Support flutter build web --wasm (#117075)

* Work in progress. * Some fixes to the command line. * Bootstrapping works. * Change kickoff order to maximize concurrency. * Fix analyzer errors and formatting issues. * Fix doc comment. * Added unit tests for some of the web targets. * Format issue. * Add an integration test that builds an app to wasm. * Add a todo for depfiles. * Formatting. * Apparently the license header needs to say 2014. * `file://` URIs confuse dart2wasm on Windows. Just use absolute paths. * Update unit tests to match new path passing. * Have a distinct build directory for wasm, and fixes for some upstream changes.
2024-10-13 11:42:54 +00:00 · 2022-12-19 12:09:02 -08:00 · 2022-12-19 12:09:02 -08:00 · 9f2c5d8e21
parent 70f391db77
commit 9f2c5d8e21
9 changed files with 322 additions and 61 deletions
--- a/packages/flutter_tools/lib/src/artifacts.dart
+++ b/packages/flutter_tools/lib/src/artifacts.dart
@ -34,10 +34,14 @@ enum Artifact {
  engineDartSdkPath,
  /// The dart binary used to execute any of the required snapshots.
  engineDartBinary,
+  /// The dart binary for running aot snapshots
+  engineDartAotRuntime,
  /// The snapshot of frontend_server compiler.
  frontendServerSnapshotForEngineDartSdk,
  /// The dart snapshot of the dart2js compiler.
  dart2jsSnapshot,
+  /// The dart snapshot of the dart2wasm compiler.
+  dart2wasmSnapshot,

  /// The root of the Linux desktop sources.
  linuxDesktopPath,
@ -168,8 +172,12 @@ String? _artifactToFileName(Artifact artifact, Platform hostPlatform, [ BuildMod
      return 'dart-sdk';
    case Artifact.engineDartBinary:
      return 'dart$exe';
+    case Artifact.engineDartAotRuntime:
+      return 'dartaotruntime$exe';
    case Artifact.dart2jsSnapshot:
      return 'dart2js.dart.snapshot';
+    case Artifact.dart2wasmSnapshot:
+      return 'dart2wasm_product.snapshot';
    case Artifact.frontendServerSnapshotForEngineDartSdk:
      return 'frontend_server.dart.snapshot';
    case Artifact.linuxDesktopPath:
@ -488,7 +496,9 @@ class CachedArtifacts implements Artifacts {
        return _fileSystem.path.join(engineDir, hostPlatform, _artifactToFileName(artifact, _platform));
      case Artifact.engineDartSdkPath:
      case Artifact.engineDartBinary:
+      case Artifact.engineDartAotRuntime:
      case Artifact.dart2jsSnapshot:
+      case Artifact.dart2wasmSnapshot:
      case Artifact.frontendServerSnapshotForEngineDartSdk:
      case Artifact.constFinder:
      case Artifact.flutterFramework:
@ -525,7 +535,9 @@ class CachedArtifacts implements Artifacts {
        return _getIosEngineArtifactPath(engineDir, environmentType, _fileSystem, _platform);
      case Artifact.engineDartSdkPath:
      case Artifact.engineDartBinary:
+      case Artifact.engineDartAotRuntime:
      case Artifact.dart2jsSnapshot:
+      case Artifact.dart2wasmSnapshot:
      case Artifact.frontendServerSnapshotForEngineDartSdk:
      case Artifact.constFinder:
      case Artifact.flutterMacOSFramework:
@ -580,7 +592,9 @@ class CachedArtifacts implements Artifacts {
      case Artifact.fontSubset:
      case Artifact.engineDartSdkPath:
      case Artifact.engineDartBinary:
+      case Artifact.engineDartAotRuntime:
      case Artifact.dart2jsSnapshot:
+      case Artifact.dart2wasmSnapshot:
      case Artifact.frontendServerSnapshotForEngineDartSdk:
      case Artifact.icuData:
      case Artifact.isolateSnapshotData:
@ -613,6 +627,7 @@ class CachedArtifacts implements Artifacts {
        // android_arm in profile mode because it is available on all supported host platforms.
        return _getAndroidArtifactPath(artifact, TargetPlatform.android_arm, BuildMode.profile);
      case Artifact.dart2jsSnapshot:
+      case Artifact.dart2wasmSnapshot:
      case Artifact.frontendServerSnapshotForEngineDartSdk:
        return _fileSystem.path.join(
          _dartSdkPath(_cache), 'bin', 'snapshots',
@ -634,6 +649,7 @@ class CachedArtifacts implements Artifacts {
      case Artifact.engineDartSdkPath:
        return _dartSdkPath(_cache);
      case Artifact.engineDartBinary:
+      case Artifact.engineDartAotRuntime:
        return _fileSystem.path.join(_dartSdkPath(_cache), 'bin', _artifactToFileName(artifact, _platform));
      case Artifact.flutterMacOSFramework:
      case Artifact.linuxDesktopPath:
@ -925,13 +941,12 @@ class CachedLocalEngineArtifacts implements Artifacts {
      case Artifact.engineDartSdkPath:
        return _getDartSdkPath();
      case Artifact.engineDartBinary:
+      case Artifact.engineDartAotRuntime:
        return _fileSystem.path.join(_getDartSdkPath(), 'bin', artifactFileName);
      case Artifact.dart2jsSnapshot:
-        return _fileSystem.path.join(_getDartSdkPath(), 'bin', 'snapshots', artifactFileName);
+      case Artifact.dart2wasmSnapshot:
      case Artifact.frontendServerSnapshotForEngineDartSdk:
-        return _fileSystem.path.join(
-          _getDartSdkPath(), 'bin', 'snapshots', artifactFileName,
-        );
+        return _fileSystem.path.join(_getDartSdkPath(), 'bin', 'snapshots', artifactFileName);
    }
  }

