[flutter_tools] support --enable-experiment in flutter test (#55564)

Support --enable-experiment in flutter test (for flutter_tester). Required minor change for null safety.

dev/bots/test.dart

@@ -480,6 +480,9 @@ Future<void> _runFrameworkTests() async {
     await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_localizations'), tableData: bigqueryApi?.tabledata);
     await _runFlutterTest(path.join(flutterRoot, 'packages', 'flutter_test'), tableData: bigqueryApi?.tabledata);
     await _runFlutterTest(path.join(flutterRoot, 'packages', 'fuchsia_remote_debug_protocol'), tableData: bigqueryApi?.tabledata);
+    await _runFlutterTest(path.join(flutterRoot, 'dev', 'integration_tests', 'non_nullable'),
+      options: <String>['--enable-experiment=non-nullable'],
+    );
     await _runFlutterTest(
       path.join(flutterRoot, 'dev', 'tracing_tests'),
       options: <String>['--enable-vmservice'],

dev/integration_tests/non_nullable/analysis_options.yaml

@@ -3,3 +3,4 @@
 analyzer:
   exclude:
     - lib/main.dart
+    - test/test_test.dart

dev/integration_tests/non_nullable/test/test_test.dart

@@ -0,0 +1,14 @@
+// Copyright 2014 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// @dart=2.9
+import 'package:flutter_test/flutter_test.dart';
+
+String? x;
+
+void main() {
+  testWidgets('trivial', (WidgetTester tester) async {
+    expect(true, true);
+  });
+}

packages/flutter_tools/bin/fuchsia_tester.dart

@@ -155,6 +155,7 @@ Future<void> run(List<String> args) async {
       concurrency: math.max(1, globals.platform.numberOfProcessors - 2),
       icudtlPath: globals.fs.path.absolute(argResults[_kOptionIcudtl] as String),
       coverageDirectory: coverageDirectory,
+      dartExperiments: <String>[],
     );
 
     if (collector != null) {

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

@@ -129,6 +129,7 @@ class TestCommand extends FlutterCommand {
               'The vmservice will be enabled no matter what in those cases.'
       );
     usesTrackWidgetCreation(verboseHelp: verboseHelp);
+    addEnableExperimentation(hide: !verboseHelp);
   }
 
   /// The interface for starting and configuring the tester.
@@ -171,6 +172,7 @@ class TestCommand extends FlutterCommand {
     final String tags = stringArg('tags');
     final String excludeTags = stringArg('exclude-tags');
     final FlutterProject flutterProject = FlutterProject.current();
+    final List<String> dartExperiments = stringsArg(FlutterOptions.kEnableExperiment);
 
     if (buildTestAssets && flutterProject.manifest.assets.isNotEmpty) {
       await _buildTestAsset();
@@ -276,6 +278,7 @@ class TestCommand extends FlutterCommand {
       flutterProject: flutterProject,
       web: stringArg('platform') == 'chrome',
       randomSeed: stringArg('test-randomize-ordering-seed'),
+      dartExperiments: dartExperiments,
     );
 
     if (collector != null) {

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

@@ -87,6 +87,7 @@ FlutterPlatform installHook({
   FlutterProject flutterProject,
   String icudtlPath,
   PlatformPluginRegistration platformPluginRegistration,
+  @required List<String> dartExperiments,
 }) {
   assert(testWrapper != null);
   assert(enableObservatory || (!startPaused && observatoryPort == null));
@@ -119,6 +120,7 @@ FlutterPlatform installHook({
     projectRootDirectory: projectRootDirectory,
     flutterProject: flutterProject,
     icudtlPath: icudtlPath,
+    dartExperiments: dartExperiments,
   );
   platformPluginRegistration(platform);
   return platform;
@@ -144,6 +146,7 @@ String generateTestBootstrap({
   @required InternetAddress host,
   File testConfigFile,
   bool updateGoldens = false,
+  @required bool nullSafety,
 }) {
   assert(testUrl != null);
   assert(host != null);
@@ -173,11 +176,15 @@ import '$testUrl' as test;
 import '${Uri.file(testConfigFile.path)}' as test_config;
 ''');
   }
+  // This type is sensitive to the non-nullable experiment.
+  final String beforeLoadTypedef = nullSafety
+    ? 'Future<dynamic> Function()?'
+    : 'Future<dynamic> Function()';
   buffer.write('''
 
