Revert "It's time to #deleteDart1 (#18293)" (#18313)

Several benchmarks started failing during kernel compile:
1. Timeouts:
   * commands_test
   * hot_mode_dev_cycle__benchmark
   * run_machine_concurrent_hot_reload
   * service_extensions_test

2. Kernel compiler crash:
   * hot_mode_dev_cycle_linux__benchmark
   * routing_test

3. Unexpected termination:
   * hot_mode_dev_cycle_win__benchmark

This reverts commit ed63e708.

dev/bots/test.dart

@@ -68,8 +68,12 @@ Future<Null> _generateDocs() async {
 }
 
 Future<Null> _verifyInternationalizations() async {
-  final EvalResult genResult = await _evalCommand(dart,
-    <String>[ '--preview-dart-2', path.join('dev', 'tools', 'gen_localizations.dart'), ],
+  final EvalResult genResult = await _evalCommand(
+    dart,
+    <String>[
+      '--preview-dart-2',
+      path.join('dev', 'tools', 'gen_localizations.dart'),
+    ],
     workingDirectory: flutterRoot,
   );
 

dev/devicelab/bin/tasks/gradle_plugin_test.dart

@@ -32,6 +32,14 @@ void main() async {
         return new TaskResult.failure(errorMessage);
       }
 
+      section('gradlew assembleDebug no-preview-dart-2');
+      await project.runGradleTask('assembleDebug', options: <String>['-Ppreview-dart-2=false']);
+      errorMessage = _validateSnapshotDependency(project,
+          '${project.rootPath}/build/app/intermediates/flutter/debug/snapshot_blob.bin');
+      if (errorMessage != null) {
+        return new TaskResult.failure(errorMessage);
+      }
+
       section('gradlew assembleProfile');
       await project.runGradleTask('assembleProfile');
 

dev/devicelab/bin/tasks/hot_mode_dev_cycle__benchmark_dart1.dart

+// Copyright (c) 2017 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 'dart:async';
+
+import 'package:flutter_devicelab/tasks/hot_mode_tests.dart';
+import 'package:flutter_devicelab/framework/framework.dart';
+
+Future<Null> main() async {
+  await task(createHotModeTest(isPreviewDart2: false));
+}

dev/devicelab/bin/tasks/hot_mode_dev_cycle_ios__benchmark_dart1.dart

+// Copyright (c) 2018 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 'dart:async';
+
+import 'package:flutter_devicelab/tasks/hot_mode_tests.dart';
+import 'package:flutter_devicelab/framework/framework.dart';
+import 'package:flutter_devicelab/framework/adb.dart';
+
+Future<Null> main() async {
+  deviceOperatingSystem = DeviceOperatingSystem.ios;
+  await task(createHotModeTest(isPreviewDart2: false));
+}

dev/devicelab/lib/tasks/hot_mode_tests.dart

@@ -16,7 +16,7 @@ import '../framework/utils.dart';
 final Directory _editedFlutterGalleryDir = dir(path.join(Directory.systemTemp.path, 'edited_flutter_gallery'));
 final Directory flutterGalleryDir = dir(path.join(flutterDirectory.path, 'examples/flutter_gallery'));
 
-TaskFunction createHotModeTest() {
+TaskFunction createHotModeTest({ bool isPreviewDart2 = true }) {
   return () async {
     final Device device = await devices.workingDevice;
     await device.unlock();
@@ -25,6 +25,10 @@ TaskFunction createHotModeTest() {
     final List<String> options = <String>[
       '--hot', '-d', device.deviceId, '--benchmark', '--verbose', '--resident'
     ];
+    if (isPreviewDart2)
+      options.add('--preview-dart-2');
+    else
+      options.add('--no-preview-dart-2');
     setLocalEngineOptionIfNecessary(options);
     int hotReloadCount = 0;
     Map<String, dynamic> twoReloadsData;
@@ -88,8 +92,8 @@ TaskFunction createHotModeTest() {
         }
         benchmarkFile.deleteSync();
 
-        // start `flutter run` again to make sure it loads from the previous
-        // state; frontend loads up from previously generated kernel files.
+        // start `flutter run` again to make sure it loads from the previous state
+        // (in case of --preview-dart-2 frontend loads up from previously generated kernel files).
         {
           final Process process = await startProcess(
               path.join(flutterDirectory.path, 'bin', 'flutter'),

dev/devicelab/lib/tasks/microbenchmarks.dart

@@ -23,7 +23,7 @@ TaskFunction createMicrobenchmarkTask() {
     final Device device = await devices.workingDevice;
     await device.unlock();
 
-    Future<Map<String, double>> _runMicrobench(String benchmarkPath) async {
+    Future<Map<String, double>> _runMicrobench(String benchmarkPath, {bool previewDart2 = true}) async {
       Future<Map<String, double>> _run() async {
         print('Running $benchmarkPath');
         final Directory appDir = dir(
@@ -38,6 +38,10 @@ TaskFunction createMicrobenchmarkTask() {
             '-d',
             device.deviceId,
           ];
+          if (previewDart2)
+            options.add('--preview-dart-2');
+          else
+            options.add('--no-preview-dart-2');
           setLocalEngineOptionIfNecessary(options);
           options.add(benchmarkPath);
           return await _startFlutter(
@@ -57,6 +61,26 @@ TaskFunction createMicrobenchmarkTask() {
     allResults.addAll(await _runMicrobench('lib/gestures/velocity_tracker_bench.dart'));
     allResults.addAll(await _runMicrobench('lib/stocks/animation_bench.dart'));
 
+    // Run micro-benchmarks once again in --no-preview-dart-2 mode.
+    // Append "_dart1" suffix to the result keys to distinguish them from
+    // the original results.
+
+    void addDart1Results(Map<String, double> benchmarkResults) {
+      benchmarkResults.forEach((String key, double result) {
+        allResults[key + '_dart1'] = result;
+      });
+    }
+
+    addDart1Results(await _runMicrobench(
+        'lib/stocks/layout_bench.dart', previewDart2: false));
+    addDart1Results(await _runMicrobench(
+        'lib/stocks/layout_bench.dart', previewDart2: false));
+    addDart1Results(await _runMicrobench(
+        'lib/stocks/build_bench.dart', previewDart2: false));
+    addDart1Results(await _runMicrobench(
+        'lib/gestures/velocity_tracker_bench.dart', previewDart2: false));
+    addDart1Results(await _runMicrobench(
+        'lib/stocks/animation_bench.dart', previewDart2: false));
     return new TaskResult.success(allResults, benchmarkScoreKeys: allResults.keys.toList());
   };
 }

dev/devicelab/lib/tasks/perf_tests.dart

@@ -205,13 +205,23 @@ class CompileTest {
       final Map<String, dynamic> metrics = <String, dynamic>{}
         ..addAll(await _compileAot())
         ..addAll(await _compileApp())
-        ..addAll(await _compileDebug());
+        ..addAll(await _compileDebug())
+        ..addAll(_suffix(await _compileAot(previewDart2: false), '__dart1'))
+        ..addAll(_suffix(await _compileApp(previewDart2: false), '__dart1'))
+        ..addAll(_suffix(await _compileDebug(previewDart2: false), '__dart1'));
 
       return new TaskResult.success(metrics, benchmarkScoreKeys: metrics.keys.toList());
     });
   }
 
-  static Future<Map<String, dynamic>> _compileAot() async {
+  static Map<String, dynamic> _suffix(Map<String, dynamic> map, String suffix) {
+    return new Map<String, dynamic>.fromIterables(
+      map.keys.map<String>((String key) => '$key$suffix'),
+      map.values,
+    );
+  }
+
+  static Future<Map<String, dynamic>> _compileAot({ bool previewDart2 = true }) async {
     // Generate blobs instead of assembly.
     await flutter('clean');
     final Stopwatch watch = new Stopwatch()..start();
@@ -230,6 +240,10 @@ class CompileTest {
         options.add('android-arm');
         break;
     }
+    if (previewDart2)
+      options.add('--preview-dart-2');
+    else
+      options.add('--no-preview-dart-2');
     setLocalEngineOptionIfNecessary(options);
     final String compileLog = await evalFlutter('build', options: options);
     watch.stop();
@@ -244,11 +258,15 @@ class CompileTest {
     return metrics;
   }
 
-  static Future<Map<String, dynamic>> _compileApp() async {
+  static Future<Map<String, dynamic>> _compileApp({ bool previewDart2 = true }) async {
     await flutter('clean');
     final Stopwatch watch = new Stopwatch();
     int releaseSizeInBytes;
     final List<String> options = <String>['--release'];
+    if (previewDart2)
+      options.add('--preview-dart-2');
+    else
+      options.add('--no-preview-dart-2');
     setLocalEngineOptionIfNecessary(options);
     switch (deviceOperatingSystem) {
       case DeviceOperatingSystem.ios:
@@ -281,10 +299,14 @@ class CompileTest {
     };
   }
 
-  static Future<Map<String, dynamic>> _compileDebug() async {
+  static Future<Map<String, dynamic>> _compileDebug({ bool previewDart2 = true }) async {
     await flutter('clean');
     final Stopwatch watch = new Stopwatch();
     final List<String> options = <String>['--debug'];
+    if (previewDart2)
+      options.add('--preview-dart-2');
+    else
+      options.add('--no-preview-dart-2');
     setLocalEngineOptionIfNecessary(options);
     switch (deviceOperatingSystem) {
       case DeviceOperatingSystem.ios:

dev/devicelab/manifest.yaml

@@ -154,6 +154,21 @@ tasks:
     stage: devicelab
     required_agent_capabilities: ["mac/android"]
 