@ -1048,10 +1063,12 @@ class CachedLocalWebSdkArtifacts implements Artifacts {
        case Artifact.engineDartSdkPath:
          return _getDartSdkPath();
        case Artifact.engineDartBinary:
+        case Artifact.engineDartAotRuntime:
          return _fileSystem.path.join(
            _getDartSdkPath(), 'bin',
            _artifactToFileName(artifact, _platform, mode));
        case Artifact.dart2jsSnapshot:
+        case Artifact.dart2wasmSnapshot:
        case Artifact.frontendServerSnapshotForEngineDartSdk:
          return _fileSystem.path.join(
            _getDartSdkPath(), 'bin', 'snapshots',
--- a/packages/flutter_tools/lib/src/build_info.dart
+++ b/packages/flutter_tools/lib/src/build_info.dart
@ -914,8 +914,8 @@ String getMacOSBuildDirectory() {
 }

 /// Returns the web build output directory.
-String getWebBuildDirectory() {
-  return globals.fs.path.join(getBuildDirectory(), 'web');
+String getWebBuildDirectory([bool isWasm = false]) {
+  return globals.fs.path.join(getBuildDirectory(), isWasm ? 'web_wasm' : 'web');
 }

 /// Returns the Linux build output directory.
--- a/packages/flutter_tools/lib/src/build_system/targets/web.dart
+++ b/packages/flutter_tools/lib/src/build_system/targets/web.dart
@ -22,6 +22,7 @@ import '../../web/compile.dart';
 import '../../web/file_generators/flutter_js.dart' as flutter_js;
 import '../../web/file_generators/flutter_service_worker_js.dart';
 import '../../web/file_generators/main_dart.dart' as main_dart;
+import '../../web/file_generators/wasm_bootstrap.dart' as wasm_bootstrap;
 import '../build_system.dart';
 import '../depfile.dart';
 import '../exceptions.dart';
@ -141,13 +142,11 @@ class WebEntrypointTarget extends Target {
 }

 /// Compiles a web entry point with dart2js.
-class Dart2JSTarget extends Target {
-  const Dart2JSTarget(this.webRenderer);
+abstract class Dart2WebTarget extends Target {
+  const Dart2WebTarget(this.webRenderer);

  final WebRendererMode webRenderer;
-
-  @override
-  String get name => 'dart2js';
+  Source get compilerSnapshot;

  @override
  List<Target> get dependencies => const <Target>[
@ -156,22 +155,17 @@ class Dart2JSTarget extends Target {
  ];

