It's time to #deleteDart1 (again) (#18316)

* It's time to #deleteDart1 (#18293)

Eliminates support for Dart 1 in flutter_tools, and drops our Dart 1
benchmarks. All commands now run in Dart 1 mode only.

Eliminates --preview-dart-2 / --no-preview-dart-2 support.

* Fix indentation, remove no longer necessary .toList()

* Only push udpated kernel if >0 invalidated srcs

dev/bots/test.dart

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

dev/devicelab/bin/tasks/gradle_plugin_test.dart

@@ -32,14 +32,6 @@ 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

@@ -1,12 +0,0 @@
-// 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

@@ -1,14 +0,0 @@
-// 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({ bool isPreviewDart2 = true }) {
+TaskFunction createHotModeTest() {
   return () async {
     final Device device = await devices.workingDevice;
     await device.unlock();
@@ -25,10 +25,6 @@ TaskFunction createHotModeTest({ bool isPreviewDart2 = true }) {
     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;
@@ -92,8 +88,8 @@ TaskFunction createHotModeTest({ bool isPreviewDart2 = true }) {
         }
         benchmarkFile.deleteSync();
 
-        // start `flutter run` again to make sure it loads from the previous state
+        // start `flutter run` again to make sure it loads from the previous
-        // (in case of --preview-dart-2 frontend loads up from previously generated kernel files).
+        // state; 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, {bool previewDart2 = true}) async {
+    Future<Map<String, double>> _runMicrobench(String benchmarkPath) async {
       Future<Map<String, double>> _run() async {
         print('Running $benchmarkPath');
         final Directory appDir = dir(
@@ -38,10 +38,6 @@ 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(
@@ -61,26 +57,6 @@ 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

@@ -205,23 +205,13 @@ 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 Map<String, dynamic> _suffix(Map<String, dynamic> map, String suffix) {
+  static Future<Map<String, dynamic>> _compileAot() async {
-    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();
@@ -240,10 +230,6 @@ 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();
@@ -258,15 +244,11 @@ class CompileTest {
     return metrics;
   }
 
-  static Future<Map<String, dynamic>> _compileApp({ bool previewDart2 = true }) async {
+  static Future<Map<String, dynamic>> _compileApp() 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:
@@ -299,14 +281,10 @@ class CompileTest {
     };
   }
 
-  static Future<Map<String, dynamic>> _compileDebug({ bool previewDart2 = true }) async {
+  static Future<Map<String, dynamic>> _compileDebug() 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

@@ -154,21 +154,6 @@ 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

@@ -102,13 +102,6 @@ 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"
@@ -127,7 +120,6 @@ BuildApp() {
       --${build_mode}                                                       \
       --ios-arch="${archs}"                                                 \
       ${local_engine_flag}                                                  \
-      ${preview_dart_2_flag}                                                \
       ${track_widget_creation_flag}
 
     if [[ $? -ne 0 ]]; then
@@ -167,12 +159,10 @@ 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

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

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

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

@@ -64,70 +64,6 @@ 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({
@@ -136,7 +72,6 @@ class AOTSnapshotter {
     @required String mainPath,
     @required String packagesPath,
     @required String outputPath,
-    @required bool previewDart2,
     @required bool buildSharedLibrary,
     IOSArch iosArch,
     List<String> extraGenSnapshotOptions = const <String>[],
@@ -192,12 +127,10 @@ class AOTSnapshotter {
       '--embedder_entry_points_manifest=$ioEntryPoints',
       '--dependencies=$depfilePath',
     ];
-    if (previewDart2) {
+    genSnapshotArgs.addAll(<String>[
-      genSnapshotArgs.addAll(<String>[
+      '--reify-generic-functions',
-        '--reify-generic-functions',
+      '--strong',
-        '--strong',
+    ]);
-      ]);
-    }
     if (extraGenSnapshotOptions != null && extraGenSnapshotOptions.isNotEmpty) {
       printTrace('Extra gen_snapshot options: $extraGenSnapshotOptions');
       genSnapshotArgs.addAll(extraGenSnapshotOptions);
@@ -252,7 +185,6 @@ 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