+  hot_mode_dev_cycle__benchmark_dart1:
+    description: >
+      Measures the performance of Dart VM hot patching feature under
+      --no-preview-dart-2 option, that disables Dart 2.0 frontend.
+    stage: devicelab
+    required_agent_capabilities: ["mac/android"]
+
+  hot_mode_dev_cycle_ios__benchmark_dart1:
+    description: >
+      Measures the performance of Dart VM hot patching feature under
+      --no-preview-dart-2 option, that disables Dart 2.0 frontend.
+    stage: devicelab_ios
+    required_agent_capabilities: ["mac/ios"]
+    flaky: true
+
   complex_layout_scroll_perf__memory:
     description: >
       Measures memory usage of the scroll performance test.

packages/flutter_tools/bin/xcode_backend.sh

@@ -102,6 +102,13 @@ BuildApp() {
     local_engine_flag="--local-engine=$LOCAL_ENGINE"
   fi
 
+  local preview_dart_2_flag=""
+  if [[ -n "$PREVIEW_DART_2" ]]; then
+    preview_dart_2_flag="--preview-dart-2"
+  else
+    preview_dart_2_flag="--no-preview-dart-2"
+  fi
+
   local track_widget_creation_flag=""
   if [[ -n "$TRACK_WIDGET_CREATION" ]]; then
     track_widget_creation_flag="--track-widget-creation"
@@ -120,6 +127,7 @@ BuildApp() {
       --${build_mode}                                                       \
       --ios-arch="${archs}"                                                 \
       ${local_engine_flag}                                                  \
+      ${preview_dart_2_flag}                                                \
       ${track_widget_creation_flag}
 
     if [[ $? -ne 0 ]]; then
@@ -159,10 +167,12 @@ BuildApp() {
     ${verbose_flag}                                                         \
     build bundle                                                            \
     --target="${target_path}"                                               \
+    --snapshot="${build_dir}/snapshot_blob.bin"                             \
     --depfile="${build_dir}/snapshot_blob.bin.d"                            \
     --asset-dir="${derived_dir}/flutter_assets"                             \
     ${precompilation_flag}                                                  \
     ${local_engine_flag}                                                    \
+    ${preview_dart_2_flag}                                                  \
     ${track_widget_creation_flag}
 
   if [[ $? -ne 0 ]]; then

packages/flutter_tools/gradle/flutter.gradle

@@ -260,6 +260,10 @@ class FlutterPlugin implements Plugin<Project> {
         if (project.hasProperty('verbose')) {
             verboseValue = project.property('verbose').toBoolean()
         }
+        Boolean previewDart2Value = true
+        if (project.hasProperty('preview-dart-2')) {
+            previewDart2Value = project.property('preview-dart-2').toBoolean()
+        }
         String[] fileSystemRootsValue = null
         if (project.hasProperty('filesystem-roots')) {
             fileSystemRootsValue = project.property('filesystem-roots').split('\\|')
@@ -311,6 +315,7 @@ class FlutterPlugin implements Plugin<Project> {
                 localEngineSrcPath this.localEngineSrcPath
                 targetPath target
                 verbose verboseValue
+                previewDart2 previewDart2Value
                 fileSystemRoots fileSystemRootsValue
                 fileSystemScheme fileSystemSchemeValue
                 trackWidgetCreation trackWidgetCreationValue
@@ -355,6 +360,8 @@ abstract class BaseFlutterTask extends DefaultTask {
     @Optional @Input
     Boolean verbose
     @Optional @Input
+    Boolean previewDart2
+    @Optional @Input
     String[] fileSystemRoots
     @Optional @Input
     String fileSystemScheme
@@ -376,10 +383,12 @@ abstract class BaseFlutterTask extends DefaultTask {
         if (buildMode != 'debug') {
             // For AOT builds, include the gen_snapshot depfile.
             FileCollection depfiles = project.files("${intermediateDir}/snapshot.d")
-            // Include the kernel compiler depfile, since kernel compile is the
-            // first stage of AOT build in this mode, and it includes all the
-            // Dart sources.
-            depfiles += project.files("${intermediateDir}/kernel_compile.d")
+            if (previewDart2) {
+                // For Dart 2, also include the kernel compiler depfile, since
+                // kernel compile is the first stage of AOT build in this mode,
+                // and it includes all the Dart sources.
+                depfiles += project.files("${intermediateDir}/kernel_compile.d")
+            }
             return depfiles
         }
         return project.files("${intermediateDir}/snapshot_blob.bin.d")
@@ -406,6 +415,11 @@ abstract class BaseFlutterTask extends DefaultTask {
                 args "--target", targetPath
                 args "--target-platform", "android-arm"
                 args "--output-dir", "${intermediateDir}"
+                if (previewDart2) {
+                    args "--preview-dart-2"
+                } else {
+                    args "--no-preview-dart-2"
+                }
                 if (trackWidgetCreation) {
                     args "--track-widget-creation"
                 }
@@ -438,6 +452,11 @@ abstract class BaseFlutterTask extends DefaultTask {
             if (verbose) {
                 args "--verbose"
             }
+            if (previewDart2) {
+                args "--preview-dart-2"
+            } else {
+                args "--no-preview-dart-2"
+            }
             if (fileSystemRoots != null) {
                 for (root in fileSystemRoots) {
                     args "--filesystem-root", root
@@ -456,6 +475,9 @@ abstract class BaseFlutterTask extends DefaultTask {
                 args "--precompiled"
             } else {
                 args "--depfile", "${intermediateDir}/snapshot_blob.bin.d"
+                if (!previewDart2) {
+                    args "--snapshot", "${intermediateDir}/snapshot_blob.bin"
+                }
             }
             args "--asset-dir", "${intermediateDir}/flutter_assets"
         }
@@ -511,7 +533,9 @@ class FlutterTask extends BaseFlutterTask {
             // We have a dependencies file. Add a dependency on gen_snapshot as well, since the
             // snapshots have to be rebuilt if it changes.
             sources += readDependencies(project.file("${intermediateDir}/gen_snapshot.d"))
-            sources += readDependencies(project.file("${intermediateDir}/frontend_server.d"))
+            if (previewDart2) {
+                sources += readDependencies(project.file("${intermediateDir}/frontend_server.d"))
+            }
             if (localEngineSrcPath != null) {
                 sources += project.files("$localEngineSrcPath/$localEngine")
             }

packages/flutter_tools/lib/src/android/gradle.dart

@@ -327,16 +327,21 @@ Future<Null> _buildGradleProjectV2(String gradle, BuildInfo buildInfo, String ta
   if (target != null) {
     command.add('-Ptarget=$target');
   }
-  if (buildInfo.trackWidgetCreation)
-    command.add('-Ptrack-widget-creation=true');
-  if (buildInfo.extraFrontEndOptions != null)
-    command.add('-Pextra-front-end-options=${buildInfo.extraFrontEndOptions}');
-  if (buildInfo.extraGenSnapshotOptions != null)
-    command.add('-Pextra-gen-snapshot-options=${buildInfo.extraGenSnapshotOptions}');
-  if (buildInfo.fileSystemRoots != null && buildInfo.fileSystemRoots.isNotEmpty)
-    command.add('-Pfilesystem-roots=${buildInfo.fileSystemRoots.join('|')}');
-  if (buildInfo.fileSystemScheme != null)
-    command.add('-Pfilesystem-scheme=${buildInfo.fileSystemScheme}');
+  if (buildInfo.previewDart2) {
+    command.add('-Ppreview-dart-2=true');
+    if (buildInfo.trackWidgetCreation)
+      command.add('-Ptrack-widget-creation=true');
+    if (buildInfo.extraFrontEndOptions != null)
+      command.add('-Pextra-front-end-options=${buildInfo.extraFrontEndOptions}');
+    if (buildInfo.extraGenSnapshotOptions != null)
+      command.add('-Pextra-gen-snapshot-options=${buildInfo.extraGenSnapshotOptions}');
+    if (buildInfo.fileSystemRoots != null && buildInfo.fileSystemRoots.isNotEmpty)
+      command.add('-Pfilesystem-roots=${buildInfo.fileSystemRoots.join('|')}');
+    if (buildInfo.fileSystemScheme != null)
+      command.add('-Pfilesystem-scheme=${buildInfo.fileSystemScheme}');
+  } else {
+    command.add('-Ppreview-dart-2=false');
+  }
   if (buildInfo.buildSharedLibrary && androidSdk.ndk != null) {
     command.add('-Pbuild-shared-library=true');
   }

