Support compiling to wasm in build_web_compilers (#3727)

Add `dart2wasm` as a compiler option for `build_web_compilers`.

_test/build.dart2wasm.yaml

@@ -0,0 +1,28 @@
+targets:
+  $default:
+    builders:
+      build_web_compilers:entrypoint:
+        options:
+          compiler: dart2wasm
+          dart2wasm_args:
+          - --enable-asserts
+          - -O0
+        release_options:
+          compiler: dart2wasm
+          dart2wasm_args:
+          - --enable-asserts
+          - -O4
+        generate_for:
+          - web/main.dart
+          - web/sub/main.dart
+          - test/configurable_uri_test.dart
+          - test/configurable_uri_test.dart.browser_test.dart
+          - test/hello_world_test.dart
+          - test/hello_world_test.dart.browser_test.dart
+          - test/hello_world_deferred_test.dart
+          - test/hello_world_deferred_test.dart.browser_test.dart
+          - test/hello_world_custom_html_test.dart
+          - test/hello_world_custom_html_test.dart.browser_test.dart
+          - test/other_test.dart.browser_test.dart
+          - test/sub-dir/subdir_test.dart
+          - test/sub-dir/subdir_test.dart.browser_test.dart

_test/dart_test.yaml

@@ -3,6 +3,12 @@ timeout: 16x
 # package.
 concurrency: 1
 
+tags:
+  integration:
+  # This tag is used for integration tests - we don't need special options at the
+  # moment, but want to avoid warnings from the test runner about using undefined
+  # targets.
+
 override_platforms:
   chrome:
     settings:

_test/lib/app.dart

@@ -2,10 +2,10 @@
 // for details. 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:html';
+import 'package:web/web.dart';
 
 void startApp({String? text}) {
   text ??= 'Hello World!';
-  var component = DivElement()..text = text;
+  var component = HTMLDivElement()..text = text;
   document.body!.append(component);
 }

_test/pkgs/provides_builder/pubspec.yaml

@@ -1,7 +1,7 @@
 name: provides_builder
 resolution: workspace
 environment:
-  sdk: ^3.5.0
+  sdk: ^3.6.0-165.0.dev
 publish_to: none
 
 dependencies:

_test/pubspec.yaml

@@ -1,9 +1,15 @@
 name: _test
 publish_to: none
-resolution: workspace
+# This package can't be part of the workspace because it needs to use the local
+# build_web_compilers, which also isn't part of the workspace. See the top-
+# level pubspec for details.
+#resolution: workspace
 
 environment:
-  sdk: ^3.5.0
+  sdk: ^3.6.0-165.0.dev
+
+dependencies:
+  web: ^1.0.0
 
 dev_dependencies:
   analyzer: any
@@ -15,9 +21,29 @@ dev_dependencies:
   build_runner_core: any
   build_test: any
   build_web_compilers: any
+  dart_flutter_team_lints: ^3.1.0
   io: ^1.0.0
   path: ^1.8.0
   provides_builder:
     path: pkgs/provides_builder/
   test: ^1.16.0
+  test_descriptor: ^2.0.1
   test_process: ^2.0.0
+
+dependency_overrides:
+  build:
+    path: ../build
+  build_config:
+    path: ../build_config
+  build_modules:
+    path: ../build_modules
+  build_resolvers:
+    path: ../build_resolvers
+  build_runner:
+    path: ../build_runner
+  build_runner_core:
+    path: ../build_runner_core
+  build_test:
+    path: ../build_test
+  build_web_compilers:
+    path: ../build_web_compilers

_test/test/common/message_export.dart

@@ -4,4 +4,5 @@
 
 export 'message.dart'
     if (dart.library.io) 'message_io.dart'
-    if (dart.library.html) 'message_html.dart';
+    if (dart.library.html) 'message_html.dart'
+    if (dart.library.js_interop) 'message_js_without_html.dart';

_test/test/common/message_js_without_html.dart

@@ -0,0 +1,5 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+String get message => 'Hello World from WebAssembly!';

