testbed.run(() async {
-      final BuildResult result = await buildSystem.build('aot_assembly_profile',
-          iosEnvironment..defines.remove(kTargetPlatform), const BuildSystemConfig());
+    final BuildResult result = await buildSystem.build(const AotAssemblyProfile(),
+        iosEnvironment..defines.remove(kTargetPlatform));
 
     expect(result.exceptions.values.single.exception, isInstanceOf<MissingDefineException>());
   }));
 
   test('aot_assembly_profile throws error if built for non-iOS platform', () => testbed.run(() async {
-      final BuildResult result = await buildSystem.build('aot_assembly_profile',
-          androidEnvironment, const BuildSystemConfig());
+    final BuildResult result = await buildSystem
+        .build(const AotAssemblyProfile(), androidEnvironment);
 
     expect(result.exceptions.values.single.exception, isInstanceOf<Exception>());
   }));
 
+  test('aot_assembly_profile will lipo binaries together when multiple archs are requested', () => testbed.run(() async {
+    iosEnvironment.defines[kIosArchs] ='armv7,arm64';
+    when(mockProcessManager.run(any)).thenAnswer((Invocation invocation) async {
+      fs.file(fs.path.join(iosEnvironment.buildDir.path, 'App.framework', 'App'))
+          .createSync(recursive: true);
+      return FakeProcessResult(
+        stdout: '',
+        stderr: '',
+      );
+    });
+    final BuildResult result = await buildSystem
+        .build(const AotAssemblyProfile(), iosEnvironment);
+    expect(result.success, true);
+  }, overrides: <Type, Generator>{
+    ProcessManager: () => mockProcessManager,
+  }));
+
   test('aot_assembly_profile with bitcode sends correct argument to snapshotter (one arch)', () => testbed.run(() async {
     iosEnvironment.defines[kIosArchs] = 'arm64';
     iosEnvironment.defines[kBitcodeFlag] = 'true';
@@ -176,8 +194,7 @@ flutter_tools:lib/''');
     when(mockXcode.clang(any)).thenAnswer((_) => Future<RunResult>.value(fakeRunResult));
     when(mockXcode.dsymutil(any)).thenAnswer((_) => Future<RunResult>.value(fakeRunResult));
 
-      final BuildResult result = await buildSystem.build('aot_assembly_profile',
-          iosEnvironment, const BuildSystemConfig());
+    final BuildResult result = await buildSystem.build(const AotAssemblyProfile(), iosEnvironment);
 
     expect(result.success, true);
     verify(mockXcode.cc(argThat(contains('-fembed-bitcode')))).called(1);
@@ -207,8 +224,7 @@ flutter_tools:lib/''');
     when(mockXcode.clang(any)).thenAnswer((_) => Future<RunResult>.value(fakeRunResult));
     when(mockXcode.dsymutil(any)).thenAnswer((_) => Future<RunResult>.value(fakeRunResult));
 
-      final BuildResult result = await buildSystem.build('aot_assembly_profile',
-          iosEnvironment, const BuildSystemConfig());
+    final BuildResult result = await buildSystem.build(const AotAssemblyProfile(), iosEnvironment);
 
     expect(result.success, true);
     verify(mockXcode.cc(argThat(contains('-fembed-bitcode')))).called(2);
@@ -229,14 +245,12 @@ flutter_tools:lib/''');
         stderr: '',
       );
     });
-      final BuildResult result = await buildSystem.build('aot_assembly_profile',
-          iosEnvironment, const BuildSystemConfig());
+    final BuildResult result = await buildSystem.build(const AotAssemblyProfile(), iosEnvironment);
 
     expect(result.success, true);
   }, overrides: <Type, Generator>{
     ProcessManager: () => mockProcessManager,
   }));
-  });
 }
 
 class MockProcessManager extends Mock implements ProcessManager {}

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

@@ -13,14 +13,14 @@ import '../../../src/common.dart';
 import '../../../src/testbed.dart';
 
 void main() {
-  group('unpack_linux', () {
   Testbed testbed;
-    BuildSystem buildSystem;
+  const BuildSystem buildSystem = BuildSystem();
   Environment environment;
   MockPlatform mockPlatform;
 
   setUpAll(() {
     Cache.disableLocking();
+    Cache.flutterRoot = '';
   });
 