  @override
-  List<Source> get inputs => const <Source>[
-    Source.hostArtifact(HostArtifact.flutterWebSdk),
-    Source.artifact(Artifact.dart2jsSnapshot),
-    Source.artifact(Artifact.engineDartBinary),
-    Source.pattern('{BUILD_DIR}/main.dart'),
-    Source.pattern('{PROJECT_DIR}/.dart_tool/package_config_subset'),
+  List<Source> get inputs => <Source>[
+    const Source.hostArtifact(HostArtifact.flutterWebSdk),
+    compilerSnapshot,
+    const Source.artifact(Artifact.engineDartBinary),
+    const Source.pattern('{BUILD_DIR}/main.dart'),
+    const Source.pattern('{PROJECT_DIR}/.dart_tool/package_config_subset'),
  ];

  @override
  List<Source> get outputs => const <Source>[];

-  @override
-  List<String> get depfiles => const <String>[
-    'dart2js.d',
-  ];
-
  String _collectOutput(ProcessResult result) {
    final String stdout = result.stdout is List<int>
        ? utf8.decode(result.stdout as List<int>)
@ -181,6 +175,21 @@ class Dart2JSTarget extends Target {
        : result.stderr as String;
    return stdout + stderr;
  }
+}
+
+class Dart2JSTarget extends Dart2WebTarget {
+  Dart2JSTarget(super.webRenderer);
+
+  @override
+  String get name => 'dart2js';
+
+  @override
+  Source get compilerSnapshot => const Source.artifact(Artifact.dart2jsSnapshot);
+
+  @override
+  List<String> get depfiles => const <String>[
+    'dart2js.d',
+  ];

  @override
  Future<void> build(Environment environment) async {
@ -270,29 +279,94 @@ class Dart2JSTarget extends Target {
  }
 }

-/// Unpacks the dart2js compilation and resources to a given output directory.
+class Dart2WasmTarget extends Dart2WebTarget {
+  Dart2WasmTarget(super.webRenderer);
+
+  @override
+  Future<void> build(Environment environment) async {
+    final String? buildModeEnvironment = environment.defines[kBuildMode];
+    if (buildModeEnvironment == null) {
+      throw MissingDefineException(kBuildMode, name);
+    }
+    final BuildMode buildMode = getBuildModeForName(buildModeEnvironment);
+    final Artifacts artifacts = globals.artifacts!;
+    final File outputWasmFile = environment.buildDir.childFile('main.dart.wasm');
+    final String dartSdkPath = artifacts.getArtifactPath(Artifact.engineDartSdkPath, platform: TargetPlatform.web_javascript);
+    final String dartSdkRoot = environment.fileSystem.directory(dartSdkPath).parent.path;
+
+    final List<String> compilationArgs = <String>[
+      artifacts.getArtifactPath(Artifact.engineDartAotRuntime, platform: TargetPlatform.web_javascript),
+      '--disable-dart-dev',
+      artifacts.getArtifactPath(Artifact.dart2wasmSnapshot, platform: TargetPlatform.web_javascript),
+      if (buildMode == BuildMode.profile)
+        '-Ddart.vm.profile=true'
+      else
+        '-Ddart.vm.product=true',
+      ...decodeCommaSeparated(environment.defines, kExtraFrontEndOptions),
+      for (final String dartDefine in decodeDartDefines(environment.defines, kDartDefines))
+        '-D$dartDefine',
+      '--packages=.dart_tool/package_config.json',
+      '--dart-sdk=$dartSdkPath',
+      '--multi-root-scheme',
+      'org-dartlang-sdk',
+      '--multi-root',
+      artifacts.getHostArtifact(HostArtifact.flutterWebSdk).path,
+      '--multi-root',
+      dartSdkRoot,
+      '--libraries-spec',
+      artifacts.getHostArtifact(HostArtifact.flutterWebLibrariesJson).path,
+
+      environment.buildDir.childFile('main.dart').path, // dartfile
+      outputWasmFile.path,
+    ];
+    final ProcessResult compileResult = await globals.processManager.run(compilationArgs);
+    if (compileResult.exitCode != 0) {
+      throw Exception(_collectOutput(compileResult));
+    }
+  }
+
+  @override
+  Source get compilerSnapshot => const Source.artifact(Artifact.dart2wasmSnapshot);
+
+  @override
+  String get name => 'dart2wasm';
+
+  @override
+  List<Source> get outputs => const <Source>[
+    Source.pattern('{OUTPUT_DIR}/main.dart.wasm'),
+  ];
+
+  // TODO(jacksongardner): override `depfiles` once dart2wasm begins producing
+  // them: https://github.com/dart-lang/sdk/issues/50747
+}
+
+/// Unpacks the dart2js or dart2wasm compilation and resources to a given
+/// output directory.
 class WebReleaseBundle extends Target {
-  const WebReleaseBundle(this.webRenderer);
+  const WebReleaseBundle(this.webRenderer, this.isWasm);