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

@@ -64,6 +64,70 @@ class GenSnapshot {
   }
 }
 
+/// Dart snapshot builder.
+///
+/// Builds Dart snapshots in one of three modes:
+///   * Script snapshot: architecture-independent snapshot of a Dart script
+///     and core libraries.
+///   * AOT snapshot: architecture-specific ahead-of-time compiled snapshot
+///     suitable for loading with `mmap`.
+///   * Assembly AOT snapshot: architecture-specific ahead-of-time compile to
+///     assembly suitable for compilation as a static or dynamic library.
+class ScriptSnapshotter {
+  /// Builds an architecture-independent snapshot of the specified script.
+  Future<int> build({
+    @required String mainPath,
+    @required String snapshotPath,
+    @required String depfilePath,
+    @required String packagesPath
+  }) async {
+    final SnapshotType snapshotType = new SnapshotType(null, BuildMode.debug);
+    final String vmSnapshotData = artifacts.getArtifactPath(Artifact.vmSnapshotData);
+    final String isolateSnapshotData = artifacts.getArtifactPath(Artifact.isolateSnapshotData);
+    final List<String> args = <String>[
+      '--snapshot_kind=script',
+      '--script_snapshot=$snapshotPath',
+      '--vm_snapshot_data=$vmSnapshotData',
+      '--isolate_snapshot_data=$isolateSnapshotData',
+      '--enable-mirrors=false',
+      mainPath,
+    ];
+
+    final Fingerprinter fingerprinter = new Fingerprinter(
+      fingerprintPath: '$depfilePath.fingerprint',
+      paths: <String>[
+        mainPath,
+        snapshotPath,
+        vmSnapshotData,
+        isolateSnapshotData,
+      ],
+      properties: <String, String>{
+        'buildMode': snapshotType.mode.toString(),
+        'targetPlatform': snapshotType.platform?.toString() ?? '',
+        'entryPoint': mainPath,
+      },
+      depfilePaths: <String>[depfilePath],
+    );
+    if (await fingerprinter.doesFingerprintMatch()) {
+      printTrace('Skipping script snapshot build. Fingerprints match.');
+      return 0;
+    }
+
+    // Build the snapshot.
+    final int exitCode = await genSnapshot.run(
+      snapshotType: snapshotType,
+      packagesPath: packagesPath,
+      depfilePath: depfilePath,
+      additionalArgs: args,
+    );
+
+    if (exitCode != 0)
+      return exitCode;
+    await fingerprinter.writeFingerprint();
+    return exitCode;
+  }
+}
+
 class AOTSnapshotter {
   /// Builds an architecture-specific ahead-of-time compiled snapshot of the specified script.
   Future<int> build({
@@ -72,6 +136,7 @@ class AOTSnapshotter {
     @required String mainPath,
     @required String packagesPath,
     @required String outputPath,
+    @required bool previewDart2,
     @required bool buildSharedLibrary,
     IOSArch iosArch,
     List<String> extraGenSnapshotOptions = const <String>[],
@@ -127,10 +192,12 @@ class AOTSnapshotter {
       '--embedder_entry_points_manifest=$ioEntryPoints',
       '--dependencies=$depfilePath',
     ];
-    genSnapshotArgs.addAll(<String>[
-      '--reify-generic-functions',
-      '--strong',
-    ]);
+    if (previewDart2) {
+      genSnapshotArgs.addAll(<String>[
+        '--reify-generic-functions',
+        '--strong',
+      ]);
+    }
     if (extraGenSnapshotOptions != null && extraGenSnapshotOptions.isNotEmpty) {
       printTrace('Extra gen_snapshot options: $extraGenSnapshotOptions');
       genSnapshotArgs.addAll(extraGenSnapshotOptions);
@@ -185,6 +252,7 @@ class AOTSnapshotter {
         'buildMode': buildMode.toString(),
         'targetPlatform': platform.toString(),
         'entryPoint': mainPath,
+        'dart2': previewDart2.toString(),
         'sharedLib': buildSharedLibrary.toString(),
         'extraGenSnapshotOptions': extraGenSnapshotOptions.join(' '),
       },

packages/flutter_tools/lib/src/build_info.dart

@@ -11,6 +11,7 @@ import 'globals.dart';
 /// Information about a build to be performed or used.
 class BuildInfo {
   const BuildInfo(this.mode, this.flavor, {
+    this.previewDart2 = false,
     this.trackWidgetCreation = false,
     this.extraFrontEndOptions,
     this.extraGenSnapshotOptions,
@@ -32,6 +33,9 @@ class BuildInfo {
   /// Mode-Flavor (e.g. Release-Paid).
   final String flavor;
 
+  /// Whether build should be done using Dart2 Frontend parser.
+  final bool previewDart2;
+
   final List<String> fileSystemRoots;
   final String fileSystemScheme;
 
@@ -89,6 +93,7 @@ class BuildInfo {
 
   BuildInfo withTargetPlatform(TargetPlatform targetPlatform) =>
       new BuildInfo(mode, flavor,
+          previewDart2: previewDart2,
           trackWidgetCreation: trackWidgetCreation,
           extraFrontEndOptions: extraFrontEndOptions,
           extraGenSnapshotOptions: extraGenSnapshotOptions,

packages/flutter_tools/lib/src/bundle.dart

@@ -6,6 +6,7 @@ import 'dart:async';
 
 import 'artifacts.dart';
 import 'asset.dart';
+import 'base/build.dart';
 import 'base/common.dart';
 import 'base/file_system.dart';
 import 'build_info.dart';
@@ -23,6 +24,7 @@ String get defaultApplicationKernelPath => fs.path.join(getBuildDirectory(), 'ap
 const String defaultPrivateKeyPath = 'privatekey.der';
 
 const String _kKernelKey = 'kernel_blob.bin';
+const String _kSnapshotKey = 'snapshot_blob.bin';
 const String _kVMSnapshotData = 'vm_snapshot_data';
 const String _kIsolateSnapshotData = 'isolate_snapshot_data';
 const String _kDylibKey = 'libapp.so';
@@ -31,11 +33,13 @@ const String _kPlatformKernelKey = 'platform.dill';
 Future<void> build({
   String mainPath = defaultMainPath,
   String manifestPath = defaultManifestPath,
+  String snapshotPath,
   String applicationKernelFilePath,
   String depfilePath,
   String privateKeyPath = defaultPrivateKeyPath,
   String assetDirPath,
   String packagesPath,
+  bool previewDart2  = false,
   bool precompiledSnapshot = false,
   bool reportLicensedPackages = false,
   bool trackWidgetCreation = false,
@@ -43,13 +47,32 @@ Future<void> build({
   List<String> fileSystemRoots,
   String fileSystemScheme,
 }) async {
+  snapshotPath ??= defaultSnapshotPath;
   depfilePath ??= defaultDepfilePath;
   assetDirPath ??= getAssetBuildDirectory();
   packagesPath ??= fs.path.absolute(PackageMap.globalPackagesPath);
   applicationKernelFilePath ??= defaultApplicationKernelPath;
+  File snapshotFile;
+
+  if (!precompiledSnapshot && !previewDart2) {
+    ensureDirectoryExists(snapshotPath);
+
+    // In a precompiled snapshot, the instruction buffer contains script
+    // content equivalents
+    final int result = await new ScriptSnapshotter().build(
+      mainPath: mainPath,
+      snapshotPath: snapshotPath,
+      depfilePath: depfilePath,
+      packagesPath: packagesPath,
+    );
+    if (result != 0)
+      throwToolExit('Failed to run the Flutter compiler. Exit code: $result', exitCode: result);
+
+    snapshotFile = fs.file(snapshotPath);
+  }
 
   DevFSContent kernelContent;
-  if (!precompiledSnapshot) {
+  if (!precompiledSnapshot && previewDart2) {
     if ((extraFrontEndOptions != null) && extraFrontEndOptions.isNotEmpty)
       printTrace('Extra front-end options: $extraFrontEndOptions');
     ensureDirectoryExists(applicationKernelFilePath);
@@ -86,6 +109,7 @@ Future<void> build({
   await assemble(
     assetBundle: assets,
     kernelContent: kernelContent,
+    snapshotFile: snapshotFile,
     privateKeyPath: privateKeyPath,
     assetDirPath: assetDirPath,
   );
@@ -119,6 +143,7 @@ Future<AssetBundle> buildAssets({
 Future<void> assemble({
   AssetBundle assetBundle,
   DevFSContent kernelContent,
+  File snapshotFile,
   File dylibFile,
   String privateKeyPath = defaultPrivateKeyPath,
   String assetDirPath,
@@ -127,16 +152,21 @@ Future<void> assemble({
   printTrace('Building bundle');
 
   final Map<String, DevFSContent> assetEntries = new Map<String, DevFSContent>.from(assetBundle.entries);
+  final String vmSnapshotData = artifacts.getArtifactPath(Artifact.vmSnapshotData);
+  final String isolateSnapshotData = artifacts.getArtifactPath(Artifact.isolateSnapshotData);
 
   if (kernelContent != null) {
     final String platformKernelDill = artifacts.getArtifactPath(Artifact.platformKernelDill);
-    final String vmSnapshotData = artifacts.getArtifactPath(Artifact.vmSnapshotData);
-    final String isolateSnapshotData = artifacts.getArtifactPath(Artifact.isolateSnapshotData);
     assetEntries[_kKernelKey] = kernelContent;
     assetEntries[_kPlatformKernelKey] = new DevFSFileContent(fs.file(platformKernelDill));
     assetEntries[_kVMSnapshotData] = new DevFSFileContent(fs.file(vmSnapshotData));
     assetEntries[_kIsolateSnapshotData] = new DevFSFileContent(fs.file(isolateSnapshotData));
   }
+  if (snapshotFile != null) {
+    assetEntries[_kSnapshotKey] = new DevFSFileContent(snapshotFile);
+    assetEntries[_kVMSnapshotData] = new DevFSFileContent(fs.file(vmSnapshotData));
+    assetEntries[_kIsolateSnapshotData] = new DevFSFileContent(fs.file(isolateSnapshotData));
+  }
   if (dylibFile != null)
     assetEntries[_kDylibKey] = new DevFSFileContent(dylibFile);
 

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

@@ -26,6 +26,8 @@ class AnalyzeCommand extends FlutterCommand {
     argParser.addFlag('watch',
         help: 'Run analysis continuously, watching the filesystem for changes.',
         negatable: false);
+    argParser.addFlag('preview-dart-2',
+        defaultsTo: true, help: 'Preview Dart 2.0 functionality.');
     argParser.addOption('write',
         valueHelp: 'file',
         help: 'Also output the results to a file. This is useful with --watch '
@@ -85,6 +87,7 @@ class AnalyzeCommand extends FlutterCommand {
         argResults,
         runner.getRepoRoots(),
         runner.getRepoPackages(),
+        previewDart2: argResults['preview-dart-2'],
       ).analyze();
     } else {
       return new AnalyzeOnce(
@@ -92,6 +95,7 @@ class AnalyzeCommand extends FlutterCommand {
         runner.getRepoRoots(),
         runner.getRepoPackages(),
         workingDirectory: workingDirectory,
+        previewDart2: argResults['preview-dart-2'],
       ).analyze();
     }
   }