@@ -11,7 +11,6 @@ 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,
@@ -33,9 +32,6 @@ 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;
 
@@ -93,7 +89,6 @@ 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

@@ -6,7 +6,6 @@ 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';
@@ -24,7 +23,6 @@ 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';
@@ -33,13 +31,11 @@ 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,
@@ -47,32 +43,13 @@ 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 && previewDart2) {
+  if (!precompiledSnapshot) {
     if ((extraFrontEndOptions != null) && extraFrontEndOptions.isNotEmpty)
       printTrace('Extra front-end options: $extraFrontEndOptions');
     ensureDirectoryExists(applicationKernelFilePath);
@@ -109,7 +86,6 @@ Future<void> build({
   await assemble(
     assetBundle: assets,
     kernelContent: kernelContent,
-    snapshotFile: snapshotFile,
     privateKeyPath: privateKeyPath,
     assetDirPath: assetDirPath,
   );
@@ -143,7 +119,6 @@ Future<AssetBundle> buildAssets({
 Future<void> assemble({
   AssetBundle assetBundle,
   DevFSContent kernelContent,
-  File snapshotFile,
   File dylibFile,
   String privateKeyPath = defaultPrivateKeyPath,
   String assetDirPath,
@@ -152,21 +127,16 @@ 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

@@ -26,8 +26,6 @@ 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 '
@@ -87,7 +85,6 @@ class AnalyzeCommand extends FlutterCommand {
         argResults,
         runner.getRepoRoots(),
         runner.getRepoPackages(),
-        previewDart2: argResults['preview-dart-2'],
       ).analyze();
     } else {
       return new AnalyzeOnce(
@@ -95,7 +92,6 @@ 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

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

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

@@ -24,7 +24,6 @@ class AnalyzeOnce extends AnalyzeBase {
     this.repoRoots,
     this.repoPackages, {
     this.workingDirectory,
-    this.previewDart2 = false,
   }) : super(argResults);
 
   final List<String> repoRoots;
@@ -33,8 +32,6 @@ 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 =
@@ -91,7 +88,6 @@ 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

@@ -28,11 +28,6 @@ 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,
@@ -79,23 +74,20 @@ 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, if Dart 2.
+      // Compile to kernel.
-      if (previewDart2) {
+      mainPath = await snapshotter.compileKernel(
-        mainPath = await snapshotter.compileKernel(
+        platform: platform,
-          platform: platform,
+        buildMode: buildMode,
-          buildMode: buildMode,
+        mainPath: mainPath,
-          mainPath: mainPath,
+        outputPath: outputPath,
-          outputPath: outputPath,
+        extraFrontEndOptions: argResults[FlutterOptions.kExtraFrontEndOptions],
-          extraFrontEndOptions: argResults[FlutterOptions.kExtraFrontEndOptions],
+      );
-        );
+      if (mainPath == null) {
-        if (mainPath == null) {
+        printError('Compiler terminated unexpectedly.');
-          printError('Compiler terminated unexpectedly.');
+        return;
-          return;
-        }
       }
 
       // Build AOT snapshot.
@@ -116,7 +108,6 @@ class BuildAotCommand extends BuildSubCommand {
             mainPath: mainPath,
             packagesPath: PackageMap.globalPackagesPath,
             outputPath: outputPath,
-            previewDart2: previewDart2,
             buildSharedLibrary: false,
             extraGenSnapshotOptions: argResults[FlutterOptions.kExtraGenSnapshotOptions],
           ).then((int buildExitCode) {
@@ -143,7 +134,6 @@ 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

@@ -17,11 +17,6 @@ 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

@@ -19,14 +19,8 @@ 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.',
@@ -72,12 +66,10 @@ 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'],