  final WebRendererMode webRenderer;
+  final bool isWasm;
+
+  String get outputFileName => isWasm ? 'main.dart.wasm' : 'main.dart.js';

  @override
  String get name => 'web_release_bundle';

  @override
  List<Target> get dependencies => <Target>[
-    Dart2JSTarget(webRenderer),
+    if (isWasm) Dart2WasmTarget(webRenderer) else Dart2JSTarget(webRenderer),
  ];

  @override
-  List<Source> get inputs => const <Source>[
-    Source.pattern('{BUILD_DIR}/main.dart.js'),
-    Source.pattern('{PROJECT_DIR}/pubspec.yaml'),
+  List<Source> get inputs => <Source>[
+    Source.pattern('{BUILD_DIR}/$outputFileName'),
+    const Source.pattern('{PROJECT_DIR}/pubspec.yaml'),
  ];

  @override
-  List<Source> get outputs => const <Source>[
-    Source.pattern('{OUTPUT_DIR}/main.dart.js'),
+  List<Source> get outputs => <Source>[
+    Source.pattern('{OUTPUT_DIR}/$outputFileName'),
  ];

  @override
@ -306,7 +380,7 @@ class WebReleaseBundle extends Target {
  Future<void> build(Environment environment) async {
    for (final File outputFile in environment.buildDir.listSync(recursive: true).whereType<File>()) {
      final String basename = globals.fs.path.basename(outputFile.path);
-      if (!basename.contains('main.dart.js')) {
+      if (!basename.contains(outputFileName)) {
        continue;
      }
      // Do not copy the deps file.
@ -318,6 +392,12 @@ class WebReleaseBundle extends Target {
      );
    }

+    if (isWasm) {
+      // TODO(jacksongardner): Enable icon tree shaking once dart2wasm can do a two-phase compile.
+      // https://github.com/flutter/flutter/issues/117248
+      environment.defines[kIconTreeShakerFlag] = 'false';
+    }
+
    createVersionFile(environment, environment.defines);
    final Directory outputDirectory = environment.outputDir.childDirectory('assets');
    outputDirectory.createSync(recursive: true);
@ -413,10 +493,11 @@ class WebReleaseBundle extends Target {
 /// These assets can be cached forever and are only invalidated when the
 /// Flutter SDK is upgraded to a new version.
 class WebBuiltInAssets extends Target {
-  const WebBuiltInAssets(this.fileSystem, this.cache);
+  const WebBuiltInAssets(this.fileSystem, this.cache, this.isWasm);

  final FileSystem fileSystem;
  final Cache cache;
+  final bool isWasm;

  @override
  String get name => 'web_static_assets';
@ -451,6 +532,21 @@ class WebBuiltInAssets extends Target {
      file.copySync(targetPath);
    }

+    if (isWasm) {
+      final String dartSdkPath =
+        globals.artifacts!.getArtifactPath(Artifact.engineDartSdkPath);
+      final File dart2wasmRuntime = fileSystem.directory(dartSdkPath)
+        .childDirectory('bin')
+        .childFile('dart2wasm_runtime.mjs');
+      final String targetPath = fileSystem.path.join(
+        environment.outputDir.path,
+        'dart2wasm_runtime.mjs');
+      dart2wasmRuntime.copySync(targetPath);
+
+      final File bootstrapFile = environment.outputDir.childFile('main.dart.js');
+      bootstrapFile.writeAsStringSync(wasm_bootstrap.generateWasmBootstrapFile());
+    }
+
    // Write the flutter.js file
    final File flutterJsFile = environment.outputDir.childFile('flutter.js');
    flutterJsFile.writeAsStringSync(flutter_js.generateFlutterJsFile());
@ -459,20 +555,21 @@ class WebBuiltInAssets extends Target {