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

@@ -19,10 +19,13 @@ import '../globals.dart';
 import 'analyze_base.dart';
 
 class AnalyzeContinuously extends AnalyzeBase {
-  AnalyzeContinuously(ArgResults argResults, this.repoRoots, this.repoPackages) : super(argResults);
+  AnalyzeContinuously(ArgResults argResults, this.repoRoots, this.repoPackages, {
+    this.previewDart2 = false,
+  }) : super(argResults);
 
   final List<String> repoRoots;
   final List<Directory> repoPackages;
+  final bool previewDart2;
 
   String analysisTarget;
   bool firstAnalysis = true;
@@ -57,7 +60,7 @@ class AnalyzeContinuously extends AnalyzeBase {
 
     final String sdkPath = argResults['dart-sdk'] ?? sdk.dartSdkPath;
 
-    final AnalysisServer server = new AnalysisServer(sdkPath, directories);
+    final AnalysisServer server = new AnalysisServer(sdkPath, directories, previewDart2: previewDart2);
     server.onAnalyzing.listen((bool isAnalyzing) => _handleAnalysisStatus(server, isAnalyzing));
     server.onErrors.listen(_handleAnalysisErrors);
 

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

@@ -24,6 +24,7 @@ class AnalyzeOnce extends AnalyzeBase {
     this.repoRoots,
     this.repoPackages, {
     this.workingDirectory,
+    this.previewDart2 = false,
   }) : super(argResults);
 
   final List<String> repoRoots;
@@ -32,6 +33,8 @@ class AnalyzeOnce extends AnalyzeBase {
   /// The working directory for testing analysis using dartanalyzer.
   final Directory workingDirectory;
 
+  final bool previewDart2;
+
   @override
   Future<Null> analyze() async {
     final String currentDirectory =
@@ -88,6 +91,7 @@ class AnalyzeOnce extends AnalyzeBase {
     final AnalysisServer server = new AnalysisServer(
       sdkPath,
       directories.toList(),
+      previewDart2: previewDart2,
     );
 
     StreamSubscription<bool> subscription;

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

@@ -28,6 +28,11 @@ class BuildAotCommand extends BuildSubCommand {
         allowed: <String>['android-arm', 'android-arm64', 'ios']
       )
       ..addFlag('quiet', defaultsTo: false)
+      ..addFlag('preview-dart-2',
+        defaultsTo: true,
+        hide: !verboseHelp,
+        help: 'Preview Dart 2.0 functionality.',
+      )
       ..addFlag('build-shared-library',
         negatable: false,
         defaultsTo: false,
@@ -74,20 +79,23 @@ class BuildAotCommand extends BuildSubCommand {
     }
     final String outputPath = argResults['output-dir'] ?? getAotBuildDirectory();
     try {
+      final bool previewDart2 = argResults['preview-dart-2'];
       String mainPath = findMainDartFile(targetFile);
       final AOTSnapshotter snapshotter = new AOTSnapshotter();
 
-      // Compile to kernel.
-      mainPath = await snapshotter.compileKernel(
-        platform: platform,
-        buildMode: buildMode,
-        mainPath: mainPath,
-        outputPath: outputPath,
-        extraFrontEndOptions: argResults[FlutterOptions.kExtraFrontEndOptions],
-      );
-      if (mainPath == null) {
-        printError('Compiler terminated unexpectedly.');
-        return;
+      // Compile to kernel, if Dart 2.
+      if (previewDart2) {
+        mainPath = await snapshotter.compileKernel(
+          platform: platform,
+          buildMode: buildMode,
+          mainPath: mainPath,
+          outputPath: outputPath,
+          extraFrontEndOptions: argResults[FlutterOptions.kExtraFrontEndOptions],
+        );
+        if (mainPath == null) {
+          printError('Compiler terminated unexpectedly.');
+          return;
+        }
       }
 
       // Build AOT snapshot.
@@ -108,6 +116,7 @@ class BuildAotCommand extends BuildSubCommand {
             mainPath: mainPath,
             packagesPath: PackageMap.globalPackagesPath,
             outputPath: outputPath,
+            previewDart2: previewDart2,
             buildSharedLibrary: false,
             extraGenSnapshotOptions: argResults[FlutterOptions.kExtraGenSnapshotOptions],
           ).then((int buildExitCode) {
@@ -134,6 +143,7 @@ class BuildAotCommand extends BuildSubCommand {
           mainPath: mainPath,
           packagesPath: PackageMap.globalPackagesPath,
           outputPath: outputPath,
+          previewDart2: previewDart2,
           buildSharedLibrary: argResults['build-shared-library'],
           extraGenSnapshotOptions: argResults[FlutterOptions.kExtraGenSnapshotOptions],
         );

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

@@ -17,6 +17,11 @@ class BuildApkCommand extends BuildSubCommand {
     usesBuildNameOption();
 
     argParser
+      ..addFlag('preview-dart-2',
+        defaultsTo: true,
+        hide: !verboseHelp,
+        help: 'Preview Dart 2.0 functionality.',
+      )
       ..addFlag('track-widget-creation', negatable: false, hide: !verboseHelp)
       ..addFlag('build-shared-library',
         negatable: false,

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

@@ -19,8 +19,14 @@ class BuildBundleCommand extends BuildSubCommand {
       ..addOption('asset-base', help: 'Ignored. Will be removed.', hide: !verboseHelp)
       ..addOption('manifest', defaultsTo: defaultManifestPath)
       ..addOption('private-key', defaultsTo: defaultPrivateKeyPath)
+      ..addOption('snapshot', defaultsTo: defaultSnapshotPath)
       ..addOption('depfile', defaultsTo: defaultDepfilePath)
       ..addOption('kernel-file', defaultsTo: defaultApplicationKernelPath)
+      ..addFlag('preview-dart-2',
+        defaultsTo: true,
+        hide: !verboseHelp,
+        help: 'Preview Dart 2.0 functionality.',
+      )
       ..addFlag('track-widget-creation',
         hide: !verboseHelp,
         help: 'Track widget creation locations. Requires Dart 2.0 functionality.',
@@ -66,10 +72,12 @@ class BuildBundleCommand extends BuildSubCommand {
     await build(
       mainPath: targetFile,
       manifestPath: argResults['manifest'],
+      snapshotPath: argResults['snapshot'],
       applicationKernelFilePath: argResults['kernel-file'],
       depfilePath: argResults['depfile'],
       privateKeyPath: argResults['private-key'],
       assetDirPath: argResults['asset-dir'],
+      previewDart2: argResults['preview-dart-2'],
       precompiledSnapshot: argResults['precompiled'],
       reportLicensedPackages: argResults['report-licensed-packages'],
       trackWidgetCreation: argResults['track-widget-creation'],

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

@@ -38,7 +38,11 @@ class BuildIOSCommand extends BuildSubCommand {
       ..addFlag('codesign',
         defaultsTo: true,
         help: 'Codesign the application bundle (only available on device builds).',
-      );
+      )
+      ..addFlag('preview-dart-2',
+        defaultsTo: true,
+        hide: !verboseHelp,
+        help: 'Preview Dart 2.0 functionality.');
   }
 
   @override

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

@@ -334,6 +334,7 @@ class AppDomain extends Domain {
     final BuildInfo buildInfo = new BuildInfo(
       getBuildModeForName(mode) ?? BuildMode.debug,
       flavor,
+      previewDart2: _getBoolArg(args, 'preview-dart-2'),
     );
     DebuggingOptions options;
     if (buildInfo.isRelease) {
@@ -384,6 +385,7 @@ class AppDomain extends Domain {
 
     final FlutterDevice flutterDevice = new FlutterDevice(
       device,
+      previewDart2: options.buildInfo.previewDart2,
       trackWidgetCreation: trackWidgetCreation,
       dillOutputPath: dillOutputPath,
     );

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

@@ -62,7 +62,10 @@ class DriveCommand extends RunCommandBase {
               'just before the extension, so e.g. if the target is "lib/main.dart", the\n'
               'driver will be "test_driver/main_test.dart".',
         valueHelp: 'path',
-      );
+      )
+      ..addFlag('preview-dart-2',
+        defaultsTo: true,
+        help: 'Preview Dart 2.0 functionality.');
   }
 
   @override
@@ -120,7 +123,7 @@ class DriveCommand extends RunCommandBase {
     Cache.releaseLockEarly();
 
     try {
-      await testRunner(<String>[testFile], observatoryUri);
+      await testRunner(<String>[testFile], observatoryUri, argResults['preview-dart-2']);
     } catch (error, stackTrace) {
       if (error is ToolExit)
         rethrow;
@@ -272,20 +275,24 @@ Future<LaunchResult> _startApp(DriveCommand command) async {
 }
 
 /// Runs driver tests.
-typedef Future<Null> TestRunner(List<String> testArgs, String observatoryUri);
+typedef Future<Null> TestRunner(List<String> testArgs, String observatoryUri, bool previewDart2);
 TestRunner testRunner = _runTests;
 void restoreTestRunner() {
   testRunner = _runTests;
 }
 
-Future<Null> _runTests(List<String> testArgs, String observatoryUri) async {
+Future<Null> _runTests(List<String> testArgs, String observatoryUri, bool previewDart2) async {
   printTrace('Running driver tests.');
 
