Inject the gstatic CanvasKit CDN URL by default in `flutter build web` (#122772)

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

@@ -60,6 +60,7 @@ class BuildWebCommand extends BuildSubCommand {
       },
     );
     usesWebRendererOption();
+    usesWebResourcesCdnFlag();
 
     //
     // JavaScript compilation options

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

@@ -38,6 +38,7 @@ abstract class RunCommandBase extends FlutterCommand with DeviceBasedDevelopment
     usesDartDefineOption();
     usesFlavorOption();
     usesWebRendererOption();
+    usesWebResourcesCdnFlag();
     addNativeNullAssertions(hide: !verboseHelp);
     addBundleSkSLPathOption(hide: !verboseHelp);
     usesApplicationBinaryOption();

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

@@ -125,6 +125,7 @@ class FlutterOptions {
   static const String kUseApplicationBinary = 'use-application-binary';
   static const String kWebBrowserFlag = 'web-browser-flag';
   static const String kWebRendererFlag = 'web-renderer';
+  static const String kWebResourcesCdnFlag = 'web-resources-cdn';
 }
 
 /// flutter command categories for usage.
@@ -668,6 +669,14 @@ abstract class FlutterCommand extends Command<void> {
     );
   }
 
+  void usesWebResourcesCdnFlag() {
+    // TODO(hterkelsen): Default to true once we have a smoke test.
+    argParser.addFlag(
+      FlutterOptions.kWebResourcesCdnFlag,
+      help: 'Use Web static resources hosted on a CDN.',
+    );
+  }
+
   void usesDeviceUserOption() {
     argParser.addOption(FlutterOptions.kDeviceUser,
       help: 'Identifier number for a user or work profile on Android only. Run "adb shell pm list users" for available identifiers.',
@@ -1207,6 +1216,15 @@ abstract class FlutterCommand extends Command<void> {
       dartDefines = updateDartDefines(dartDefines, webRenderer);
     }
 
+    if (argParser.options.containsKey(FlutterOptions.kWebResourcesCdnFlag)) {
+      final bool hasLocalWebSdk = argParser.options.containsKey('local-web-sdk') && stringArg('local-web-sdk') != null;
+      if (boolArg(FlutterOptions.kWebResourcesCdnFlag) && !hasLocalWebSdk) {
+        if (!dartDefines.any((String define) => define.startsWith('FLUTTER_WEB_CANVASKIT_URL='))) {
+          dartDefines.add('FLUTTER_WEB_CANVASKIT_URL=https://www.gstatic.com/flutter-canvaskit/${globals.flutterVersion.engineRevision}/');
+        }
+      }
+    }
+
     return BuildInfo(buildMode,
       argParser.options.containsKey('flavor')
         ? stringArg('flavor')

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

@@ -112,7 +112,7 @@ void main() {
     );
     final CommandRunner<void> runner = createTestCommandRunner(buildCommand);
     setupFileSystemForEndToEndTest(fileSystem);
-    await runner.run(<String>['build', 'web', '--no-pub', '--dart-define=foo=a', '--dart2js-optimization=O3']);
+    await runner.run(<String>['build', 'web', '--no-pub', '--no-web-resources-cdn', '--dart-define=foo=a', '--dart2js-optimization=O3']);
 
     final Directory buildDir = fileSystem.directory(fileSystem.path.join('build', 'web'));
 
@@ -164,6 +164,7 @@ void main() {
       'build',
       'web',
       '--no-pub',
+      '--no-web-resources-cdn',
       '--output=$newBuildDir'
     ]);
 
@@ -251,6 +252,38 @@ void main() {
     ProcessManager: () => FakeProcessManager.any(),
     BuildSystem: () => TestBuildSystem.all(BuildResult(success: true)),
   });
+
+  testUsingContext('Defaults to gstatic CanvasKit artifacts', () async {
+    final TestWebBuildCommand buildCommand = TestWebBuildCommand(fileSystem: fileSystem);
+    final CommandRunner<void> runner = createTestCommandRunner(buildCommand);
+    setupFileSystemForEndToEndTest(fileSystem);
+    await runner.run(<String>['build', 'web', '--no-pub', '--web-resources-cdn']);
+    final BuildInfo buildInfo =
+        await buildCommand.webCommand.getBuildInfo(forcedBuildMode: BuildMode.debug);
+    expect(buildInfo.dartDefines, contains(startsWith('FLUTTER_WEB_CANVASKIT_URL=https://www.gstatic.com/flutter-canvaskit/')));
+  }, overrides: <Type, Generator>{
+    Platform: () => fakePlatform,
+    FileSystem: () => fileSystem,
+    FeatureFlags: () => TestFeatureFlags(isWebEnabled: true),
+    ProcessManager: () => FakeProcessManager.any(),
+    BuildSystem: () => TestBuildSystem.all(BuildResult(success: true)),
+  });
+
+  testUsingContext('Does not override custom CanvasKit URL', () async {
+    final TestWebBuildCommand buildCommand = TestWebBuildCommand(fileSystem: fileSystem);
+    final CommandRunner<void> runner = createTestCommandRunner(buildCommand);
+    setupFileSystemForEndToEndTest(fileSystem);
+    await runner.run(<String>['build', 'web', '--no-pub', '--web-resources-cdn', '--dart-define=FLUTTER_WEB_CANVASKIT_URL=abcdefg']);
+    final BuildInfo buildInfo =
+        await buildCommand.webCommand.getBuildInfo(forcedBuildMode: BuildMode.debug);
+    expect(buildInfo.dartDefines, contains('FLUTTER_WEB_CANVASKIT_URL=abcdefg'));
+  }, overrides: <Type, Generator>{
+    Platform: () => fakePlatform,
+    FileSystem: () => fileSystem,
+    FeatureFlags: () => TestFeatureFlags(isWebEnabled: true),
+    ProcessManager: () => FakeProcessManager.any(),
+    BuildSystem: () => TestBuildSystem.all(BuildResult(success: true)),
+  });
 }
 
 void setupFileSystemForEndToEndTest(FileSystem fileSystem) {