 /// Generate a service worker for a web target.
 class WebServiceWorker extends Target {
-  const WebServiceWorker(this.fileSystem, this.cache, this.webRenderer);
+  const WebServiceWorker(this.fileSystem, this.cache, this.webRenderer, this.isWasm);

  final FileSystem fileSystem;
  final Cache cache;
  final WebRendererMode webRenderer;
+  final bool isWasm;

  @override
  String get name => 'web_service_worker';

  @override
  List<Target> get dependencies => <Target>[
-    Dart2JSTarget(webRenderer),
-    WebReleaseBundle(webRenderer),
-    WebBuiltInAssets(fileSystem, cache),
+    if (isWasm) Dart2WasmTarget(webRenderer) else Dart2JSTarget(webRenderer),
+    WebReleaseBundle(webRenderer, isWasm),
+    WebBuiltInAssets(fileSystem, cache, isWasm),
  ];

  @override
--- a/packages/flutter_tools/lib/src/commands/build_web.dart
+++ b/packages/flutter_tools/lib/src/commands/build_web.dart
@ -42,6 +42,10 @@ class BuildWebCommand extends BuildSubCommand {
            'to view and debug the original source code of a compiled and minified Dart '
            'application.'
    );
+    argParser.addFlag(
+      'wasm',
+      help: 'Compile to WebAssembly rather than Javascript (experimental).'
+    );

    argParser.addOption('pwa-strategy',
      defaultsTo: kOfflineFirst,
@ -140,6 +144,7 @@ class BuildWebCommand extends BuildSubCommand {
      stringArgDeprecated('pwa-strategy')!,
      boolArgDeprecated('source-maps'),
      boolArgDeprecated('native-null-assertions'),
+      boolArgDeprecated('wasm'),
      baseHref: baseHref,
      dart2jsOptimization: stringArgDeprecated('dart2js-optimization'),
      outputDirectoryPath: outputDirectoryPath,
--- a/packages/flutter_tools/lib/src/isolated/resident_web_runner.dart
+++ b/packages/flutter_tools/lib/src/isolated/resident_web_runner.dart
@ -298,6 +298,7 @@ class ResidentWebRunner extends ResidentRunner {
            kNoneWorker,
            true,
            debuggingOptions.nativeNullAssertions,
+            false,
          );
        }
        await device!.device!.startApp(
@ -370,6 +371,7 @@ class ResidentWebRunner extends ResidentRunner {
          kNoneWorker,
          true,
          debuggingOptions.nativeNullAssertions,
+          false,
          baseHref: kBaseHref,
        );
      } on ToolExit {
--- a/packages/flutter_tools/lib/src/web/compile.dart
+++ b/packages/flutter_tools/lib/src/web/compile.dart
@ -25,7 +25,8 @@ Future<void> buildWeb(
  bool csp,
  String serviceWorkerStrategy,
  bool sourceMaps,
-  bool nativeNullAssertions, {
+  bool nativeNullAssertions,
+  bool isWasm, {
  String? dart2jsOptimization,
  String? baseHref,
  bool dumpInfo = false,
@ -35,7 +36,7 @@ Future<void> buildWeb(
  final bool hasWebPlugins = (await findPlugins(flutterProject))
    .any((Plugin p) => p.platforms.containsKey(WebPlugin.kConfigKey));
  final Directory outputDirectory = outputDirectoryPath == null
-      ? globals.fs.directory(getWebBuildDirectory())
+      ? globals.fs.directory(getWebBuildDirectory(isWasm))
      : globals.fs.directory(outputDirectoryPath);
  outputDirectory.createSync(recursive: true);

