[flutter_tools] reload dart_sdk when sources update (#51067)

packages/flutter_tools/lib/src/build_runner/devfs_web.dart

@@ -45,6 +45,9 @@ class WebAssetServer implements AssetReader {
 
   /// Start the web asset server on a [hostname] and [port].
   ///
+  /// If [testMode] is true, do not actually initialize dwds or the shelf static
+  /// server.
+  ///
   /// Unhandled exceptions will throw a [ToolExit] with the error and stack
   /// trace.
   static Future<WebAssetServer> start(
@@ -53,14 +56,18 @@ class WebAssetServer implements AssetReader {
     UrlTunneller urlTunneller,
     BuildMode buildMode,
     bool enableDwds,
-    Uri entrypoint,
-  ) async {
+    Uri entrypoint, {
+    bool testMode = false,
+  }) async {
     try {
       final InternetAddress address = (await InternetAddress.lookup(hostname)).first;
       final HttpServer httpServer = await HttpServer.bind(address, port);
       final Packages packages = await loadPackagesFile(
         Uri.base.resolve('.packages'), loader: (Uri uri) => globals.fs.file(uri).readAsBytes());
       final WebAssetServer server = WebAssetServer(httpServer, packages, address);
+      if (testMode) {
+        return server;
+      }
 
       // In release builds deploy a simpler proxy server.
       if (buildMode != BuildMode.debug) {
@@ -244,8 +251,31 @@ class WebAssetServer implements AssetReader {
     return modules;
   }
 
+  @visibleForTesting
+  final File dartSdk = globals.fs.file(globals.fs.path.join(
+    globals.artifacts.getArtifactPath(Artifact.flutterWebSdk),
+    'kernel',
+    'amd',
+    'dart_sdk.js',
+  ));
+
+  @visibleForTesting
+  final File dartSdkSourcemap = globals.fs.file(globals.fs.path.join(
+    globals.artifacts.getArtifactPath(Artifact.flutterWebSdk),
+    'kernel',
+    'amd',
+    'dart_sdk.js.map',
+  ));
+
   // Attempt to resolve `path` to a dart file.
   File _resolveDartFile(String path) {
+    // Return the actual file objects so that local engine changes are automatically picked up.
+    switch (path) {
+      case '/dart_sdk.js':
+        return dartSdk;
+      case '.dart_sdk.js.map':
+        return dartSdkSourcemap;
+    }
     // If this is a dart file, it must be on the local file system and is
     // likely coming from a source map request. The tool doesn't currently
     // consider the case of Dart files as assets.
@@ -309,7 +339,12 @@ class ConnectionResult {
   final DebugConnection debugConnection;
 }
 
+/// The web specific DevFS implementation.
 class WebDevFS implements DevFS {
+  /// Create a new [WebDevFS] instance.
+  ///
+  /// [testMode] is true, do not actually initialize dwds or the shelf static
+  /// server.
   WebDevFS({
     @required this.hostname,
     @required this.port,
@@ -318,6 +353,7 @@ class WebDevFS implements DevFS {
     @required this.buildMode,
     @required this.enableDwds,
     @required this.entrypoint,
+    this.testMode = false,
   });
 
   final Uri entrypoint;
@@ -327,6 +363,7 @@ class WebDevFS implements DevFS {
   final UrlTunneller urlTunneller;
   final BuildMode buildMode;
   final bool enableDwds;
+  final bool testMode;
 
   @visibleForTesting
   WebAssetServer webAssetServer;
@@ -387,6 +424,7 @@ class WebDevFS implements DevFS {
       buildMode,
       enableDwds,
       entrypoint,
+      testMode: testMode,
     );
     return Uri.parse('http://$hostname:$port');
   }
@@ -450,8 +488,7 @@ class WebDevFS implements DevFS {
       );
       // TODO(jonahwilliams): switch to DWDS provided APIs when they are ready.
       webAssetServer.writeFile('/basic.digests', '{}');
-      webAssetServer.writeFile('/dart_sdk.js', dartSdk.readAsStringSync());
-      webAssetServer.writeFile('/dart_sdk.js.map', dartSdkSourcemap.readAsStringSync());
+
       // TODO(jonahwilliams): refactor the asset code in this and the regular devfs to
       // be shared.
       if (bundle != null) {
@@ -498,6 +535,7 @@ class WebDevFS implements DevFS {
     } on FileSystemException catch (err) {
       throwToolExit('Failed to load recompiled sources:\n$err');
     }
+
     return UpdateFSReport(
       success: true,
       syncedBytes: codeFile.lengthSync(),
@@ -515,22 +553,6 @@ class WebDevFS implements DevFS {
     'require.js',
   ));
 
