Set isWindows to false by default in DDC's bootstrapper for DDC-compiled apps (#4383)

This was causing library maps in DDC's library loader to have both `/` and `\`, invalidating lookups on Windows. We could multiplex between platforms, but sticking to `/` is easier.

Related: dart-lang/sdk#62824

Author: Markzipan

build_runner/test/integration_tests/watch_command_test.dart

@@ -11,7 +11,7 @@ import 'package:test/test.dart';
 import '../common/common.dart';
 
 void main() async {
-  test('watch command', () async {
+  test('watch command', timeout: const Timeout.factor(4), () async {
     final pubspecs = await Pubspecs.load();
     final tester = BuildRunnerTester(pubspecs);
 

build_web_compilers/CHANGELOG.md

@@ -1,3 +1,6 @@
+## 4.4.15
+- Normalize URIs in DDC's bootstrapper on Windows to always use forward slashes when running with the DDC Library Bundle module system.
+
 ## 4.4.14
 - Update DDC Library Bundle to use path-resolvable module names for sourcemap IDs.
 

build_web_compilers/lib/src/dev_compiler_bootstrap.dart

@@ -5,7 +5,6 @@
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
-import 'dart:io';
 
 import 'package:build/build.dart';
 import 'package:build_modules/build_modules.dart';
@@ -170,7 +169,6 @@ $librariesString
           'packages/build_web_compilers/src/dev_compiler/ddc_module_loader.js',
       mainBoostrapperUrl: bootstrapModuleName,
       mapperUrl: stackTraceMapperPath,
-      isWindows: Platform.isWindows,
       scriptIdsToPath: modulePaths,
     );
     bootstrapEndContent = generateDDCLibraryBundleOnLoadEndBootstrap();
@@ -689,7 +687,6 @@ String generateDDCLibraryBundleBootstrapScript({
   required String ddcModuleLoaderUrl,
   required String mainBoostrapperUrl,
   required String mapperUrl,
-  required bool isWindows,
   required Map<String, String> scriptIdsToPath,
 }) {
   final scriptsJs = StringBuffer();
@@ -753,8 +750,8 @@ $_simpleLoaderScript
     let scripts = [${scriptsJs.toString()}];
 
     let loadConfig = new window.\$dartLoader.LoadConfiguration();
-    // TODO(srujzs): Verify this is sufficient for Windows.
-    loadConfig.isWindows = $isWindows;
+    // `isWindows` must be false to avoid appending backlashes to paths.
+    loadConfig.isWindows = false;
     loadConfig.root = trimmedDirectory;
     loadConfig.bootstrapScript = scripts[scripts.length - 1];
 

build_web_compilers/pubspec.yaml

@@ -1,5 +1,5 @@
 name: build_web_compilers
-version: 4.4.14
+version: 4.4.15
 description: Builder implementations wrapping the dart2js and DDC compilers.
 repository: https://github.com/dart-lang/build/tree/master/build_web_compilers
 resolution: workspace

build_web_compilers/test/ddc_library_bundle_bootstrap_test.dart

@@ -119,6 +119,7 @@ void main() {
               // Imports the dart sdk.
               contains('"id": "dart_sdk"'),
               isNot(contains('lib/a')),
+              contains('loadConfig.isWindows = false;'),
             ]),
           ),
           'a|web/index.digests': decodedMatches(contains('packages/')),