   PackageMap.globalPackagesPath = fs.path.normalize(fs.path.absolute(PackageMap.globalPackagesPath));
   final List<String> args = testArgs.toList()
     ..add('--packages=${PackageMap.globalPackagesPath}')
-    ..add('-rexpanded')
-    ..add('--preview-dart-2');
+    ..add('-rexpanded');
+  if (previewDart2) {
+    args.add('--preview-dart-2');
+  } else {
+    args.add('--no-preview-dart-2');
+  }
 
   final String dartVmPath = fs.path.join(dartSdkPath, 'bin', 'dart');
   final int result = await runCommandAndStreamOutput(

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

@@ -53,6 +53,10 @@ class FuchsiaReloadCommand extends FlutterCommand {
     argParser.addOption('name-override',
       abbr: 'n',
       help: 'On-device name of the application binary.');
+    argParser.addFlag('preview-dart-2',
+      abbr: '2',
+      defaultsTo: false,
+      help: 'Preview Dart 2.0 functionality.');
     argParser.addOption('target',
       abbr: 't',
       defaultsTo: bundle.defaultMainPath,
@@ -128,8 +132,13 @@ class FuchsiaReloadCommand extends FlutterCommand {
       final List<Uri> observatoryUris = fullAddresses.map(
         (String a) => Uri.parse('http://$a')
       ).toList();
-      final FuchsiaDevice device = new FuchsiaDevice(fullAddresses[0], name: _address);
-      final FlutterDevice flutterDevice = new FlutterDevice(device, trackWidgetCreation: false);
+      final FuchsiaDevice device = new FuchsiaDevice(
+          fullAddresses[0], name: _address);
+      final FlutterDevice flutterDevice = new FlutterDevice(
+        device,
+        trackWidgetCreation: false,
+        previewDart2: false,
+      );
       flutterDevice.observatoryUris = observatoryUris;
       final HotRunner hotRunner = new HotRunner(
         <FlutterDevice>[flutterDevice],

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

@@ -120,6 +120,11 @@ class RunCommand extends RunCommandBase {
         hide: !verboseHelp,
         help: 'Specify a pre-built application binary to use when running.',
       )
+      ..addFlag('preview-dart-2',
+        defaultsTo: true,
+        hide: !verboseHelp,
+        help: 'Preview Dart 2.0 functionality.',
+      )
       ..addFlag('track-widget-creation',
         hide: !verboseHelp,
         help: 'Track widget creation locations. Requires Dart 2.0 functionality.',
@@ -342,6 +347,7 @@ class RunCommand extends RunCommandBase {
     final List<FlutterDevice> flutterDevices = devices.map((Device device) {
       return new FlutterDevice(
         device,
+        previewDart2: argResults['preview-dart-2'],
         trackWidgetCreation: argResults['track-widget-creation'],
         dillOutputPath: argResults['output-dill'],
         fileSystemRoots: argResults['filesystem-root'],

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

@@ -68,6 +68,11 @@ class TestCommand extends FlutterCommand {
         help: 'Handle machine structured JSON command input\n'
               'and provide output and progress in machine friendly format.',
       )
+      ..addFlag('preview-dart-2',
+        defaultsTo: true,
+        hide: !verboseHelp,
+        help: 'Preview Dart 2.0 functionality.',
+      )
       ..addFlag('track-widget-creation',
         negatable: false,
         hide: !verboseHelp,
@@ -218,6 +223,7 @@ class TestCommand extends FlutterCommand {
       startPaused: startPaused,
       ipv6: argResults['ipv6'],
       machine: machine,
+      previewDart2: argResults['preview-dart-2'],
       trackWidgetCreation: argResults['track-widget-creation'],
       updateGoldens: argResults['update-goldens'],
     );

packages/flutter_tools/lib/src/dart/analysis.dart

@@ -13,10 +13,11 @@ import '../base/process_manager.dart';
 import '../globals.dart';
 
 class AnalysisServer {
-  AnalysisServer(this.sdkPath, this.directories);
+  AnalysisServer(this.sdkPath, this.directories, {this.previewDart2 = false});
 
   final String sdkPath;
   final List<String> directories;
+  final bool previewDart2;
 
   Process _process;
   final StreamController<bool> _analyzingController =
@@ -34,9 +35,14 @@ class AnalysisServer {
       snapshot,
       '--sdk',
       sdkPath,
-      '--preview-dart-2',
     ];
 
+    if (previewDart2) {
+      command.add('--preview-dart-2');
+    } else {
+      command.add('--no-preview-dart-2');
+    }
+
     printTrace('dart ${command.skip(1).join(' ')}');
     _process = await processManager.start(command);
     // This callback hookup can't throw.

packages/flutter_tools/lib/src/devfs.dart

@@ -6,7 +6,6 @@ import 'dart:async';
 import 'dart:convert' show base64, utf8;
 
 import 'package:json_rpc_2/json_rpc_2.dart' as rpc;
-import 'package:meta/meta.dart';
 
 import 'asset.dart';
 import 'base/context.dart';
@@ -402,14 +401,14 @@ class DevFS {
   ///
   /// Returns the number of bytes synced.
   Future<int> update({
-    @required String mainPath,
+    String mainPath,
     String target,
     AssetBundle bundle,
     DateTime firstBuildTime,
     bool bundleFirstUpload = false,
     bool bundleDirty = false,
     Set<String> fileFilter,
-    @required ResidentCompiler generator,
+    ResidentCompiler generator,
     String dillOutputPath,
     bool fullRestart = false,
     String projectRootPath,
@@ -425,9 +424,10 @@ class DevFS {
     await _scanDirectory(rootDirectory,
                          recursive: true,
                          fileFilter: fileFilter);
+    final bool previewDart2 = generator != null;
     if (fs.isFileSync(_packagesFilePath)) {
       printTrace('Scanning package files');
-      await _scanPackages(fileFilter);
+      await _scanPackages(fileFilter, previewDart2);
     }
     if (bundle != null) {
       printTrace('Scanning asset files');
@@ -468,9 +468,10 @@ class DevFS {
       String archivePath;
       if (deviceUri.path.startsWith(assetBuildDirPrefix))
         archivePath = deviceUri.path.substring(assetBuildDirPrefix.length);
-      // When doing full restart in, copy content so that isModified does not
-      // reset last check timestamp because we want to report all modified
-      // files to incremental compiler next time user does hot reload.
+      // When doing full restart in preview-dart-2 mode, copy content so
+      // that isModified does not reset last check timestamp because we
+      // want to report all modified files to incremental compiler next time
+      // user does hot reload.
       if (content.isModified || ((bundleDirty || bundleFirstUpload) && archivePath != null)) {
         dirtyEntries[deviceUri] = content;
         numBytes += content.size;
@@ -478,24 +479,24 @@ class DevFS {
           assetPathsToEvict.add(archivePath);
       }
     });
-
-    // We run generator even if [dirtyEntries] was empty because we want to
-    // keep logic of accepting/rejecting generator's output simple: we must
-    // accept/reject generator's output after every [update] call.  Incremental
-    // run with no changes is supposed to be fast (considering that it is
-    // initiated by user key press).
-    final List<String> invalidatedFiles = <String>[];
-    final Set<Uri> filesUris = new Set<Uri>();
-    for (Uri uri in dirtyEntries.keys.toList()) {
-      if (!uri.path.startsWith(assetBuildDirPrefix)) {
-        final DevFSContent content = dirtyEntries[uri];
-        if (content is DevFSFileContent) {
-          filesUris.add(uri);
-          invalidatedFiles.add(content.file.uri.toString());
-          numBytes -= content.size;
+    if (previewDart2) {
+      // We run generator even if [dirtyEntries] was empty because we want
+      // to keep logic of accepting/rejecting generator's output simple:
+      // we must accept/reject generator's output after every [update] call.
+      // Incremental run with no changes is supposed to be fast (considering
+      // that it is initiated by user key press).
+      final List<String> invalidatedFiles = <String>[];
+      final Set<Uri> filesUris = new Set<Uri>();
+      for (Uri uri in dirtyEntries.keys.toList()) {
+        if (!uri.path.startsWith(assetBuildDirPrefix)) {
+          final DevFSContent content = dirtyEntries[uri];
+          if (content is DevFSFileContent) {
+            filesUris.add(uri);
+            invalidatedFiles.add(content.file.uri.toString());
+            numBytes -= content.size;
+          }
         }
       }
-
       // No need to send source files because all compilation is done on the
       // host and result of compilation is single kernel file.
       filesUris.forEach(dirtyEntries.remove);
@@ -503,12 +504,10 @@ class DevFS {
       if (fullRestart) {
         generator.reset();
       }
-      final CompilerOutput compilerOutput = await generator.recompile(
-        mainPath,
-        invalidatedFiles,
-        outputPath:  dillOutputPath ?? fs.path.join(getBuildDirectory(), 'app.dill'),
-        packagesFilePath : _packagesFilePath,
-      );
+      final CompilerOutput compilerOutput =
+          await generator.recompile(mainPath, invalidatedFiles,
+              outputPath:  dillOutputPath ?? fs.path.join(getBuildDirectory(), 'app.dill'),
+              packagesFilePath : _packagesFilePath);
       final String compiledBinary = compilerOutput?.outputFilename;
       if (compiledBinary != null && compiledBinary.isNotEmpty) {
         final String entryUri = projectRootPath != null ?
@@ -698,7 +697,7 @@ class DevFS {
     );
   }
 
-  Future<Null> _scanPackages(Set<String> fileFilter) async {
+  Future<Null> _scanPackages(Set<String> fileFilter, bool previewDart2) async {
     StringBuffer sb;
     final PackageMap packageMap = new PackageMap(_packagesFilePath);
 
