[null-safety] add integration tests for sound null safety modes, add support for sound null safety in dart2js (#67171)

Add integration tests to verify that ddc and dart2js can be built and run in sound mode. Updates dart2js compilation to insert a language version comment into the generated entrypoint if necessary.

dart-lang/sdk#42253

dev/bots/test.dart

@@ -765,6 +765,16 @@ Future<void> _runWebIntegrationTests() async {
       '--dart-define=test.valueB=Value',
     ]
   );
+  await _runWebDebugTest('lib/sound_mode.dart', additionalArguments: <String>[
+    '--enable-experiment',
+    'non-nullable',
+    '--sound-null-safety',
+  ]);
+  await _runWebReleaseTest('lib/sound_mode.dart', additionalArguments: <String>[
+    '--enable-experiment',
+    'non-nullable',
+    '--sound-null-safety',
+  ]);
 }
 
 Future<void> _runWebStackTraceTest(String buildMode) async {

dev/integration_tests/web/analysis_options.yaml

@@ -3,3 +3,4 @@
 analyzer:
   exclude:
     - lib/null_safe_main.dart
+    - lib/sound_mode.dart

dev/integration_tests/web/lib/sound_mode.dart

@@ -0,0 +1,24 @@
+// 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=2.10
+
+import 'dart:html' as html;
+
+// Verify that web applications can be run in sound mode.
+void main() {
+  const isWeak = <int?>[] is List<int>;
+  String output;
+  if (isWeak) {
+    output = '--- TEST FAILED ---';
+  } else {
+    output = '--- TEST SUCCEEDED ---';
+  }
+  print(output);
+  html.HttpRequest.request(
+    '/test-result',
+    method: 'POST',
+    sendData: '$output',
+  );
+}

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

@@ -12,6 +12,7 @@ import '../../artifacts.dart';
 import '../../base/file_system.dart';
 import '../../base/io.dart';
 import '../../build_info.dart';
+import '../../dart/language_version.dart';
 import '../../dart/package_map.dart';
 import '../../globals.dart' as globals;
 import '../../project.dart';
@@ -94,6 +95,11 @@ class WebEntrypointTarget extends Target {
       environment.fileSystem.file(packageFile),
       logger: environment.logger,
     );
+    final FlutterProject flutterProject = FlutterProject.current();
+    final String languageVersion = determineLanguageVersion(
+      environment.fileSystem.file(targetFile),
+      packageConfig[flutterProject.manifest.appName],
+    ) ?? '';
 
     // Use the PackageConfig to find the correct package-scheme import path
     // for the user application. If the application has a mix of package-scheme
@@ -117,6 +123,8 @@ class WebEntrypointTarget extends Target {
       final String generatedImport = packageConfig.toPackageUri(generatedUri)?.toString()
         ?? generatedUri.toString();
       contents = '''
+$languageVersion
+
 import 'dart:ui' as ui;
 
 import 'package:flutter_web_plugins/flutter_web_plugins.dart';
@@ -134,6 +142,8 @@ Future<void> main() async {
 ''';
     } else {
       contents = '''
+$languageVersion
+
 import 'dart:ui' as ui;
 
 import '$mainImport' as entrypoint;

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

@@ -72,6 +72,10 @@ void main() {
   });
 
   test('WebEntrypointTarget generates an entrypoint with plugins and init platform', () => testbed.run(() async {
+    final File mainFile = globals.fs.file(globals.fs.path.join('foo', 'lib', 'main.dart'))
+      ..createSync(recursive: true)
+      ..writeAsStringSync('void main() {}');
+    environment.defines[kTargetFile] = mainFile.path;
     environment.defines[kHasWebPlugins] = 'true';
     environment.defines[kInitializePlatform] = 'true';
     await const WebEntrypointTarget().build(environment);
@@ -144,7 +148,10 @@ void main() {
   }));
 
   test('WebEntrypointTarget generates an entrypoint for a file outside of main', () => testbed.run(() async {
-    environment.defines[kTargetFile] = globals.fs.path.join('other', 'lib', 'main.dart');
+    final File mainFile = globals.fs.file(globals.fs.path.join('other', 'lib', 'main.dart'))
+      ..createSync(recursive: true)
+      ..writeAsStringSync('void main() {}');
+    environment.defines[kTargetFile] = mainFile.path;
     await const WebEntrypointTarget().build(environment);
 
     final String generated = environment.buildDir.childFile('main.dart').readAsStringSync();
@@ -154,7 +161,10 @@ void main() {
   }));
 
   test('WebEntrypointTarget generates a plugin registrant for a file outside of main', () => testbed.run(() async {
-    environment.defines[kTargetFile] = globals.fs.path.join('other', 'lib', 'main.dart');
+    final File mainFile = globals.fs.file(globals.fs.path.join('other', 'lib', 'main.dart'))
+      ..createSync(recursive: true)
+      ..writeAsStringSync('void main() {}');
+    environment.defines[kTargetFile] = mainFile.path;
     environment.defines[kHasWebPlugins] = 'true';
     await const WebEntrypointTarget().build(environment);
 