 /// Returns a serialized test suite.
 StreamChannel<dynamic> serializeSuite(Function getMain(),
-    {bool hidePrints = true, Future<dynamic> beforeLoad()}) {
+    {bool hidePrints = true, $beforeLoadTypedef beforeLoad}) {
   return RemoteListener.start(getMain,
       hidePrints: hidePrints, beforeLoad: beforeLoad);
 }
@@ -259,6 +266,7 @@ class FlutterPlatform extends PlatformPlugin {
     this.projectRootDirectory,
     this.flutterProject,
     this.icudtlPath,
+    @required this.dartExperiments,
   }) : assert(shellPath != null);
 
   final String shellPath;
@@ -279,6 +287,7 @@ class FlutterPlatform extends PlatformPlugin {
   final Uri projectRootDirectory;
   final FlutterProject flutterProject;
   final String icudtlPath;
+  final List<String> dartExperiments;
 
   Directory fontsDirectory;
 
@@ -447,7 +456,7 @@ class FlutterPlatform extends PlatformPlugin {
 
       if (precompiledDillPath == null && precompiledDillFiles == null) {
         // Lazily instantiate compiler so it is built only if it is actually used.
-        compiler ??= TestCompiler(buildMode, trackWidgetCreation, flutterProject);
+        compiler ??= TestCompiler(buildMode, trackWidgetCreation, flutterProject, dartExperiments);
         mainDart = await compiler.compile(globals.fs.file(mainDart).uri);
 
         if (mainDart == null) {
@@ -739,6 +748,7 @@ class FlutterPlatform extends PlatformPlugin {
       testConfigFile: findTestConfigFile(globals.fs.file(testUrl)),
       host: host,
       updateGoldens: updateGoldens,
+      nullSafety: dartExperiments.contains('non-nullable'),
     );
   }
 

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

@@ -75,7 +75,7 @@ class FlutterWebPlatform extends PlatformPlugin {
 
     _testGoldenComparator = TestGoldenComparator(
       shellPath,
-      () => TestCompiler(BuildMode.debug, false, flutterProject),
+      () => TestCompiler(BuildMode.debug, false, flutterProject, <String>[]),
     );
   }
 

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

@@ -51,6 +51,7 @@ abstract class FlutterTestRunner {
     Directory coverageDirectory,
     bool web = false,
     String randomSeed,
+    @required List<String> dartExperiments,
   });
 }
 
@@ -84,6 +85,7 @@ class _FlutterTestRunnerImpl implements FlutterTestRunner {
     Directory coverageDirectory,
     bool web = false,
     String randomSeed,
+    @required List<String> dartExperiments,
   }) async {
     // Configure package:test to use the Flutter engine for child processes.
     final String shellPath = globals.artifacts.getArtifactPath(Artifact.flutterTester);
@@ -175,6 +177,7 @@ class _FlutterTestRunnerImpl implements FlutterTestRunner {
       projectRootDirectory: globals.fs.currentDirectory.uri,
       flutterProject: flutterProject,
       icudtlPath: icudtlPath,
+      dartExperiments: dartExperiments,
     );
 
     // Make the global packages path absolute.