@@ -731,6 +730,22 @@ class DevFS {
         sb.writeln('$packageName:$directoryUriOnDevice');
       }
     }
+    if (previewDart2) {
+      // When in previewDart2 mode we don't update .packages-file entry
+      // so actual file will get invalidated in frontend.
+      // We don't need to synthesize device-correct .packages file because
+      // it is not going to be used on the device anyway - compilation
+      // is done on the host.
+      return;
+    }
+    if (sb != null) {
+      final DevFSContent content = _entries[fs.path.toUri('.packages')];
+      if (content is DevFSStringContent && content.string == sb.toString()) {
+        content._exists = true;
+        return;
+      }
+      _entries[fs.path.toUri('.packages')] = new DevFSStringContent(sb.toString());
+    }
   }
 }
 /// Converts a platform-specific file path to a platform-independent Uri path.

packages/flutter_tools/lib/src/ios/mac.dart

@@ -246,6 +246,7 @@ Future<XcodeBuildResult> buildXcodeProject({
     projectPath: fs.currentDirectory.path,
     buildInfo: buildInfo,
     targetOverride: targetOverride,
+    previewDart2: buildInfo.previewDart2,
   );
 
   if (hasPlugins()) {
@@ -427,7 +428,7 @@ Future<XcodeBuildResult> buildXcodeProject({
       outputDir = expectedOutputDirectory.replaceFirst('/$configuration-', '/');
       if (fs.isDirectorySync(outputDir)) {
         // Previous output directory might have incompatible artifacts
-        // (for example, kernel binary files produced from previous run).
+        // (for example, kernel binary files produced from previous `--preview-dart-2` run).
         fs.directory(outputDir).deleteSync(recursive: true);
       }
       copyDirectorySync(fs.directory(expectedOutputDirectory), fs.directory(outputDir));

packages/flutter_tools/lib/src/ios/simulators.dart

@@ -362,6 +362,7 @@ class IOSSimulator extends Device {
     // The build mode for the simulator is always debug.
 
     final BuildInfo debugBuildInfo = new BuildInfo(BuildMode.debug, buildInfo.flavor,
+        previewDart2: buildInfo.previewDart2,
         trackWidgetCreation: buildInfo.trackWidgetCreation,
         extraFrontEndOptions: buildInfo.extraFrontEndOptions,
         extraGenSnapshotOptions: buildInfo.extraGenSnapshotOptions,
@@ -389,10 +390,12 @@ class IOSSimulator extends Device {
   }
 
   Future<Null> _sideloadUpdatedAssetsForInstalledApplicationBundle(ApplicationPackage app, BuildInfo buildInfo, String mainPath) {
-    // Run compiler to produce kernel file for the application.
+    // When running in previewDart2 mode, we still need to run compiler to
+    // produce kernel file for the application.
     return bundle.build(
       mainPath: mainPath,
-      precompiledSnapshot: false,
+      precompiledSnapshot: !buildInfo.previewDart2,
+      previewDart2: buildInfo.previewDart2,
       trackWidgetCreation: buildInfo.trackWidgetCreation,
     );
   }

packages/flutter_tools/lib/src/ios/xcodeproj.dart

@@ -42,6 +42,7 @@ Future<void> generateXcodeProperties(String projectPath) async {
       projectPath: projectPath,
       buildInfo: BuildInfo.debug,
       targetOverride: bundle.defaultMainPath,
+      previewDart2: false,
     );
   }
 }
@@ -54,6 +55,7 @@ Future<void> updateGeneratedXcodeProperties({
   @required String projectPath,
   @required BuildInfo buildInfo,
   String targetOverride,
+  @required bool previewDart2,
 }) async {
   final StringBuffer localsBuffer = new StringBuffer();
 
@@ -111,6 +113,10 @@ Future<void> updateGeneratedXcodeProperties({
     localsBuffer.writeln('ARCHS=$arch');
   }
 
+  if (previewDart2) {
+    localsBuffer.writeln('PREVIEW_DART_2=true');
+  }
+
   if (buildInfo.trackWidgetCreation) {
     localsBuffer.writeln('TRACK_WIDGET_CREATION=true');
   }

packages/flutter_tools/lib/src/resident_runner.dart

@@ -34,7 +34,7 @@ class FlutterDevice {
   List<VMService> vmServices;
   DevFS devFS;
   ApplicationPackage package;
-  final ResidentCompiler generator;
+  ResidentCompiler generator;
   String dillOutputPath;
   List<String> fileSystemRoots;
   String fileSystemScheme;
@@ -42,15 +42,20 @@ class FlutterDevice {
   StreamSubscription<String> _loggingSubscription;
 
   FlutterDevice(this.device, {
+    @required bool previewDart2,
     @required bool trackWidgetCreation,
     this.dillOutputPath,
     this.fileSystemRoots,
     this.fileSystemScheme,
-  }) : generator = new ResidentCompiler(
-      artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath),
-      trackWidgetCreation: trackWidgetCreation,
-      fileSystemRoots: fileSystemRoots,
-      fileSystemScheme: fileSystemScheme);
+  }) {
+    if (previewDart2) {
+      generator = new ResidentCompiler(
+        artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath),
+        trackWidgetCreation: trackWidgetCreation,
+        fileSystemRoots: fileSystemRoots, fileSystemScheme: fileSystemScheme
+      );
+    }
+  }
 
   String viewFilter;
 
@@ -407,9 +412,9 @@ class FlutterDevice {
 
   void updateReloadStatus(bool wasReloadSuccessful) {
     if (wasReloadSuccessful)
-      generator.accept();
+      generator?.accept();
     else
-      generator.reject();
+      generator?.reject();
   }
 }
 

packages/flutter_tools/lib/src/run_hot.dart

@@ -412,11 +412,15 @@ class HotRunner extends ResidentRunner {
     }
     // We are now running from source.
     _runningFromSnapshot = false;
-
-    await _launchFromDevFS('$mainPath.dill');
+    final String launchPath = debuggingOptions.buildInfo.previewDart2
+        ? mainPath + '.dill'
+        : mainPath;
+    await _launchFromDevFS(launchPath);
     restartTimer.stop();
-    printTrace('Restart performed in ${getElapsedAsMilliseconds(restartTimer.elapsed)}.');
-
+    printTrace('Restart performed in '
+        '${getElapsedAsMilliseconds(restartTimer.elapsed)}.');
+    // We are now running from sources.
+    _runningFromSnapshot = false;
     _addBenchmarkData('hotRestartMillisecondsToFrame',
         restartTimer.elapsed.inMilliseconds);
     flutterUsage.sendEvent('hot', 'restart');
@@ -506,6 +510,14 @@ class HotRunner extends ResidentRunner {
     }
   }
 
+  String _uriToRelativePath(Uri uri) {
+    final String path = uri.toString();
+    final String base = new Uri.file(projectRootPath).toString();
+    if (path.startsWith(base))
+      return path.substring(base.length + 1);
+    return path;
+  }
+
   Future<OperationResult> _reloadSources({ bool pause = false }) async {
     for (FlutterDevice device in flutterDevices) {
       for (FlutterView view in device.views) {
@@ -525,6 +537,7 @@ class HotRunner extends ResidentRunner {
     // change from host path to a device path). Subsequent reloads will
     // not be affected, so we resume reporting reload times on the second
     // reload.
+    final bool reportUnused = !debuggingOptions.buildInfo.previewDart2;
     final bool shouldReportReloadTime = !_runningFromSnapshot;
     final Stopwatch reloadTimer = new Stopwatch()..start();
 
@@ -538,7 +551,10 @@ class HotRunner extends ResidentRunner {
     String reloadMessage;
     final Stopwatch vmReloadTimer = new Stopwatch()..start();
     try {
-      final String entryPath = fs.path.relative('$mainPath.dill', from: projectRootPath);
+      final String entryPath = fs.path.relative(
+        debuggingOptions.buildInfo.previewDart2 ? mainPath + '.dill' : mainPath,
+        from: projectRootPath,
+      );
       final Completer<Map<String, dynamic>> retrieveFirstReloadReport = new Completer<Map<String, dynamic>>();
 
       int countExpectedReports = 0;
@@ -550,7 +566,10 @@ class HotRunner extends ResidentRunner {
         }
 
         // List has one report per Flutter view.
-        final List<Future<Map<String, dynamic>>> reports = device.reloadSources(entryPath, pause: pause);
+        final List<Future<Map<String, dynamic>>> reports = device.reloadSources(
+          entryPath,
+          pause: pause
+        );
         countExpectedReports += reports.length;
         Future.wait(reports).catchError((dynamic error) {
           return <Map<String, dynamic>>[error];
@@ -618,8 +637,8 @@ class HotRunner extends ResidentRunner {
     }
     // We are now running from source.
     _runningFromSnapshot = false;
-
     // Check if the isolate is paused.
+
     final List<FlutterView> reassembleViews = <FlutterView>[];
     for (FlutterDevice device in flutterDevices) {
       for (FlutterView view in device.views) {
@@ -680,9 +699,36 @@ class HotRunner extends ResidentRunner {
         shouldReportReloadTime)
       flutterUsage.sendTiming('hot', 'reload', reloadTimer.elapsed);
 
