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Adding support for using the Frontend Server with the Legacy/DDC module system. (#2285)
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‎dwds/CHANGELOG.md

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

‎dwds/lib/dwds.dart

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

‎dwds/lib/src/loaders/frontend_server_legacy.dart

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@@ -0,0 +1,116 @@
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// Copyright 2023 The Dart Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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import 'package:dwds/src/debugging/metadata/provider.dart';
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import 'package:dwds/src/loaders/legacy.dart';
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import 'package:dwds/src/loaders/strategy.dart';
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import 'package:dwds/src/readers/asset_reader.dart';
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import 'package:dwds/src/services/expression_compiler.dart';
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import 'package:path/path.dart' as p;
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/// Provides a [LegacyStrategy] suitable for use with Frontend Server.
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class FrontendServerLegacyStrategyProvider {
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final ReloadConfiguration _configuration;
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final AssetReader _assetReader;
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final PackageUriMapper _packageUriMapper;
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final Future<Map<String, String>> Function() _digestsProvider;
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final String _basePath;
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final BuildSettings _buildSettings;
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late final LegacyStrategy _legacyStrategy = LegacyStrategy(
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_configuration,
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_moduleProvider,
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(_) => _digestsProvider(),
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_moduleForServerPath,
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_serverPathForModule,
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_sourceMapPathForModule,
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_serverPathForAppUri,
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_moduleInfoForProvider,
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_assetReader,
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_buildSettings,
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(String _) => null,
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null,
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);
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FrontendServerLegacyStrategyProvider(
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this._configuration,
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this._assetReader,
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this._packageUriMapper,
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this._digestsProvider,
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this._buildSettings,
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) : _basePath = _assetReader.basePath;
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LegacyStrategy get strategy => _legacyStrategy;
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String _removeBasePath(String path) {
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if (_basePath.isEmpty) return path;
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final stripped = stripLeadingSlashes(path);
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return stripLeadingSlashes(stripped.substring(_basePath.length));
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}
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String _addBasePath(String serverPath) => _basePath.isEmpty
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? stripLeadingSlashes(serverPath)
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: '$_basePath/${stripLeadingSlashes(serverPath)}';
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Future<Map<String, String>> _moduleProvider(
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MetadataProvider metadataProvider,
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) async =>
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(await metadataProvider.moduleToModulePath).map(
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(key, value) =>
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MapEntry(key, stripLeadingSlashes(removeJsExtension(value))),
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);
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Future<String?> _moduleForServerPath(
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MetadataProvider metadataProvider,
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String serverPath,
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) async {
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final modulePathToModule = await metadataProvider.modulePathToModule;
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final relativeServerPath = _removeBasePath(serverPath);
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return modulePathToModule[relativeServerPath];
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}
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Future<String> _serverPathForModule(
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MetadataProvider metadataProvider,
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String module,
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) async =>
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_addBasePath((await metadataProvider.moduleToModulePath)[module] ?? '');
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Future<String> _sourceMapPathForModule(
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MetadataProvider metadataProvider,
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String module,
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) async =>
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_addBasePath((await metadataProvider.moduleToSourceMap)[module] ?? '');
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String? _serverPathForAppUri(String appUrl) {
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final appUri = Uri.parse(appUrl);
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if (appUri.isScheme('org-dartlang-app')) {
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return _addBasePath(appUri.path);
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}
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if (appUri.isScheme('package')) {
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final resolved = _packageUriMapper.packageUriToServerPath(appUri);
93+
if (resolved != null) {
94+
return resolved;
95+
}
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}
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return null;
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}
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Future<Map<String, ModuleInfo>> _moduleInfoForProvider(
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MetadataProvider metadataProvider,
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) async {
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final modules = await metadataProvider.moduleToModulePath;
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final result = <String, ModuleInfo>{};
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for (var module in modules.keys) {
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final modulePath = modules[module]!;
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result[module] = ModuleInfo(
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// TODO: Save locations of full kernel files in ddc metadata.
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// Issue: https://github.com/dart-lang/sdk/issues/43684
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p.setExtension(modulePath, '.full.dill'),
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p.setExtension(modulePath, '.dill'),
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);
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}
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return result;
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}
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}