_test/test/common/utils.dart

@@ -167,18 +167,22 @@ Future<TestProcess> _runTests(String executable, List<String> scriptArgs,
     List<String>? buildArgs,
     List<String>? testArgs}) async {
   usePrecompiled ??= true;
-  testArgs ??= [];
-  testArgs.addAll(['-p', 'chrome', '-r', 'expanded']);
   if (usePrecompiled) {
     var args = scriptArgs.toList()
       ..add('test')
       ..add('--verbose')
       ..addAll(buildArgs ?? [])
       ..add('--')
-      ..addAll(testArgs);
+      ..addAll([
+        ...?testArgs,
+        '-p',
+        'chrome',
+        '-r',
+        'expanded',
+      ]);
     return TestProcess.start(executable, args);
   } else {
-    var args = ['run', 'test', '--pub-serve', '8081', ...testArgs];
+    var args = ['run', 'test', '--pub-serve', '8081', ...?testArgs];
     return TestProcess.start('dart', args);
   }
 }

_test/test/configurable_uri_test.dart

@@ -6,7 +6,8 @@ import 'package:test/test.dart';
 
 import 'common/message.dart'
     if (dart.library.io) 'common/message_io.dart'
-    if (dart.library.html) 'common/message_html.dart';
+    if (dart.library.html) 'common/message_html.dart'
+    if (dart.library.js_interop) 'common/message_js_without_html.dart';
 
 import 'common/message_export.dart' as exported;
 
@@ -19,7 +20,17 @@ void main() {
     test('exports', () {
       expect(exported.message, contains('Javascript'));
     });
-  }, testOn: 'browser');
+  }, testOn: 'js');
+
+  group('wasm', () {
+    test('imports', () {
+      expect(message, contains('WebAssembly'));
+    });
+
+    test('exports', () {
+      expect(exported.message, contains('WebAssembly'));
+    });
+  }, testOn: 'dart2wasm');
 
   group('vm', () {
     test('imports', () {

_test/test/dart2wasm_integration_test.dart

@@ -0,0 +1,75 @@
+// Copyright (c) 2024, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+@TestOn('vm')
+@Tags(['integration'])
+library;
+
+import 'dart:async';
+
+import 'package:test/test.dart';
+import 'package:test_descriptor/test_descriptor.dart' as d;
+
+import 'common/utils.dart';
+
+// This doesn't actually change anything since we're using precompiled tests,
+// but it gets the compiler selector in tests right.
+const _testArgs = ['-c', 'dart2wasm'];
+
+void main() {
+  group('Can run tests using dart2wasm', () {
+    test('via build.yaml config flag', () async {
+      await expectTestsPass(
+        usePrecompiled: true,
+        buildArgs: [
+          '--config=dart2wasm',
+          '--output=${d.sandbox}',
+        ],
+        testArgs: _testArgs,
+      );
+      await _expectWasCompiledWithDart2Wasm();
+    }, onPlatform: {'windows': const Skip('flaky on windows')});
+
+    test('via --define flag', () async {
+      await expectTestsPass(
+        usePrecompiled: true,
+        buildArgs: [
+          '--define',
+          'build_web_compilers:entrypoint=compiler=dart2wasm',
+          '--define',
+          'build_web_compilers:entrypoint=dart2wasm_args='
+              '["--enable-asserts", "-E--enable-experimental-ffi"]',
+          '--output=${d.sandbox}',
+        ],
+        testArgs: _testArgs,
+      );
+      await _expectWasCompiledWithDart2Wasm();
+    }, onPlatform: {'windows': const Skip('flaky on windows')});
+
+    test('via --release mode', () async {
+      await expectTestsPass(
+        usePrecompiled: true,
+        buildArgs: [
+          '--release',
+          '--config=dart2wasm',
+          '--output=${d.sandbox}',
+        ],
+        testArgs: _testArgs,
+      );
+      await _expectWasCompiledWithDart2Wasm();
+    }, onPlatform: {'windows': const Skip('flaky on windows')});
+  });
+}
+
+Future<void> _expectWasCompiledWithDart2Wasm() async {
+  await d.dir(
+    'test',
+    [
+      d.file(
+        'hello_world_deferred_test.dart.browser_test.wasm',
+        anything,
+      ),
+    ],
+  ).validate();
+}