+    String unusedElementMessage;
+    if (reportUnused && !reassembleAndScheduleErrors && !reassembleTimedOut) {
+      final List<Future<List<ProgramElement>>> unusedReports =
+        <Future<List<ProgramElement>>>[];
+      for (FlutterDevice device in flutterDevices)
+        unusedReports.add(device.unusedChangesInLastReload());
+      final List<ProgramElement> unusedElements = <ProgramElement>[];
+      for (Future<List<ProgramElement>> unusedReport in unusedReports)
+        unusedElements.addAll(await unusedReport);
+
+      if (unusedElements.isNotEmpty) {
+        final String restartCommand = hostIsIde ? '' : ' (by pressing "R")';
+        unusedElementMessage =
+          'Some program elements were changed during reload but did not run when the view was reassembled;\n'
+          'you may need to restart the app$restartCommand for the changes to have an effect.';
+        for (ProgramElement unusedElement in unusedElements) {
+          final String name = unusedElement.qualifiedName;
+          final String path = _uriToRelativePath(unusedElement.uri);
+          final int line = unusedElement.line;
+          final String description = line == null ? '$name ($path)' : '$name ($path:$line)';
+          unusedElementMessage += '\n  • $description';
+        }
+      }
+    }
+
     return new OperationResult(
       reassembleAndScheduleErrors ? 1 : OperationResult.ok.code,
       reloadMessage,
+      hintMessage: unusedElementMessage,
+      hintId: unusedElementMessage != null ? 'restartRecommended' : null,
     );
   }
 

packages/flutter_tools/lib/src/runner/flutter_command.dart

@@ -182,6 +182,10 @@ abstract class FlutterCommand extends Command<Null> {
   }
 
   BuildInfo getBuildInfo() {
+    final bool previewDart2 = argParser.options.containsKey('preview-dart-2')
+        ? argResults['preview-dart-2']
+        : true;
+
     TargetPlatform targetPlatform;
     if (argParser.options.containsKey('target-platform') &&
         argResults['target-platform'] != 'default') {
@@ -191,6 +195,10 @@ abstract class FlutterCommand extends Command<Null> {
     final bool trackWidgetCreation = argParser.options.containsKey('track-widget-creation')
         ? argResults['track-widget-creation']
         : false;
+    if (trackWidgetCreation == true && previewDart2 == false) {
+      throw new UsageException(
+          '--track-widget-creation is valid only when --preview-dart-2 is specified.', null);
+    }
 
     int buildNumber;
     try {
@@ -206,6 +214,7 @@ abstract class FlutterCommand extends Command<Null> {
       argParser.options.containsKey('flavor')
         ? argResults['flavor']
         : null,
+      previewDart2: previewDart2,
       trackWidgetCreation: trackWidgetCreation,
       extraFrontEndOptions: argParser.options.containsKey(FlutterOptions.kExtraFrontEndOptions)
           ? argResults[FlutterOptions.kExtraFrontEndOptions]

packages/flutter_tools/lib/src/test/flutter_platform.dart

@@ -67,6 +67,7 @@ void installHook({
   bool enableObservatory = false,
   bool machine = false,
   bool startPaused = false,
+  bool previewDart2 = false,
   int port = 0,
   String precompiledDillPath,
   bool trackWidgetCreation = false,
@@ -85,6 +86,7 @@ void installHook({
       startPaused: startPaused,
       explicitObservatoryPort: observatoryPort,
       host: _kHosts[serverType],
+      previewDart2: previewDart2,
       port: port,
       precompiledDillPath: precompiledDillPath,
       trackWidgetCreation: trackWidgetCreation,
@@ -304,6 +306,7 @@ class _FlutterPlatform extends PlatformPlugin {
     this.startPaused,
     this.explicitObservatoryPort,
     this.host,
+    this.previewDart2,
     this.port,
     this.precompiledDillPath,
     this.trackWidgetCreation,
@@ -317,6 +320,7 @@ class _FlutterPlatform extends PlatformPlugin {
   final bool startPaused;
   final int explicitObservatoryPort;
   final InternetAddress host;
+  final bool previewDart2;
   final int port;
   final String precompiledDillPath;
   final bool trackWidgetCreation;
@@ -404,15 +408,17 @@ class _FlutterPlatform extends PlatformPlugin {
         cancelOnError: true,
       );
 
-      printTrace('test $ourTestCount: starting shell process');
+      printTrace('test $ourTestCount: starting shell process${previewDart2? " in preview-dart-2 mode":""}');
 
+      // [precompiledDillPath] can be set only if [previewDart2] is [true].
+      assert(precompiledDillPath == null || previewDart2);
       // If a kernel file is given, then use that to launch the test.
       // Otherwise create a "listener" dart that invokes actual test.
       String mainDart = precompiledDillPath != null
           ? precompiledDillPath
           : _createListenerDart(finalizers, ourTestCount, testPath, server);
 
-      if (precompiledDillPath == null) {
+      if (previewDart2 && precompiledDillPath == null) {
         // Lazily instantiate compiler so it is built only if it is actually used.
         compiler ??= new _Compiler(trackWidgetCreation);
         mainDart = await compiler.compile(mainDart);
@@ -669,6 +675,10 @@ class _FlutterPlatform extends PlatformPlugin {
   }
 
   String _getBundlePath(List<_Finalizer> finalizers, int ourTestCount) {
+    if (!previewDart2) {
+      return null;
+    }
+
     if (precompiledDillPath != null) {
       return artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath);
     }

packages/flutter_tools/lib/src/test/runner.dart

@@ -4,6 +4,7 @@
 
 import 'dart:async';
 
+import 'package:args/command_runner.dart';
 // ignore: implementation_imports
 import 'package:test/src/executable.dart' as test;
 
@@ -28,10 +29,18 @@ Future<int> runTests(
     bool startPaused = false,
     bool ipv6 = false,
     bool machine = false,
+    bool previewDart2 = false,
     bool trackWidgetCreation = false,
     bool updateGoldens = false,
     TestWatcher watcher,
     }) async {
+  if (trackWidgetCreation && !previewDart2) {
+    throw new UsageException(
+      '--track-widget-creation is valid only when --preview-dart-2 is specified.',
+      null,
+    );
+  }
+
   // Compute the command-line arguments for package:test.
   final List<String> testArgs = <String>[];
   if (!terminal.supportsColor) {
@@ -78,6 +87,7 @@ Future<int> runTests(
     machine: machine,
     startPaused: startPaused,
     serverType: serverType,
+    previewDart2: previewDart2,
     trackWidgetCreation: trackWidgetCreation,
     updateGoldens: updateGoldens,
   );

packages/flutter_tools/lib/src/tester/flutter_tester.dart

@@ -133,11 +133,20 @@ class FlutterTesterDevice extends Device {
       mainPath: mainPath,
       assetDirPath: assetDirPath,
       applicationKernelFilePath: applicationKernelFilePath,
-      precompiledSnapshot: false,
+      precompiledSnapshot: !buildInfo.previewDart2,
+      previewDart2: buildInfo.previewDart2,
       trackWidgetCreation: buildInfo.trackWidgetCreation,
     );
+    if (buildInfo.previewDart2) {
+      mainPath = applicationKernelFilePath;
+    }
+
     command.add('--flutter-assets-dir=$assetDirPath');
-    command.add(applicationKernelFilePath);
+
+    // TODO(scheglov): Either remove the check, or make it fail earlier.
+    if (mainPath != null) {
+      command.add(mainPath);
+    }
 
     try {
       printTrace(command.join(' '));

packages/flutter_tools/test/commands/analyze_continuously_test.dart

@@ -70,10 +70,10 @@ void main() {
     OperatingSystemUtils: () => os
   });
 
-  testUsingContext('Returns no errors when source is error-free', () async {
+  testUsingContext('--preview-dart-2', () async {
     const String contents = "StringBuffer bar = StringBuffer('baz');";
     tempDir.childFile('main.dart').writeAsStringSync(contents);
-    server = new AnalysisServer(dartSdkPath, <String>[tempDir.path]);
+    server = new AnalysisServer(dartSdkPath, <String>[tempDir.path], previewDart2: true);
 
     int errorCount = 0;
     final Future<bool> onDone = server.onAnalyzing.where((bool analyzing) => analyzing == false).first;
@@ -88,6 +88,25 @@ void main() {
   }, overrides: <Type, Generator>{
     OperatingSystemUtils: () => os
   });
+
+  testUsingContext('no --preview-dart-2 shows errors', () async {
+    const String contents = "StringBuffer bar = StringBuffer('baz');";
+    tempDir.childFile('main.dart').writeAsStringSync(contents);
+    server = new AnalysisServer(dartSdkPath, <String>[tempDir.path], previewDart2: false);
+
+    int errorCount = 0;
+    final Future<bool> onDone = server.onAnalyzing.where((bool analyzing) => analyzing == false).first;
+    server.onErrors.listen((FileAnalysisErrors errors) {
+      errorCount += errors.errors.length;
+    });
+
+    await server.start();
+    await onDone;
+
+    expect(errorCount, 1);
+  }, overrides: <Type, Generator>{
+    OperatingSystemUtils: () => os
+  });
 }
 
 void _createSampleProject(Directory directory, { bool brokenCode = false }) {

packages/flutter_tools/test/commands/analyze_once_test.dart

@@ -168,7 +168,7 @@ void bar() {
       }
     });
 