   setUp(() {
@@ -33,9 +33,6 @@ void main() {
       environment = Environment(
         projectDir: fs.currentDirectory,
       );
-        buildSystem = BuildSystem(<String, Target>{
-          unpackLinux.name: unpackLinux,
-        });
       fs.file('bin/cache/artifacts/engine/linux-x64/libflutter_linux.so').createSync(recursive: true);
       fs.file('bin/cache/artifacts/engine/linux-x64/flutter_export.h').createSync();
       fs.file('bin/cache/artifacts/engine/linux-x64/flutter_messenger.h').createSync();
@@ -43,6 +40,7 @@ void main() {
       fs.file('bin/cache/artifacts/engine/linux-x64/flutter_glfw.h').createSync();
       fs.file('bin/cache/artifacts/engine/linux-x64/icudtl.dat').createSync();
       fs.file('bin/cache/artifacts/engine/linux-x64/cpp_client_wrapper/foo').createSync(recursive: true);
+      fs.file('packages/flutter_tools/lib/src/build_system/targets/linux.dart').createSync(recursive: true);
       fs.directory('linux').createSync();
     }, overrides: <Type, Generator>{
       Platform: () => mockPlatform,
@@ -50,7 +48,7 @@ void main() {
   });
 
   test('Copies files to correct cache directory', () => testbed.run(() async {
-      final BuildResult result = await buildSystem.build('unpack_linux', environment, const BuildSystemConfig());
+    final BuildResult result = await buildSystem.build(const UnpackLinux(), environment);
 
     expect(result.hasException, false);
     expect(fs.file('linux/flutter/libflutter_linux.so').existsSync(), true);
@@ -63,22 +61,24 @@ void main() {
   }));
 
   test('Does not re-copy files unecessarily', () => testbed.run(() async {
-      await buildSystem.build('unpack_linux', environment, const BuildSystemConfig());
-      final DateTime modified = fs.file('linux/flutter/libflutter_linux.so').statSync().modified;
-      await buildSystem.build('unpack_linux', environment, const BuildSystemConfig());
+    await buildSystem.build(const UnpackLinux(), environment);
+    // Set a date in the far distant past to deal with the limited resolution
+    // of the windows filesystem.
+    final DateTime theDistantPast = DateTime(1991, 8, 23);
+    fs.file('linux/flutter/libflutter_linux.so').setLastModifiedSync(theDistantPast);
+    await buildSystem.build(const UnpackLinux(), environment);
 
-      expect(fs.file('linux/flutter/libflutter_linux.so').statSync().modified, equals(modified));
+    expect(fs.file('linux/flutter/libflutter_linux.so').statSync().modified, equals(theDistantPast));
   }));
 
   test('Detects changes in input cache files', () => testbed.run(() async {
-      await buildSystem.build('unpack_linux', environment, const BuildSystemConfig());
+    await buildSystem.build(const UnpackLinux(), environment);
     fs.file('bin/cache/artifacts/engine/linux-x64/libflutter_linux.so').writeAsStringSync('asd'); // modify cache.
 
-      await buildSystem.build('unpack_linux', environment, const BuildSystemConfig());
+    await buildSystem.build(const UnpackLinux(), environment);
 
     expect(fs.file('linux/flutter/libflutter_linux.so').readAsStringSync(), 'asd');
   }));
-  });
 }
 
 class MockPlatform extends Mock implements Platform {}

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

@@ -8,6 +8,7 @@ import 'package:flutter_tools/src/base/platform.dart';
 import 'package:flutter_tools/src/base/process_manager.dart';
 import 'package:flutter_tools/src/build_system/build_system.dart';
 import 'package:flutter_tools/src/build_system/targets/macos.dart';
+import 'package:flutter_tools/src/cache.dart';
 import 'package:mockito/mockito.dart';
 import 'package:process/process.dart';
 
@@ -15,12 +16,16 @@ import '../../../src/common.dart';
 import '../../../src/testbed.dart';
 
 void main() {
-  group('unpack_macos', () {
   Testbed testbed;
-    BuildSystem buildSystem;
+  const BuildSystem buildSystem = BuildSystem();
   Environment environment;
   MockPlatform mockPlatform;
 
+  setUpAll(() {
+    Cache.disableLocking();
+    Cache.flutterRoot = '';
+  });
+
   setUp(() {
     mockPlatform = MockPlatform();
     when(mockPlatform.isWindows).thenReturn(false);
@@ -30,9 +35,6 @@ void main() {
       environment = Environment(
         projectDir: fs.currentDirectory,
       );
-        buildSystem = BuildSystem(<String, Target>{
-          unpackMacos.name: unpackMacos,
-        });
       final List<File> inputs = <File>[
         fs.file('bin/cache/artifacts/engine/darwin-x64/FlutterMacOS.framework/FlutterMacOS'),
         fs.file('bin/cache/artifacts/engine/darwin-x64/FlutterMacOS.framework/Headers/FLEOpenGLContextHandling.h'),
@@ -48,11 +50,12 @@ void main() {
         fs.file('bin/cache/artifacts/engine/darwin-x64/FlutterMacOS.framework/Modules/module.modulemap'),
         fs.file('bin/cache/artifacts/engine/darwin-x64/FlutterMacOS.framework/Resources/icudtl.dat'),
         fs.file('bin/cache/artifacts/engine/darwin-x64/FlutterMacOS.framework/Resources/info.plist'),
+        fs.file('packages/flutter_tools/lib/src/build_system/targets/macos.dart'),
       ];
       for (File input in inputs) {
         input.createSync(recursive: true);
       }
-        when(processManager.runSync(any)).thenAnswer((Invocation invocation) {
+      when(processManager.run(any)).thenAnswer((Invocation invocation) async {
         final List<String> arguments = invocation.positionalArguments.first;
         final Directory source = fs.directory(arguments[arguments.length - 2]);
         final Directory target = fs.directory(arguments.last)
@@ -76,7 +79,7 @@ void main() {
   });
 