@ -51,7 +52,7 @@ Future<void> buildWeb(
  final Stopwatch sw = Stopwatch()..start();
  try {
    final BuildResult result = await globals.buildSystem.build(
-      WebServiceWorker(globals.fs, globals.cache, buildInfo.webRenderer),
+      WebServiceWorker(globals.fs, globals.cache, buildInfo.webRenderer, isWasm),
      Environment(
        projectDir: globals.fs.currentDirectory,
        outputDir: outputDirectory,
--- a/packages/flutter_tools/lib/src/web/file_generators/wasm_bootstrap.dart
+++ b/packages/flutter_tools/lib/src/web/file_generators/wasm_bootstrap.dart
@ -0,0 +1,31 @@
+// 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.
+
+String generateWasmBootstrapFile() {
+  return r'''
+// 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.
+
+(async function () {
+  let dart2wasm_runtime;
+  let moduleInstance;
+  try {
+    const dartModulePromise = WebAssembly.compileStreaming(fetch("main.dart.wasm"));
+    dart2wasm_runtime = await import('./dart2wasm_runtime.mjs');
+    moduleInstance = await dart2wasm_runtime.instantiate(dartModulePromise, {});
+  } catch (exception) {
+    console.error(`Failed to fetch and instantiate wasm module: ${exception}`);
+  }
+
+  if (moduleInstance) {
+    try {
+      await dart2wasm_runtime.invoke(moduleInstance);
+    } catch (exception) {
+      console.error(`Exception while invoking test: ${exception}`);
+    }
+  }
+})();
+''';
+}
--- a/packages/flutter_tools/test/general.shard/build_system/targets/web_test.dart
+++ b/packages/flutter_tools/test/general.shard/build_system/targets/web_test.dart
@ -100,7 +100,7 @@ void main() {
    webResources.childFile('index.html')
        .createSync(recursive: true);
    environment.buildDir.childFile('main.dart.js').createSync();
-    await const WebReleaseBundle(WebRendererMode.autoDetect).build(environment);
+    await const WebReleaseBundle(WebRendererMode.autoDetect, false).build(environment);

    expect(environment.outputDir.childFile('version.json'), exists);
  }));
@ -112,7 +112,7 @@ void main() {
      final Directory webResources = environment.projectDir.childDirectory('web');
      webResources.childFile('index.html').createSync(recursive: true);
      environment.buildDir.childFile('main.dart.js').createSync();
-      await const WebReleaseBundle(WebRendererMode.autoDetect).build(environment);
+      await const WebReleaseBundle(WebRendererMode.autoDetect, false).build(environment);

      final String versionFile = environment.outputDir
          .childFile('version.json')
@ -130,7 +130,7 @@ void main() {
 <!DOCTYPE html><html><base href="$kBaseHrefPlaceholder"><head></head></html>
    ''');
    environment.buildDir.childFile('main.dart.js').createSync();
-    await const WebReleaseBundle(WebRendererMode.autoDetect).build(environment);
+    await const WebReleaseBundle(WebRendererMode.autoDetect, false).build(environment);

    expect(environment.outputDir.childFile('index.html').readAsStringSync(), contains('/basehreftest/'));
  }));
@ -143,7 +143,7 @@ void main() {
 <!DOCTYPE html><html><head><base href='/basehreftest/'></head></html>
    ''');
    environment.buildDir.childFile('main.dart.js').createSync();
-    await const WebReleaseBundle(WebRendererMode.autoDetect).build(environment);
+    await const WebReleaseBundle(WebRendererMode.autoDetect, false).build(environment);

    expect(environment.outputDir.childFile('index.html').readAsStringSync(), contains('/basehreftest/'));
  }));
@ -165,7 +165,7 @@ void main() {
      .writeAsStringSync('A');
    environment.buildDir.childFile('main.dart.js').createSync();

-    await const WebReleaseBundle(WebRendererMode.autoDetect).build(environment);
+    await const WebReleaseBundle(WebRendererMode.autoDetect, false).build(environment);

    expect(environment.outputDir.childFile('foo.txt')
      .readAsStringSync(), 'A');
@ -177,7 +177,7 @@ void main() {
    // Update to arbitrary resource file triggers rebuild.
    webResources.childFile('foo.txt').writeAsStringSync('B');

-    await const WebReleaseBundle(WebRendererMode.autoDetect).build(environment);
+    await const WebReleaseBundle(WebRendererMode.autoDetect, false).build(environment);

    expect(environment.outputDir.childFile('foo.txt')
      .readAsStringSync(), 'B');
@ -358,7 +358,7 @@ void main() {
      ]
    ));

-    await const Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
+    await Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
  }, overrides: <Type, Generator>{
    ProcessManager: () => processManager,
  }));
@ -396,7 +396,7 @@ void main() {
      ]
    ));

-    await const Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
+    await Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
  }, overrides: <Type, Generator>{
    ProcessManager: () => processManager,
  }));
@ -430,7 +430,7 @@ void main() {
      ]
    ));

