Revert "Revert "[web] Move JS content to its own .js files (#117691)" (#120275)" (#120363)

This reverts commit 0fb4406.

Author: mdebbar

packages/flutter_tools/lib/src/artifacts.dart

@@ -9,6 +9,7 @@ import 'base/common.dart';
 import 'base/file_system.dart';
 import 'base/os.dart';
 import 'base/platform.dart';
+import 'base/user_messages.dart';
 import 'base/utils.dart';
 import 'build_info.dart';
 import 'cache.dart';
@@ -62,6 +63,9 @@ enum Artifact {
   /// Tools related to subsetting or icon font files.
   fontSubset,
   constFinder,
+
+  /// The location of file generators.
+  flutterToolsFileGenerators,
 }
 
 /// A subset of [Artifact]s that are platform and build mode independent
@@ -202,6 +206,8 @@ String? _artifactToFileName(Artifact artifact, Platform hostPlatform, [ BuildMod
       return 'font-subset$exe';
     case Artifact.constFinder:
       return 'const_finder.dart.snapshot';
+    case Artifact.flutterToolsFileGenerators:
+      return '';
   }
 }
 
@@ -525,6 +531,8 @@ class CachedArtifacts implements Artifacts {
       case Artifact.windowsCppClientWrapper:
       case Artifact.windowsDesktopPath:
         return _getHostArtifactPath(artifact, platform, mode);
+      case Artifact.flutterToolsFileGenerators:
+        return _getFileGeneratorsPath();
     }
   }
 
@@ -562,6 +570,8 @@ class CachedArtifacts implements Artifacts {
       case Artifact.windowsCppClientWrapper:
       case Artifact.windowsDesktopPath:
         return _getHostArtifactPath(artifact, platform, mode);
+      case Artifact.flutterToolsFileGenerators:
+        return _getFileGeneratorsPath();
     }
   }
 
@@ -611,6 +621,8 @@ class CachedArtifacts implements Artifacts {
       case Artifact.windowsCppClientWrapper:
       case Artifact.windowsDesktopPath:
         return _getHostArtifactPath(artifact, platform, mode);
+      case Artifact.flutterToolsFileGenerators:
+        return _getFileGeneratorsPath();
     }
   }
 
@@ -685,6 +697,8 @@ class CachedArtifacts implements Artifacts {
       case Artifact.fuchsiaFlutterRunner:
       case Artifact.fuchsiaKernelCompiler:
         throw StateError('Artifact $artifact not available for platform $platform.');
+      case Artifact.flutterToolsFileGenerators:
+        return _getFileGeneratorsPath();
     }
   }
 
@@ -952,6 +966,8 @@ class CachedLocalEngineArtifacts implements Artifacts {
       case Artifact.dart2wasmSnapshot:
       case Artifact.frontendServerSnapshotForEngineDartSdk:
         return _fileSystem.path.join(_getDartSdkPath(), 'bin', 'snapshots', artifactFileName);
+      case Artifact.flutterToolsFileGenerators:
+        return _getFileGeneratorsPath();
     }
   }
 
@@ -1099,6 +1115,7 @@ class CachedLocalWebSdkArtifacts implements Artifacts {
         case Artifact.fuchsiaFlutterRunner:
         case Artifact.fontSubset:
         case Artifact.constFinder:
+        case Artifact.flutterToolsFileGenerators:
           break;
       }
     }
@@ -1298,6 +1315,11 @@ class _TestArtifacts implements Artifacts {
     BuildMode? mode,
     EnvironmentType? environmentType,
   }) {
+    // The path to file generators is the same even in the test environment.
+    if (artifact == Artifact.flutterToolsFileGenerators) {
+      return _getFileGeneratorsPath();
+    }
+
     final StringBuffer buffer = StringBuffer();
     buffer.write(artifact);
     if (platform != null) {
@@ -1340,3 +1362,20 @@ class _TestLocalEngine extends _TestArtifacts {
   @override
   final LocalEngineInfo localEngineInfo;
 }
+
+String _getFileGeneratorsPath() {
+  final String flutterRoot = Cache.defaultFlutterRoot(
+    fileSystem: globals.localFileSystem,
+    platform: const LocalPlatform(),
+    userMessages: UserMessages(),
+  );
+  return globals.localFileSystem.path.join(
+    flutterRoot,
+    'packages',
+    'flutter_tools',
+    'lib',
+    'src',
+    'web',
+    'file_generators',
+  );
+}

packages/flutter_tools/lib/src/build_system/targets/web.dart

@@ -529,7 +529,10 @@ class WebBuiltInAssets extends Target {
 
     // Write the flutter.js file
     final File flutterJsFile = environment.outputDir.childFile('flutter.js');
-    flutterJsFile.writeAsStringSync(flutter_js.generateFlutterJsFile());
+    final String fileGeneratorsPath =
+        globals.artifacts!.getArtifactPath(Artifact.flutterToolsFileGenerators);
+    flutterJsFile.writeAsStringSync(
+        flutter_js.generateFlutterJsFile(fileGeneratorsPath));
   }
 }
 
@@ -598,7 +601,10 @@ class WebServiceWorker extends Target {
     final ServiceWorkerStrategy serviceWorkerStrategy = _serviceWorkerStrategyFromString(
       environment.defines[kServiceWorkerStrategy],
     );
+    final String fileGeneratorsPath =
+        globals.artifacts!.getArtifactPath(Artifact.flutterToolsFileGenerators);
     final String serviceWorker = generateServiceWorker(
+      fileGeneratorsPath,
       urlToHash,
       <String>[
         'main.dart.js',

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

@@ -828,7 +828,10 @@ class WebDevFS implements DevFS {
           'stack_trace_mapper.js', stackTraceMapper.readAsBytesSync());
       webAssetServer.writeFile(
           'manifest.json', '{"info":"manifest not generated in run mode."}');
-      webAssetServer.writeFile('flutter.js', flutter_js.generateFlutterJsFile());
+      final String fileGeneratorsPath = globals.artifacts!
+          .getArtifactPath(Artifact.flutterToolsFileGenerators);
+      webAssetServer.writeFile(
+          'flutter.js', flutter_js.generateFlutterJsFile(fileGeneratorsPath));
       webAssetServer.writeFile('flutter_service_worker.js',
           '// Service worker not loaded in run mode.');
       webAssetServer.writeFile(