   test('Copies files to correct cache directory', () => testbed.run(() async {
-      await buildSystem.build('unpack_macos', environment, const BuildSystemConfig());
+    await buildSystem.build(const UnpackMacOS(), environment);
 
     expect(fs.directory('macos/Flutter/FlutterMacOS.framework').existsSync(), true);
     expect(fs.file('macos/Flutter/FlutterMacOS.framework/FlutterMacOS').existsSync(), true);
@@ -94,7 +97,6 @@ void main() {
     expect(fs.file('macos/Flutter/FlutterMacOS.framework/Resources/icudtl.dat').existsSync(), true);
     expect(fs.file('macos/Flutter/FlutterMacOS.framework/Resources/info.plist').existsSync(), true);
   }));
-  });
 }
 
 class MockPlatform extends Mock implements Platform {}

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

@@ -14,18 +14,17 @@ import '../../../src/common.dart';
 import '../../../src/testbed.dart';
 
 void main() {
-  group('unpack_windows', () {
   Testbed testbed;
-    BuildSystem buildSystem;
+  const BuildSystem buildSystem = BuildSystem();
   Environment environment;
   Platform platform;
 
   setUpAll(() {
     Cache.disableLocking();
+    Cache.flutterRoot = '';
   });
 
   setUp(() {
-      Cache.flutterRoot = '';
     platform = MockPlatform();
     when(platform.isWindows).thenReturn(true);
     when(platform.isMacOS).thenReturn(false);
@@ -35,9 +34,6 @@ void main() {
       environment = Environment(
         projectDir: fs.currentDirectory,
       );
-        buildSystem = BuildSystem(<String, Target>{
-          unpackWindows.name: unpackWindows,
-        });
       fs.file(r'C:\bin\cache\artifacts\engine\windows-x64\flutter_export.h').createSync(recursive: true);
       fs.file(r'C:\bin\cache\artifacts\engine\windows-x64\flutter_messenger.h').createSync();
       fs.file(r'C:\bin\cache\artifacts\engine\windows-x64\flutter_windows.dll').createSync();
@@ -50,6 +46,7 @@ void main() {
       fs.file(r'C:\bin\cache\artifacts\engine\windows-x64\flutter_glfw.h').createSync();
       fs.file(r'C:\bin\cache\artifacts\engine\windows-x64\icudtl.dat').createSync();
       fs.file(r'C:\bin\cache\artifacts\engine\windows-x64\cpp_client_wrapper\foo').createSync(recursive: true);
+      fs.file(r'C:\packages\flutter_tools\lib\src\build_system\targets\windows.dart').createSync(recursive: true);
       fs.directory('windows').createSync();
     }, overrides: <Type, Generator>{
       FileSystem: () => MemoryFileSystem(style: FileSystemStyle.windows),
@@ -58,7 +55,7 @@ void main() {
   });
 
   test('Copies files to correct cache directory', () => testbed.run(() async {
-      await buildSystem.build('unpack_windows', environment, const BuildSystemConfig());
+    await buildSystem.build(const UnpackWindows(), environment);
 
     expect(fs.file(r'C:\windows\flutter\flutter_export.h').existsSync(), true);
     expect(fs.file(r'C:\windows\flutter\flutter_messenger.h').existsSync(), true);
@@ -75,23 +72,29 @@ void main() {
   }));
 
   test('Does not re-copy files unecessarily', () => testbed.run(() async {
-      await buildSystem.build('unpack_windows', environment, const BuildSystemConfig());
-      final DateTime modified = fs.file(r'C:\windows\flutter\flutter_export.h').statSync().modified;
-      await buildSystem.build('unpack_windows', environment, const BuildSystemConfig());
+    await buildSystem.build(const UnpackWindows(), environment);
+    // Set a date in the far distant past to deal with the limited resolution
+    // of the windows filesystem.
+    final DateTime theDistantPast = DateTime(1991, 8, 23);
+    fs.file(r'C:\windows\flutter\flutter_export.h').setLastModifiedSync(theDistantPast);
+    await buildSystem.build(const UnpackWindows(), environment);
 