-    await const Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
+    await Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
  }, overrides: <Type, Generator>{
    ProcessManager: () => processManager,
  }));
@ -463,7 +463,7 @@ void main() {
      ]
    ));

-    await const Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
+    await Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
  }, overrides: <Type, Generator>{
    ProcessManager: () => processManager,
  }));
@ -499,7 +499,7 @@ void main() {
      ]
    ));

-    await const Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
+    await Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
  }, overrides: <Type, Generator>{
    ProcessManager: () => processManager,
  }));
@ -533,7 +533,7 @@ void main() {
      ]
    ));

-    await const Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
+    await Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
  }, overrides: <Type, Generator>{
    ProcessManager: () => processManager,
  }));
@ -556,7 +556,7 @@ void main() {
          .writeAsStringSync('file:///a.dart');
      },
    ));
-    await const Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
+    await Dart2JSTarget(WebRendererMode.autoDetect).build(environment);

    expect(environment.buildDir.childFile('dart2js.d'), exists);
    final Depfile depfile = depfileService.parse(environment.buildDir.childFile('dart2js.d'));
@ -601,7 +601,7 @@ void main() {
      ]
    ));

-    await const Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
+    await Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
  }, overrides: <Type, Generator>{
    ProcessManager: () => processManager,
  }));
@ -633,7 +633,7 @@ void main() {
      ]
    ));

-    await const Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
+    await Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
  }, overrides: <Type, Generator>{
    ProcessManager: () => processManager,
  }));
@ -673,7 +673,7 @@ void main() {
      ]
    ));

-    await const Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
+    await Dart2JSTarget(WebRendererMode.autoDetect).build(environment);
  }, overrides: <Type, Generator>{
    ProcessManager: () => processManager,
  }));
@ -709,7 +709,7 @@ void main() {
      ]
    ));

-    await const Dart2JSTarget(WebRendererMode.canvaskit).build(environment);
+    await Dart2JSTarget(WebRendererMode.canvaskit).build(environment);
  }, overrides: <Type, Generator>{
    ProcessManager: () => processManager,
  }));
@ -745,7 +745,40 @@ void main() {
      ]
    ));

-    await const Dart2JSTarget(WebRendererMode.canvaskit).build(environment);
+    await Dart2JSTarget(WebRendererMode.canvaskit).build(environment);
+  }, overrides: <Type, Generator>{
+    ProcessManager: () => processManager,
+  }));
+
+  test('Dart2WasmTarget invokes dart2wasm with dart defines', () => testbed.run(() async {
+    environment.defines[kBuildMode] = 'profile';
+    environment.defines[kDartDefines] = encodeDartDefines(<String>['FOO=bar', 'BAZ=qux']);
+
+    processManager.addCommand(FakeCommand(
+      command: <String>[
+        'bin/cache/dart-sdk/bin/dartaotruntime',
+        '--disable-dart-dev',
+        'bin/cache/dart-sdk/bin/snapshots/dart2wasm_product.snapshot',
+        '-Ddart.vm.profile=true',
+        '-DFOO=bar',
+        '-DBAZ=qux',
+        '--packages=.dart_tool/package_config.json',
+        '--dart-sdk=bin/cache/dart-sdk',
+        '--multi-root-scheme',
+        'org-dartlang-sdk',
+        '--multi-root',
+        'bin/cache/flutter_web_sdk',
+        '--multi-root',
+        'bin/cache',
+        '--libraries-spec',
+        'bin/cache/flutter_web_sdk/libraries.json',
+
+        environment.buildDir.childFile('main.dart').absolute.path,
+        environment.buildDir.childFile('main.dart.wasm').absolute.path,
+      ])
+    );
+
+    await Dart2WasmTarget(WebRendererMode.canvaskit).build(environment);
  }, overrides: <Type, Generator>{
    ProcessManager: () => processManager,
  }));
@ -772,7 +805,7 @@ void main() {
    environment.outputDir.childDirectory('a').childFile('a.txt')
      ..createSync(recursive: true)
      ..writeAsStringSync('A');
-    await WebServiceWorker(globals.fs, globals.cache, WebRendererMode.autoDetect).build(environment);
+    await WebServiceWorker(globals.fs, globals.cache, WebRendererMode.autoDetect, false).build(environment);