-    testUsingContext('returns no issues when source is error-free', () async {
+    testUsingContext('--preview-dart-2', () async {
       const String contents = '''
 StringBuffer bar = StringBuffer('baz');
 ''';
@@ -179,13 +179,33 @@ StringBuffer bar = StringBuffer('baz');
       try {
         await runCommand(
           command: new AnalyzeCommand(workingDirectory: fs.directory(tempDir)),
-          arguments: <String>['analyze'],
+          arguments: <String>['analyze', '--preview-dart-2'],
           statusTextContains: <String>['No issues found!'],
         );
       } finally {
         tempDir.deleteSync(recursive: true);
       }
     });
+
+    testUsingContext('no --preview-dart-2 shows errors', () async {
+      const String contents = '''
+StringBuffer bar = StringBuffer('baz');
+''';
+
+      final Directory tempDir = fs.systemTempDirectory.createTempSync();
+      tempDir.childFile('main.dart').writeAsStringSync(contents);
+
+      try {
+        await runCommand(
+          command: new AnalyzeCommand(workingDirectory: fs.directory(tempDir)),
+          arguments: <String>['analyze', '--no-preview-dart-2'],
+          statusTextContains: <String>['1 issue found.'],
+          toolExit: true,
+        );
+      } finally {
+        tempDir.deleteSync(recursive: true);
+      }
+    });
   });
 }
 

packages/flutter_tools/test/commands/drive_test.dart

@@ -54,7 +54,7 @@ void main() {
       appStarter = (DriveCommand command) {
         throw 'Unexpected call to appStarter';
       };
-      testRunner = (List<String> testArgs, String observatoryUri) {
+      testRunner = (List<String> testArgs, String observatoryUri, bool previewDart2) {
         throw 'Unexpected call to testRunner';
       };
       appStopper = (DriveCommand command) {
@@ -169,7 +169,7 @@ void main() {
       appStarter = expectAsync1((DriveCommand command) async {
         return new LaunchResult.succeeded();
       });
-      testRunner = expectAsync2((List<String> testArgs, String observatoryUri) async {
+      testRunner = expectAsync3((List<String> testArgs, String observatoryUri, bool previewDart2) async {
         expect(testArgs, <String>[testFile]);
         return null;
       });
@@ -200,7 +200,7 @@ void main() {
       appStarter = expectAsync1((DriveCommand command) async {
         return new LaunchResult.succeeded();
       });
-      testRunner = (List<String> testArgs, String observatoryUri) async {
+      testRunner = (List<String> testArgs, String observatoryUri, bool previewDart2) async {
         throwToolExit(null, exitCode: 123);
       };
       appStopper = expectAsync1((DriveCommand command) async {

packages/flutter_tools/test/ios/xcodeproj_test.dart

@@ -284,10 +284,14 @@ Information about project "Runner":
     testUsingOsxContext('sets ARCHS=armv7 when armv7 local engine is set', () async {
       when(mockArtifacts.getArtifactPath(Artifact.flutterFramework, TargetPlatform.ios, typed(any))).thenReturn('engine');
       when(mockArtifacts.engineOutPath).thenReturn(fs.path.join('out', 'ios_profile_arm'));
-      const BuildInfo buildInfo = const BuildInfo(BuildMode.debug, null, targetPlatform: TargetPlatform.ios);
+      const BuildInfo buildInfo = const BuildInfo(BuildMode.debug, null,
+        previewDart2: true,
+        targetPlatform: TargetPlatform.ios,
+      );
       await updateGeneratedXcodeProperties(
         projectPath: 'path/to/project',
         buildInfo: buildInfo,
+        previewDart2: true,
       );
 
       final File config = fs.file('path/to/project/ios/Flutter/Generated.xcconfig');
@@ -301,12 +305,14 @@ Information about project "Runner":
       when(mockArtifacts.getArtifactPath(Artifact.flutterFramework, TargetPlatform.ios, typed(any))).thenReturn('engine');
       when(mockArtifacts.engineOutPath).thenReturn(fs.path.join('out', 'ios_profile_arm'));
       const BuildInfo buildInfo = const BuildInfo(BuildMode.debug, null,
+        previewDart2: true,
         trackWidgetCreation: true,
         targetPlatform: TargetPlatform.ios,
       );
       await updateGeneratedXcodeProperties(
         projectPath: 'path/to/project',
         buildInfo: buildInfo,
+        previewDart2: true,
       );
 
       final File config = fs.file('path/to/project/ios/Flutter/Generated.xcconfig');
@@ -319,10 +325,14 @@ Information about project "Runner":
     testUsingOsxContext('does not set TRACK_WIDGET_CREATION when trackWidgetCreation is false', () async {
       when(mockArtifacts.getArtifactPath(Artifact.flutterFramework, TargetPlatform.ios, typed(any))).thenReturn('engine');
       when(mockArtifacts.engineOutPath).thenReturn(fs.path.join('out', 'ios_profile_arm'));
-      const BuildInfo buildInfo = const BuildInfo(BuildMode.debug, null, targetPlatform: TargetPlatform.ios);
+      const BuildInfo buildInfo = const BuildInfo(BuildMode.debug, null,
+        previewDart2: true,
+        targetPlatform: TargetPlatform.ios,
+      );
       await updateGeneratedXcodeProperties(
         projectPath: 'path/to/project',
         buildInfo: buildInfo,
+        previewDart2: true,
       );
 
       final File config = fs.file('path/to/project/ios/Flutter/Generated.xcconfig');
@@ -335,10 +345,14 @@ Information about project "Runner":
     testUsingOsxContext('sets ARCHS=armv7 when armv7 local engine is set', () async {
       when(mockArtifacts.getArtifactPath(Artifact.flutterFramework, TargetPlatform.ios, typed(any))).thenReturn('engine');
       when(mockArtifacts.engineOutPath).thenReturn(fs.path.join('out', 'ios_profile'));
-      const BuildInfo buildInfo = const BuildInfo(BuildMode.debug, null, targetPlatform: TargetPlatform.ios);
+      const BuildInfo buildInfo = const BuildInfo(BuildMode.debug, null,
+        previewDart2: true,
+        targetPlatform: TargetPlatform.ios,
+      );
       await updateGeneratedXcodeProperties(
         projectPath: 'path/to/project',
         buildInfo: buildInfo,
+        previewDart2: true,
       );
 
       final File config = fs.file('path/to/project/ios/Flutter/Generated.xcconfig');
@@ -391,6 +405,7 @@ Information about project "Runner":
         projectPath: projectPath,
         buildInfo: buildInfo,
         targetOverride: bundle.defaultMainPath,
+        previewDart2: false,
       );
 
       final String propertiesPath = fs.path.join(projectPath, 'ios', 'Flutter', 'Generated.xcconfig');

packages/flutter_tools/test/resident_runner_test.dart

@@ -44,11 +44,14 @@ class TestRunner extends ResidentRunner {
 
 void main() {
   TestRunner createTestRunner() {
-    // TODO(jacobr): make these tests run with `trackWidgetCreation: true` as
-    // well as the default flags.
+    // TODO(jacobr): make these tests run with `previewDart2: true` and
+    // `trackWidgetCreation: true` as well as the default flags.
+    // Currently the TestRunner is not properly configured to be able to run
+    // with `previewDart2: true` due to missing resources.
     return new TestRunner(
       <FlutterDevice>[new FlutterDevice(
         new MockDevice(),
+        previewDart2: false,
         trackWidgetCreation: false,
       )],
     );

packages/flutter_tools/test/tester/flutter_tester_test.dart

@@ -6,14 +6,11 @@ import 'dart:async';
 
 import 'package:file/file.dart';
 import 'package:file/memory.dart';
-import 'package:flutter_tools/src/artifacts.dart';
 import 'package:flutter_tools/src/base/platform.dart';
 import 'package:flutter_tools/src/build_info.dart';
 import 'package:flutter_tools/src/cache.dart';
-import 'package:flutter_tools/src/compile.dart';
 import 'package:flutter_tools/src/device.dart';
 import 'package:flutter_tools/src/tester/flutter_tester.dart';
-import 'package:mockito/mockito.dart';
 import 'package:process/process.dart';
 import 'package:test/test.dart';
 
@@ -100,8 +97,6 @@ void main() {
       String projectPath;
       String mainPath;
 
-      MockArtifacts mockArtifacts;
-      MockKernelCompiler mockKernelCompiler;
       MockProcessManager mockProcessManager;
       MockProcess mockProcess;
 
@@ -110,8 +105,6 @@ void main() {
         FileSystem: () => fs,
         Cache: () => new Cache(rootOverride: fs.directory(flutterRoot)),
         ProcessManager: () => mockProcessManager,
-        KernelCompiler: () => mockKernelCompiler,
-        Artifacts: () => mockArtifacts,
       };
 
       setUp(() {
@@ -129,13 +122,6 @@ void main() {
         mockProcessManager = new MockProcessManager();
         mockProcessManager.processFactory =
             (List<String> commands) => mockProcess;
-
-        mockArtifacts = new MockArtifacts();
-        final String artifactPath = fs.path.join(flutterRoot, 'artifact');
-        fs.file(artifactPath).createSync(recursive: true);
-        when(mockArtifacts.getArtifactPath(any)).thenReturn(artifactPath);
-
-        mockKernelCompiler = new MockKernelCompiler();
       });
 
       testUsingContext('not debug', () async {
@@ -167,22 +153,6 @@ Hello!
               .codeUnits
         ]));
 
-        when(mockKernelCompiler.compile(
-          sdkRoot: any,
-          incrementalCompilerByteStorePath: any,
-          mainPath: any,
-          outputFilePath: any,
-          depFilePath: any,
-          trackWidgetCreation: any,
-          extraFrontEndOptions: any,
-          fileSystemRoots: any,
-          fileSystemScheme: any,
-          packagesPath: any,
-        )).thenAnswer((_) async {
-          fs.file('$mainPath.dill').createSync(recursive: true);
-          return new CompilerOutput('$mainPath.dill', 0);
-        });
-
         final LaunchResult result = await device.startApp(null,
             mainPath: mainPath,
             debuggingOptions: new DebuggingOptions.enabled(
@@ -195,6 +165,3 @@ Hello!
     });
   });
 }
-
-class MockArtifacts extends Mock implements Artifacts {}
-class MockKernelCompiler extends Mock implements KernelCompiler {}