‎dwds/lib/src/loaders/legacy.dart

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@@ -2,17 +2,72 @@
22
// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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import 'dart:convert';
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import 'package:dwds/src/debugging/metadata/provider.dart';
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import 'package:dwds/src/loaders/strategy.dart';
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import 'package:dwds/src/readers/asset_reader.dart';
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import 'package:dwds/src/services/expression_compiler.dart';
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import 'package:path/path.dart' as p;
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import 'package:shelf/shelf.dart';
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String removeJsExtension(String path) =>
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path.endsWith('.js') ? p.withoutExtension(path) : path;
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String addJsExtension(String path) => '$path.js';
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/// JavaScript snippet to determine the base URL of the current path.
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const _baseUrlScript = '''
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var baseUrl = (function () {
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// Attempt to detect --precompiled mode for tests, and set the base url
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// appropriately, otherwise set it to '/'.
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var pathParts = location.pathname.split("/");
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if (pathParts[0] == "") {
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pathParts.shift();
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}
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if (pathParts.length > 1 && pathParts[1] == "test") {
29+
return "/" + pathParts.slice(0, 2).join("/") + "/";
30+
}
31+
// Attempt to detect base url using <base href> html tag
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// base href should start and end with "/"
33+
if (typeof document !== 'undefined') {
34+
var el = document.getElementsByTagName('base');
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if (el && el[0] && el[0].getAttribute("href") && el[0].getAttribute
36+
("href").startsWith("/") && el[0].getAttribute("href").endsWith("/")){
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return el[0].getAttribute("href");
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}
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}
40+
// return default value
41+
return "/";
42+
}());
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''';
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1145
/// A load strategy for the legacy module system.
1246
class LegacyStrategy extends LoadStrategy {
1347
@override
1448
final ReloadConfiguration reloadConfiguration;
1549

50+
/// Returns a map of module name to corresponding server path (excluding .js)
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/// for the provided Dart application entrypoint.
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///
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/// For example:
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///
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/// web/main -> main.ddc
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/// packages/path/path -> packages/path/path.ddc
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///
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final Future<Map<String, String>> Function(MetadataProvider metadataProvider)
59+
_moduleProvider;
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/// Returns a map of module name to corresponding digest value.
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///
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/// For example:
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///
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/// web/main -> 8363b363f74b41cac955024ab8b94a3f
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/// packages/path/path -> d348c2a4647e998011fe305f74f22961
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///
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final Future<Map<String, String>> Function(MetadataProvider metadataProvider)
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_digestsProvider;
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/// Returns the module for the corresponding server path.
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///
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/// For example:
@@ -75,6 +130,8 @@ class LegacyStrategy extends LoadStrategy {
75130

76131
LegacyStrategy(
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this.reloadConfiguration,
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this._moduleProvider,
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this._digestsProvider,
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this._moduleForServerPath,
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this._serverPathForModule,
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this._sourceMapPathForModule,
@@ -87,7 +144,11 @@ class LegacyStrategy extends LoadStrategy {
87144
) : super(assetReader, packageConfigPath: packageConfigPath);
88145

89146
@override
90-
Handler get handler => (request) => Response.notFound(request.url.toString());
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Handler get handler => (request) async {
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// TODO(markzipan): Implement a hot restarter that uses digests for
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// the DDC module system.
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return Response.notFound(request.url.toString());
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};
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92153
@override
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String get id => 'legacy';
@@ -102,12 +163,27 @@ class LegacyStrategy extends LoadStrategy {
102163
String get loadModuleSnippet => 'dart_library.import';
103164

104165
@override
105-
Future<String> bootstrapFor(String entrypoint) async => '';
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Future<String> bootstrapFor(String entrypoint) async =>
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await _legacyLoaderSetup(entrypoint);
106168

107169
@override
108170
String loadClientSnippet(String clientScript) =>
109171
'window.\$dartLoader.forceLoadModule("$clientScript");\n';
110172

173+
Future<String> _legacyLoaderSetup(String entrypoint) async {
174+
final metadataProvider = metadataProviderFor(entrypoint);
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final modulePaths = await _moduleProvider(metadataProvider);
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final scripts = <Map<String, String?>>[];
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modulePaths.forEach((name, path) {
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scripts.add(<String, String>{'src': '$path.js', 'id': name});
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});
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return '''
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$_baseUrlScript
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var scripts = ${const JsonEncoder.withIndent(" ").convert(scripts)};
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window.\$dartLoader.loadScripts(scripts);
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''';
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}
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111187
@override
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Future<String?> moduleForServerPath(String entrypoint, String serverPath) =>
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_moduleForServerPath(metadataProviderFor(entrypoint), serverPath);

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