Adding support for using the Frontend Server with the Legacy/DDC modu…

dwds/CHANGELOG.md

@@ -1,5 +1,6 @@
 ## 23.0.0-wip
 - Restructure `LoadStrategy` to provide build settings. - [#2270](https://github.com/dart-lang/webdev/pull/2270)
+- Add `FrontendServerLegacyStrategyProvider` and update bootstrap generation logic for `LegacyStrategy` - [#2285](https://github.com/dart-lang/webdev/pull/2285)
 
 ## 22.1.0
 - Update `package:vm_service` constraint to `^13.0.0`. - [#2265](https://github.com/dart-lang/webdev/pull/2265)

dwds/lib/dwds.dart

@@ -19,6 +19,8 @@ export 'src/handlers/dev_handler.dart' show AppConnectionException;
 export 'src/handlers/socket_connections.dart';
 export 'src/loaders/build_runner_require.dart'
     show BuildRunnerRequireStrategyProvider;
+export 'src/loaders/frontend_server_legacy.dart'
+    show FrontendServerLegacyStrategyProvider;
 export 'src/loaders/frontend_server_require.dart'
     show FrontendServerRequireStrategyProvider;
 export 'src/loaders/legacy.dart' show LegacyStrategy;
@@ -32,7 +34,11 @@ export 'src/readers/proxy_server_asset_reader.dart' show ProxyServerAssetReader;
 export 'src/servers/devtools.dart';
 export 'src/services/chrome_debug_exception.dart' show ChromeDebugException;
 export 'src/services/expression_compiler.dart'
-    show ExpressionCompilationResult, ExpressionCompiler, ModuleInfo;
+    show
+        ExpressionCompilationResult,
+        ExpressionCompiler,
+        ModuleInfo,
+        CompilerOptions;
 export 'src/services/expression_compiler_service.dart'
     show ExpressionCompilerService;
 export 'src/utilities/sdk_configuration.dart'

dwds/lib/src/loaders/frontend_server_legacy.dart

@@ -0,0 +1,116 @@
+// Copyright 2023 The Dart 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 'package:dwds/src/debugging/metadata/provider.dart';
+import 'package:dwds/src/loaders/legacy.dart';
+import 'package:dwds/src/loaders/strategy.dart';
+import 'package:dwds/src/readers/asset_reader.dart';
+import 'package:dwds/src/services/expression_compiler.dart';
+import 'package:path/path.dart' as p;
+
+/// Provides a [LegacyStrategy] suitable for use with Frontend Server.
+class FrontendServerLegacyStrategyProvider {
+  final ReloadConfiguration _configuration;
+  final AssetReader _assetReader;
+  final PackageUriMapper _packageUriMapper;
+  final Future<Map<String, String>> Function() _digestsProvider;
+  final String _basePath;
+  final BuildSettings _buildSettings;
+
+  late final LegacyStrategy _legacyStrategy = LegacyStrategy(
+    _configuration,
+    _moduleProvider,
+    (_) => _digestsProvider(),
+    _moduleForServerPath,
+    _serverPathForModule,
+    _sourceMapPathForModule,
+    _serverPathForAppUri,
+    _moduleInfoForProvider,
+    _assetReader,
+    _buildSettings,
+    (String _) => null,
+    null,
+  );
+
+  FrontendServerLegacyStrategyProvider(
+    this._configuration,
+    this._assetReader,
+    this._packageUriMapper,
+    this._digestsProvider,
+    this._buildSettings,
+  ) : _basePath = _assetReader.basePath;
+
+  LegacyStrategy get strategy => _legacyStrategy;
+
+  String _removeBasePath(String path) {
+    if (_basePath.isEmpty) return path;
+
+    final stripped = stripLeadingSlashes(path);
+    return stripLeadingSlashes(stripped.substring(_basePath.length));
+  }
+
+  String _addBasePath(String serverPath) => _basePath.isEmpty
+      ? stripLeadingSlashes(serverPath)
+      : '$_basePath/${stripLeadingSlashes(serverPath)}';
+
+  Future<Map<String, String>> _moduleProvider(
+    MetadataProvider metadataProvider,
+  ) async =>
+      (await metadataProvider.moduleToModulePath).map(
+        (key, value) =>
+            MapEntry(key, stripLeadingSlashes(removeJsExtension(value))),
+      );
+
+  Future<String?> _moduleForServerPath(
+    MetadataProvider metadataProvider,
+    String serverPath,
+  ) async {
+    final modulePathToModule = await metadataProvider.modulePathToModule;
+    final relativeServerPath = _removeBasePath(serverPath);
+    return modulePathToModule[relativeServerPath];
+  }
+
+  Future<String> _serverPathForModule(
+    MetadataProvider metadataProvider,
+    String module,
+  ) async =>
+      _addBasePath((await metadataProvider.moduleToModulePath)[module] ?? '');
+
+  Future<String> _sourceMapPathForModule(
+    MetadataProvider metadataProvider,
+    String module,
+  ) async =>
+      _addBasePath((await metadataProvider.moduleToSourceMap)[module] ?? '');
+
+  String? _serverPathForAppUri(String appUrl) {
+    final appUri = Uri.parse(appUrl);
+    if (appUri.isScheme('org-dartlang-app')) {
+      return _addBasePath(appUri.path);
+    }
+    if (appUri.isScheme('package')) {
+      final resolved = _packageUriMapper.packageUriToServerPath(appUri);
+      if (resolved != null) {
+        return resolved;
+      }
+    }
+    return null;
+  }
+
+  Future<Map<String, ModuleInfo>> _moduleInfoForProvider(
+    MetadataProvider metadataProvider,
+  ) async {
+    final modules = await metadataProvider.moduleToModulePath;
+    final result = <String, ModuleInfo>{};
+    for (var module in modules.keys) {
+      final modulePath = modules[module]!;
+      result[module] = ModuleInfo(
+        // TODO: Save locations of full kernel files in ddc metadata.
+        // Issue: https://github.com/dart-lang/sdk/issues/43684
+        p.setExtension(modulePath, '.full.dill'),
+        p.setExtension(modulePath, '.dill'),
+      );
+    }
+    return result;
+  }
+}