@@ -167,6 +177,11 @@ void main() {
 
 
   test('WebEntrypointTarget generates an entrypoint with plugins and init platform on windows', () => testbed.run(() async {
+    final File mainFile = globals.fs.file(globals.fs.path.join('foo', 'lib', 'main.dart'))
+      ..createSync(recursive: true)
+      ..writeAsStringSync('void main() {}');
+    environment.defines[kTargetFile] = mainFile.path;
+
     environment.defines[kHasWebPlugins] = 'true';
     environment.defines[kInitializePlatform] = 'true';
     await const WebEntrypointTarget().build(environment);
@@ -190,6 +205,10 @@ void main() {
   }));
 
   test('WebEntrypointTarget generates an entrypoint without plugins and init platform', () => testbed.run(() async {
+    final File mainFile = globals.fs.file(globals.fs.path.join('foo', 'lib', 'main.dart'))
+      ..createSync(recursive: true)
+      ..writeAsStringSync('void main() {}');
+    environment.defines[kTargetFile] = mainFile.path;
     environment.defines[kHasWebPlugins] = 'false';
     environment.defines[kInitializePlatform] = 'true';
     await const WebEntrypointTarget().build(environment);
@@ -208,6 +227,10 @@ void main() {
   }));
 
   test('WebEntrypointTarget generates an entrypoint with plugins and without init platform', () => testbed.run(() async {
+    final File mainFile = globals.fs.file(globals.fs.path.join('foo', 'lib', 'main.dart'))
+      ..createSync(recursive: true)
+      ..writeAsStringSync('void main() {}');
+    environment.defines[kTargetFile] = mainFile.path;
     environment.defines[kHasWebPlugins] = 'true';
     environment.defines[kInitializePlatform] = 'false';
     await const WebEntrypointTarget().build(environment);
@@ -225,7 +248,39 @@ void main() {
     expect(generated, contains('entrypoint.main();'));
   }));
 
+  test('WebEntrypointTarget generates an entrypoint with a language version', () => testbed.run(() async {
+    final File mainFile = globals.fs.file(globals.fs.path.join('foo', 'lib', 'main.dart'))
+      ..createSync(recursive: true)
+      ..writeAsStringSync('// @dart=2.8\nvoid main() {}');
+    environment.defines[kTargetFile] = mainFile.path;
+    await const WebEntrypointTarget().build(environment);
+
+    final String generated = environment.buildDir.childFile('main.dart').readAsStringSync();
+
+    // Language version
+    expect(generated, contains('// @dart=2.8'));
+  }));
+
+  test('WebEntrypointTarget generates an entrypoint with a language version from a package config', () => testbed.run(() async {
+    final File mainFile = globals.fs.file(globals.fs.path.join('foo', 'lib', 'main.dart'))
+      ..createSync(recursive: true)
+      ..writeAsStringSync('void main() {}');
+    globals.fs.file(globals.fs.path.join('pubspec.yaml'))
+      .writeAsStringSync('name: foo\n');
+    environment.defines[kTargetFile] = mainFile.path;
+    await const WebEntrypointTarget().build(environment);
+
+    final String generated = environment.buildDir.childFile('main.dart').readAsStringSync();
+
+    // Language version
+    expect(generated, contains('// @dart = 2.7'));
+  }));
+
   test('WebEntrypointTarget generates an entrypoint without plugins and without init platform', () => testbed.run(() async {
+    final File mainFile = globals.fs.file(globals.fs.path.join('foo', 'lib', 'main.dart'))
+      ..createSync(recursive: true)
+      ..writeAsStringSync('void main() {}');
+    environment.defines[kTargetFile] = mainFile.path;
     environment.defines[kHasWebPlugins] = 'false';
     environment.defines[kInitializePlatform] = 'false';
     await const WebEntrypointTarget().build(environment);