    expect(environment.outputDir.childFile('flutter_service_worker.js'), exists);
    // Contains file hash.
@ -791,7 +824,7 @@ void main() {
    environment.outputDir
      .childFile('index.html')
      .createSync(recursive: true);
-    await WebServiceWorker(globals.fs, globals.cache, WebRendererMode.autoDetect).build(environment);
+    await WebServiceWorker(globals.fs, globals.cache, WebRendererMode.autoDetect, false).build(environment);

    expect(environment.outputDir.childFile('flutter_service_worker.js'), exists);
    // Contains file hash for both `/` and index.html.
@ -809,7 +842,7 @@ void main() {
    environment.outputDir
      .childFile('main.dart.js.map')
      .createSync(recursive: true);
-    await WebServiceWorker(globals.fs, globals.cache, WebRendererMode.autoDetect).build(environment);
+    await WebServiceWorker(globals.fs, globals.cache, WebRendererMode.autoDetect, false).build(environment);

    // No caching of source maps.
    expect(environment.outputDir.childFile('flutter_service_worker.js').readAsStringSync(),
@ -824,10 +857,25 @@ void main() {
      ..createSync(recursive: true)
      ..writeAsStringSync('OL');

-    await WebBuiltInAssets(globals.fs, globals.cache).build(environment);
+    await WebBuiltInAssets(globals.fs, globals.cache, false).build(environment);

    // No caching of source maps.
    expect(environment.outputDir.childFile('flutter.js').readAsStringSync(),
      equals(flutter_js.generateFlutterJsFile()));
  }));
+
+  test('wasm build copies and generates specific files', () => testbed.run(() async {
+    globals.fs.file('bin/cache/dart-sdk/bin/dart2wasm_runtime.mjs')
+      .createSync(recursive: true);
+    globals.fs.file('bin/cache/flutter_web_sdk/canvaskit/canvaskit.wasm')
+      .createSync(recursive: true);
+
+    await WebBuiltInAssets(globals.fs, globals.cache, true).build(environment);
+
+    expect(environment.outputDir.childFile('dart2wasm_runtime.mjs').existsSync(), true);
+    expect(environment.outputDir.childFile('main.dart.js').existsSync(), true);
+    expect(environment.outputDir.childDirectory('canvaskit')
+      .childFile('canvaskit.wasm')
+      .existsSync(), true);
+  }));
 }
--- a/packages/flutter_tools/test/integration.shard/flutter_build_wasm_test.dart
+++ b/packages/flutter_tools/test/integration.shard/flutter_build_wasm_test.dart
@ -0,0 +1,60 @@
+// 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.
+
+import 'dart:io';
+
+import 'package:file_testing/file_testing.dart';
+import 'package:flutter_tools/src/base/file_system.dart';
+
+import '../src/common.dart';
+import 'test_utils.dart';
+
+void main() {
+  late Directory tempDir;
+  late String flutterBin;
+  late Directory exampleAppDir;
+
+  setUp(() async {
+    tempDir = createResolvedTempDirectorySync('flutter_web_wasm_test.');
+    flutterBin = fileSystem.path.join(
+      getFlutterRoot(),
+      'bin',
+      'flutter',
+    );
+    exampleAppDir = tempDir.childDirectory('test_app');
+
+    processManager.runSync(<String>[
+      flutterBin,
+      'create',
+      '--platforms=web',
+      'test_app',
+    ], workingDirectory: tempDir.path);
+  });
+
+  test('building web with --wasm produces expected files', () async {
+    final ProcessResult result = processManager.runSync(<String>[
+      flutterBin,
+      'build',
+      'web',
+      '--wasm',
+    ], workingDirectory: exampleAppDir.path);
+    expect(result.exitCode, 0);
+
+    final Directory appBuildDir = fileSystem.directory(fileSystem.path.join(
+      exampleAppDir.path,
+      'build',
+      'web_wasm'
+    ));
+    for (final String filename in const <String>[
+      'dart2wasm_runtime.mjs',
+      'flutter.js',
+      'flutter_service_worker.js',
+      'index.html',
+      'main.dart.wasm',
+      'main.dart.js',
+    ]) {
+      expect(appBuildDir.childFile(filename), exists);
+    }
+  });
+}