dwds/lib/src/loaders/legacy.dart

@@ -2,17 +2,72 @@
 // 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:convert';
+
 import 'package:dwds/src/debugging/metadata/provider.dart';
 import 'package:dwds/src/loaders/strategy.dart';
 import 'package:dwds/src/readers/asset_reader.dart';
 import 'package:dwds/src/services/expression_compiler.dart';
+import 'package:path/path.dart' as p;
 import 'package:shelf/shelf.dart';
 
+String removeJsExtension(String path) =>
+    path.endsWith('.js') ? p.withoutExtension(path) : path;
+
+String addJsExtension(String path) => '$path.js';
+
+/// JavaScript snippet to determine the base URL of the current path.
+const _baseUrlScript = '''
+var baseUrl = (function () {
+  // Attempt to detect --precompiled mode for tests, and set the base url
+  // appropriately, otherwise set it to '/'.
+  var pathParts = location.pathname.split("/");
+  if (pathParts[0] == "") {
+    pathParts.shift();
+  }
+  if (pathParts.length > 1 && pathParts[1] == "test") {
+    return "/" + pathParts.slice(0, 2).join("/") + "/";
+  }
+  // Attempt to detect base url using <base href> html tag
+  // base href should start and end with "/"
+  if (typeof document !== 'undefined') {
+    var el = document.getElementsByTagName('base');
+    if (el && el[0] && el[0].getAttribute("href") && el[0].getAttribute
+    ("href").startsWith("/") && el[0].getAttribute("href").endsWith("/")){
+      return el[0].getAttribute("href");
+    }
+  }
+  // return default value
+  return "/";
+}());
+''';
+
 /// A load strategy for the legacy module system.
 class LegacyStrategy extends LoadStrategy {
   @override
   final ReloadConfiguration reloadConfiguration;
 
+  /// Returns a map of module name to corresponding server path (excluding .js)
+  /// for the provided Dart application entrypoint.
+  ///
+  /// For example:
+  ///
+  ///   web/main -> main.ddc
+  ///   packages/path/path -> packages/path/path.ddc
+  ///
+  final Future<Map<String, String>> Function(MetadataProvider metadataProvider)
+      _moduleProvider;
+
+  /// Returns a map of module name to corresponding digest value.
+  ///
+  /// For example:
+  ///
+  ///   web/main -> 8363b363f74b41cac955024ab8b94a3f
+  ///   packages/path/path -> d348c2a4647e998011fe305f74f22961
+  ///
+  final Future<Map<String, String>> Function(MetadataProvider metadataProvider)
+      _digestsProvider;
+
   /// Returns the module for the corresponding server path.
   ///
   /// For example:
@@ -75,6 +130,8 @@ class LegacyStrategy extends LoadStrategy {
 
   LegacyStrategy(
     this.reloadConfiguration,
+    this._moduleProvider,
+    this._digestsProvider,
     this._moduleForServerPath,
     this._serverPathForModule,
     this._sourceMapPathForModule,
@@ -87,7 +144,11 @@ class LegacyStrategy extends LoadStrategy {
   ) : super(assetReader, packageConfigPath: packageConfigPath);
 
   @override
-  Handler get handler => (request) => Response.notFound(request.url.toString());
+  Handler get handler => (request) async {
+        // TODO(markzipan): Implement a hot restarter that uses digests for
+        // the DDC module system.
+        return Response.notFound(request.url.toString());
+      };
 
   @override
   String get id => 'legacy';
@@ -102,12 +163,27 @@ class LegacyStrategy extends LoadStrategy {
   String get loadModuleSnippet => 'dart_library.import';
 
   @override
-  Future<String> bootstrapFor(String entrypoint) async => '';
+  Future<String> bootstrapFor(String entrypoint) async =>
+      await _legacyLoaderSetup(entrypoint);
 
   @override
   String loadClientSnippet(String clientScript) =>
       'window.\$dartLoader.forceLoadModule("$clientScript");\n';
 
+  Future<String> _legacyLoaderSetup(String entrypoint) async {
+    final metadataProvider = metadataProviderFor(entrypoint);
+    final modulePaths = await _moduleProvider(metadataProvider);
+    final scripts = <Map<String, String?>>[];
+    modulePaths.forEach((name, path) {
+      scripts.add(<String, String>{'src': '$path.js', 'id': name});
+    });
+    return '''
+$_baseUrlScript
+var scripts = ${const JsonEncoder.withIndent(" ").convert(scripts)};
+window.\$dartLoader.loadScripts(scripts);
+''';
+  }
+
   @override
   Future<String?> moduleForServerPath(String entrypoint, String serverPath) =>
       _moduleForServerPath(metadataProviderFor(entrypoint), serverPath);