_test/test/goldens/generated_build_script.dart

@@ -88,9 +88,22 @@ final _builders = <_i1.BuilderApplication>[
     appliesBuilders: const [
       r'build_web_compilers:ddc_modules',
       r'build_web_compilers:dart2js_modules',
+      r'build_web_compilers:dart2wasm_modules',
       r'build_web_compilers:dart_source_cleanup',
     ],
   ),
+  _i1.apply(
+    r'build_web_compilers:dart2wasm_modules',
+    [
+      _i3.dart2wasmMetaModuleBuilder,
+      _i3.dart2wasmMetaModuleCleanBuilder,
+      _i3.dart2wasmModuleBuilder,
+    ],
+    _i1.toNoneByDefault(),
+    isOptional: true,
+    hideOutput: true,
+    appliesBuilders: const [r'build_modules:module_cleanup'],
+  ),
   _i1.apply(
     r'build_web_compilers:dart2js_modules',
     [
@@ -124,7 +137,8 @@ final _builders = <_i1.BuilderApplication>[
       r'dart2js_args': <dynamic>[r'--minify']
     }),
     defaultDevOptions: const _i7.BuilderOptions(<String, dynamic>{
-      r'dart2js_args': <dynamic>[r'--enable-asserts']
+      r'dart2wasm_args': <dynamic>[r'--enable-asserts'],
+      r'dart2js_args': <dynamic>[r'--enable-asserts'],
     }),
     defaultReleaseOptions:
         const _i7.BuilderOptions(<String, dynamic>{r'compiler': r'dart2js'}),

_test/test/hello_world_custom_html_test.dart

@@ -5,9 +5,8 @@
 @TestOn('browser')
 library;
 
-import 'dart:html';
-
 import 'package:test/test.dart';
+import 'package:web/web.dart';
 
 void main() {
   test('can use custom html', () {

_test/test/hello_world_deferred_test.dart

@@ -5,22 +5,23 @@
 @TestOn('browser')
 library;
 
-import 'dart:html';
+import 'dart:js_interop';
 
 import 'package:_test/app.dart';
 import 'package:test/test.dart';
+import 'package:web/web.dart';
 
 import 'common/message.dart' deferred as m;
 
 void main() {
   setUp(startApp);
 
   tearDown(() {
-    document.body!.innerHtml = '';
+    document.body!.innerHTML = ''.toJS;
   });
 
   test('hello world', () async {
     await m.loadLibrary();
-    expect(document.body?.text, contains(m.message));
+    expect(document.body?.innerText, contains(m.message));
   });
 }

_test/test/hello_world_test.dart

@@ -5,10 +5,11 @@
 @TestOn('browser')
 library;
 
-import 'dart:html';
+import 'dart:js_interop';
 
 import 'package:_test/app.dart';
 import 'package:test/test.dart';
+import 'package:web/web.dart';
 
 //import_anchor
 
@@ -18,11 +19,11 @@ void main() {
   setUp(startApp);
 
   tearDown(() {
-    document.body!.innerHtml = '';
+    document.body!.innerHTML = ''.toJS;
   });
 
   test('hello world', () {
-    expect(document.body!.text, contains(message));
+    expect(document.body!.innerText, contains(message));
   });
 
   test('failing test', skip: 'Expected failure', () {

build_web_compilers/CHANGELOG.md

@@ -1,7 +1,9 @@
 ## 4.0.12-wip
 
-- Bump the min sdk to 3.5.0.
 - Account for dartdevc snapshot in the Dart SDK changing to an AOT snapshot.
+- Support compiling to WebAssembly by using `dart2wasm` as a value for the
+  compiler option.
+- Bump the min sdk to 3.6.0-165.0.dev.
 
 ## 4.0.11