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

@@ -42,6 +42,7 @@ class TestCompiler {
     this.buildMode,
     this.trackWidgetCreation,
     this.flutterProject,
+    this.dartExperiments,
   ) : testFilePath = getKernelPathForTransformerOptions(
         globals.fs.path.join(flutterProject.directory.path, getBuildDirectory(), 'testfile.dill'),
         trackWidgetCreation: trackWidgetCreation,
@@ -65,6 +66,7 @@ class TestCompiler {
   final BuildMode buildMode;
   final bool trackWidgetCreation;
   final String testFilePath;
+  final List<String> dartExperiments;
 
 
   ResidentCompiler compiler;
@@ -104,6 +106,7 @@ class TestCompiler {
       unsafePackageSerialization: false,
       dartDefines: const <String>[],
       packagesPath: globalPackagesPath,
+      experimentalFlags: dartExperiments,
     );
     if (flutterProject.hasBuilders) {
       return CodeGeneratingResidentCompiler.create(

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

@@ -184,6 +184,7 @@ class FakeFlutterTestRunner implements FlutterTestRunner {
     Directory coverageDirectory,
     bool web = false,
     String randomSeed,
+    @override List<String> dartExperiments,
   }) async {
     lastEnableObservatoryValue = enableObservatory;
     return exitCode;

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

@@ -17,15 +17,29 @@ import '../src/context.dart';
 
 void main() {
   group('FlutterPlatform', () {
-    testUsingContext('ensureConfiguration throws an error if an explicitObservatoryPort is specified and more than one test file', () async {
-      final FlutterPlatform flutterPlatform = FlutterPlatform(buildMode: BuildMode.debug, shellPath: '/', explicitObservatoryPort: 1234);
+    testUsingContext('ensureConfiguration throws an error if an '
+      'explicitObservatoryPort is specified and more than one test file', () async {
+      final FlutterPlatform flutterPlatform = FlutterPlatform(
+        buildMode: BuildMode.debug,
+        shellPath: '/',
+        explicitObservatoryPort: 1234,
+        dartExperiments: <String>[],
+      );
       flutterPlatform.loadChannel('test1.dart', MockSuitePlatform());
+
       expect(() => flutterPlatform.loadChannel('test2.dart', MockSuitePlatform()), throwsToolExit());
     });
 
-    testUsingContext('ensureConfiguration throws an error if a precompiled entrypoint is specified and more that one test file', () {
-      final FlutterPlatform flutterPlatform = FlutterPlatform(buildMode: BuildMode.debug, shellPath: '/', precompiledDillPath: 'example.dill');
+    testUsingContext('ensureConfiguration throws an error if a precompiled '
+      'entrypoint is specified and more that one test file', () {
+      final FlutterPlatform flutterPlatform = FlutterPlatform(
+        buildMode: BuildMode.debug,
+        shellPath: '/',
+        precompiledDillPath: 'example.dill',
+        dartExperiments: <String>[],
+      );
       flutterPlatform.loadChannel('test1.dart', MockSuitePlatform());
+
       expect(() => flutterPlatform.loadChannel('test2.dart', MockSuitePlatform()), throwsToolExit());
     });
 
@@ -99,6 +113,7 @@ void main() {
         shellPath: 'abc',
         enableObservatory: false,
         startPaused: true,
+        dartExperiments: <String>[],
       ), throwsAssertionError);
 
       expect(() => installHook(
@@ -107,6 +122,7 @@ void main() {
         enableObservatory: false,
         startPaused: false,
         observatoryPort: 123,
+        dartExperiments: <String>[],
       ), throwsAssertionError);
 
       FlutterPlatform capturedPlatform;
@@ -127,6 +143,7 @@ void main() {
         observatoryPort: 200,
         serverType: InternetAddressType.IPv6,
         icudtlPath: 'ghi',
+        dartExperiments: <String>[],
         platformPluginRegistration: (FlutterPlatform platform) {
           capturedPlatform = platform;
         });
@@ -175,6 +192,7 @@ class TestFlutterPlatform extends FlutterPlatform {
     startPaused: false,
     enableObservatory: false,
     buildTestAssets: false,
+    dartExperiments: <String>[],
   );
 
   @override

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

@@ -96,7 +96,7 @@ class FakeTestCompiler extends TestCompiler {
     bool trackWidgetCreation,
     FlutterProject flutterProject,
     this.residentCompiler,
-  ) : super(buildMode, trackWidgetCreation, flutterProject);
+  ) : super(buildMode, trackWidgetCreation, flutterProject, <String>[]);
 
   final MockResidentCompiler residentCompiler;