-      expect(fs.file(r'C:\windows\flutter\flutter_export.h').statSync().modified, equals(modified));
+    expect(fs.file(r'C:\windows\flutter\flutter_export.h').statSync().modified, equals(theDistantPast));
   }));
 
   test('Detects changes in input cache files', () => testbed.run(() async {
-      await buildSystem.build('unpack_windows', environment, const BuildSystemConfig());
+    await buildSystem.build(const UnpackWindows(), environment);
+    // Set a date in the far distant past to deal with the limited resolution
+    // of the windows filesystem.
+    final DateTime theDistantPast = DateTime(1991, 8, 23);
+    fs.file(r'C:\windows\flutter\flutter_export.h').setLastModifiedSync(theDistantPast);
     final DateTime modified = fs.file(r'C:\windows\flutter\flutter_export.h').statSync().modified;
     fs.file(r'C:\bin\cache\artifacts\engine\windows-x64\flutter_export.h').writeAsStringSync('asd'); // modify cache.
 
-      await buildSystem.build('unpack_windows', environment, const BuildSystemConfig());
+    await buildSystem.build(const UnpackWindows(), environment);
 
     expect(fs.file(r'C:\windows\flutter\flutter_export.h').statSync().modified, isNot(modified));
-    }), skip: true); // TODO(jonahwilliams): track down flakiness.
-  });
+  }));
 }
 
 class MockPlatform extends Mock implements Platform {}

packages/flutter_tools/test/general.shard/commands/assemble_test.dart

@@ -3,7 +3,6 @@
 // found in the LICENSE file.
 
 import 'package:args/command_runner.dart';
-import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/logger.dart';
 import 'package:flutter_tools/src/build_system/build_system.dart';
 import 'package:flutter_tools/src/cache.dart';
@@ -15,7 +14,6 @@ import '../../src/common.dart';
 import '../../src/testbed.dart';
 
 void main() {
-  group('Assemble', () {
   Testbed testbed;
   MockBuildSystem mockBuildSystem;
 
@@ -30,53 +28,17 @@ void main() {
     });
   });
 
-    test('Can list the output directory relative to project root', () => testbed.run(() async {
-      final CommandRunner<void> commandRunner = createTestCommandRunner(AssembleCommand());
-      await commandRunner.run(<String>['assemble', '--flutter-root=.', 'build-dir', '-dBuildMode=debug']);
-      final BufferLogger bufferLogger = logger;
-      final Environment environment = Environment(
-        defines: <String, String>{
-          'BuildMode': 'debug'
-        }, projectDir: fs.currentDirectory,
-        buildDir: fs.directory(fs.path.join('.dart_tool', 'flutter_build')).absolute,
-      );
-
-      expect(bufferLogger.statusText.trim(), environment.buildDir.path);
-    }));
-
-    test('Can describe a target', () => testbed.run(() async {
-      when(mockBuildSystem.describe('foobar', any)).thenReturn(<Map<String, Object>>[
-        <String, Object>{'fizz': 'bar'},
-      ]);
-      final CommandRunner<void> commandRunner = createTestCommandRunner(AssembleCommand());
-      await commandRunner.run(<String>['assemble', '--flutter-root=.', 'describe', 'foobar']);
-      final BufferLogger bufferLogger = logger;
-
-      expect(bufferLogger.statusText.trim(), '[{"fizz":"bar"}]');
-    }));
-
-    test('Can describe a target\'s inputs', () => testbed.run(() async {
-      when(mockBuildSystem.describe('foobar', any)).thenReturn(<Map<String, Object>>[
-        <String, Object>{'name': 'foobar', 'inputs': <String>['bar', 'baz']},
-      ]);
-      final CommandRunner<void> commandRunner = createTestCommandRunner(AssembleCommand());
-      await commandRunner.run(<String>['assemble', '--flutter-root=.', 'inputs', 'foobar']);
-      final BufferLogger bufferLogger = logger;
-
-      expect(bufferLogger.statusText.trim(), 'bar\nbaz');
-    }));
-
   test('Can run a build', () => testbed.run(() async {
-      when(mockBuildSystem.build('foobar', any, any)).thenAnswer((Invocation invocation) async {
+    when(mockBuildSystem.build(any, any, buildSystemConfig: anyNamed('buildSystemConfig')))
+        .thenAnswer((Invocation invocation) async {
       return BuildResult(true, const <String, ExceptionMeasurement>{}, const <String, PerformanceMeasurement>{});
     });
     final CommandRunner<void> commandRunner = createTestCommandRunner(AssembleCommand());
-      await commandRunner.run(<String>['assemble', 'run', 'foobar']);
+    await commandRunner.run(<String>['assemble', 'unpack_macos']);
     final BufferLogger bufferLogger = logger;
 
     expect(bufferLogger.statusText.trim(), 'build succeeded');
   }));
-  });
 }
 
 class MockBuildSystem extends Mock implements BuildSystem {}