-  @visibleForTesting
-  final File dartSdk = globals.fs.file(globals.fs.path.join(
-    globals.artifacts.getArtifactPath(Artifact.flutterWebSdk),
-    'kernel',
-    'amd',
-    'dart_sdk.js',
-  ));
-
-  @visibleForTesting
-  final File dartSdkSourcemap = globals.fs.file(globals.fs.path.join(
-    globals.artifacts.getArtifactPath(Artifact.flutterWebSdk),
-    'kernel',
-    'amd',
-    'dart_sdk.js.map',
-  ));
-
   @visibleForTesting
   final File stackTraceMapper = globals.fs.file(globals.fs.path.join(
     globals.artifacts.getArtifactPath(Artifact.engineDartSdkPath),

packages/flutter_tools/test/general.shard/web/devfs_web_test.dart

@@ -18,7 +18,6 @@ import 'package:flutter_tools/src/globals.dart' as globals;
 import 'package:shelf/shelf.dart';
 
 import '../../src/common.dart';
-import '../../src/io.dart';
 import '../../src/testbed.dart';
 
 const List<int> kTransparentImage = <int>[
@@ -278,7 +277,6 @@ void main() {
   }));
 
   test('Can start web server with specified assets', () => testbed.run(() async {
-    await IOOverrides.runWithIOOverrides(() async {
     final File outputFile = globals.fs.file(globals.fs.path.join('lib', 'main.dart'))
       ..createSync(recursive: true);
     outputFile.parent.childFile('a.sources').writeAsStringSync('');
@@ -304,13 +302,17 @@ void main() {
       buildMode: BuildMode.debug,
       enableDwds: false,
       entrypoint: Uri.base,
+      testMode: true,
     );
     webDevFS.requireJS.createSync(recursive: true);
-      webDevFS.dartSdk.createSync(recursive: true);
-      webDevFS.dartSdkSourcemap.createSync(recursive: true);
     webDevFS.stackTraceMapper.createSync(recursive: true);
 
     await webDevFS.create();
+    webDevFS.webAssetServer.dartSdk
+      ..createSync(recursive: true)
+      ..writeAsStringSync('HELLO');
+    webDevFS.webAssetServer.dartSdkSourcemap.createSync(recursive: true);
+
     await webDevFS.update(
       mainPath: globals.fs.path.join('lib', 'main.dart'),
       generator: residentCompiler,
@@ -322,11 +324,16 @@ void main() {
     expect(webDevFS.webAssetServer.getFile('/main.dart'), isNotNull);
     expect(webDevFS.webAssetServer.getFile('/manifest.json'), isNotNull);
     expect(webDevFS.webAssetServer.getFile('/flutter_service_worker.js'), isNotNull);
+    expect(await webDevFS.webAssetServer.dartSourceContents('/dart_sdk.js'), 'HELLO');
+
+    // Update to the SDK.
+    webDevFS.webAssetServer.dartSdk.writeAsStringSync('BELLOW');
+
+    // New SDK should be visible..
+    expect(await webDevFS.webAssetServer.dartSourceContents('/dart_sdk.js'), 'BELLOW');
 
     await webDevFS.destroy();
-      await webDevFS.dwds.stop();
-    }, FlutterIOOverrides(fileSystem: globals.fs));
-  }), skip: true); // Not clear the best way to test this, since shelf hits the real filesystem.
+  }));
 }
 
 class MockHttpServer extends Mock implements HttpServer {}