Add --preview-dart-2 to 'flutter test' (#14135)

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

@@ -68,6 +68,9 @@ class TestCommand extends FlutterCommand {
         negatable: false,
         help: 'Handle machine structured JSON command input\n'
             'and provide output and progress in machine friendly format.');
+    argParser.addFlag('preview-dart-2',
+        hide: !verboseHelp,
+        help: 'Preview Dart 2.0 functionality.');
   }
 
   @override
@@ -206,6 +209,7 @@ class TestCommand extends FlutterCommand {
         startPaused: startPaused,
         ipv6: argResults['ipv6'],
         machine: machine,
+        previewDart2: argResults['preview-dart-2'],
         );
 
     if (collector != null) {

packages/flutter_tools/lib/src/compile.dart

@@ -62,7 +62,8 @@ Future<String> compile(
     bool aot : false,
     bool strongMode : false,
     List<String> extraFrontEndOptions,
-    String incrementalCompilerByteStorePath}) async {
+    String incrementalCompilerByteStorePath,
+    String packagesPath}) async {
   final String frontendServer = artifacts.getArtifactPath(
     Artifact.frontendServerSnapshotForEngineDartSdk
   );
@@ -85,12 +86,12 @@ Future<String> compile(
     command.add('--strong');
   }
   if (incrementalCompilerByteStorePath != null) {
-    command.addAll(<String>[
-      '--incremental',
-      '--byte-store',
-      incrementalCompilerByteStorePath]);
-    fs.directory(incrementalCompilerByteStorePath).createSync(recursive: true);
+    command.add('--incremental');
   }
+  if (packagesPath != null) {
+    command.addAll(<String>['--packages', packagesPath]);
+  }
+
   if (extraFrontEndOptions != null)
     command.addAll(extraFrontEndOptions);
   command.add(mainPath);

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

@@ -5,6 +5,8 @@
 import 'dart:async';
 import 'dart:convert';
 
+import 'package:flutter_tools/src/artifacts.dart';
+import 'package:flutter_tools/src/compile.dart';
 import 'package:meta/meta.dart';
 import 'package:stream_channel/stream_channel.dart';
 
@@ -56,6 +58,7 @@ void installHook({
   bool enableObservatory: false,
   bool machine: false,
   bool startPaused: false,
+  bool previewDart2: false,
   int observatoryPort,
   InternetAddressType serverType: InternetAddressType.IP_V4,
 }) {
@@ -71,6 +74,7 @@ void installHook({
       startPaused: startPaused,
       explicitObservatoryPort: observatoryPort,
       host: _kHosts[serverType],
+      previewDart2: previewDart2,
     ),
   );
 }
@@ -88,6 +92,7 @@ class _FlutterPlatform extends PlatformPlugin {
     this.startPaused,
     this.explicitObservatoryPort,
     this.host,
+    this.previewDart2,
   }) : assert(shellPath != null);
 
   final String shellPath;
@@ -97,6 +102,7 @@ class _FlutterPlatform extends PlatformPlugin {
   final bool startPaused;
   final int explicitObservatoryPort;
   final InternetAddress host;
+  final bool previewDart2;
 
   // Each time loadChannel() is called, we spin up a local WebSocket server,
   // then spin up the engine in a subprocess. We pass the engine a Dart file
@@ -191,14 +197,28 @@ class _FlutterPlatform extends PlatformPlugin {
       ));
 
       // Start the engine subprocess.
-      printTrace('test $ourTestCount: starting shell process');
+      printTrace('test $ourTestCount: starting shell process${previewDart2? " in preview-dart-2 mode":""}');
+
+      final String mainDart = previewDart2
+        ? await compile(
+            sdkRoot: artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath),
+            incrementalCompilerByteStorePath: '' /* not null is enough */,
+            mainPath: listenerFile.path,
+            packagesPath: PackageMap.globalPackagesPath
+          )
+        : listenerFile.path;
+
+      // bundlePath needs to point to a folder with `platform.dill` file.
+      final String bundlePath = previewDart2 ? artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath) : null;
+
       final Process process = await _startProcess(
         shellPath,
-        listenerFile.path,
+        mainDart,
         packages: PackageMap.globalPackagesPath,
         enableObservatory: enableObservatory,
         startPaused: startPaused,
         observatoryPort: explicitObservatoryPort,
+        bundlePath: bundlePath,
       );
       subprocessActive = true;
       finalizers.add(() async {
@@ -466,6 +486,7 @@ void main() {
     String executable,
     String testPath, {
     String packages,
+    String bundlePath,
     bool enableObservatory: false,
     bool startPaused: false,
     int observatoryPort,
@@ -492,6 +513,9 @@ void main() {
     }
     if (host.type == InternetAddressType.IP_V6)
       command.add('--ipv6');
+    if (bundlePath != null) {
+      command.add('--flutter-assets-dir=$bundlePath');
+    }
     command.addAll(<String>[
       '--enable-dart-profiling',
       '--non-interactive',

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

@@ -28,6 +28,7 @@ Future<int> runTests(
     bool startPaused: false,
     bool ipv6: false,
     bool machine: false,
+    bool previewDart2: false,
     TestWatcher watcher,
     }) async {
   // Compute the command-line arguments for package:test.
@@ -75,6 +76,7 @@ Future<int> runTests(
     machine: machine,
     startPaused: startPaused,
     serverType: serverType,
+    previewDart2: previewDart2,
   );
 
   // Make the global packages path absolute.