adding an option to redirect all not found to a specific asset

build_runner/CHANGELOG.md

@@ -8,9 +8,10 @@
 
 - Upgrade to `frontend_service_client` version 3.
 
-## 2.3.0
-
+## 2.3.3-dev
 - Add `-d` as a shorthand for `--delete-conflicting-outputs`.
+- Added a flag to redirect all not found to a specific 
+  asset: ` not-found-defaults-to`
 
 ## 2.2.1
 

build_runner/lib/src/daemon/asset_server.dart

@@ -34,7 +34,7 @@ class AssetServer {
     var cascade = Cascade().add((_) async {
       await builder.building;
       return Response.notFound('');
-    }).add(AssetHandler(builder.reader, rootPackage).handle);
+    }).add(AssetHandler(builder.reader, rootPackage, null).handle);
 
     var pipeline = Pipeline();
     if (options.logRequests) {

build_runner/lib/src/entrypoint/options.dart

@@ -26,6 +26,7 @@ const liveReloadOption = 'live-reload';
 const logPerformanceOption = 'log-performance';
 const logRequestsOption = 'log-requests';
 const lowResourcesModeOption = 'low-resources-mode';
+const notFoundDefaultsToOption = 'not-found-defaults-to';
 const outputOption = 'output';
 const releaseOption = 'release';
 const trackPerformanceOption = 'track-performance';
@@ -276,41 +277,45 @@ class ServeOptions extends WatchOptions {
   final bool logRequests;
   final List<ServeTarget> serveTargets;
 
-  ServeOptions._({
-    required this.hostName,
-    required this.buildUpdates,
-    required this.logRequests,
-    required this.serveTargets,
-    required Set<BuildFilter> buildFilters,
-    required bool deleteFilesByDefault,
-    required bool enableLowResourcesMode,
-    required String? configKey,
-    required Set<BuildDirectory> buildDirs,
-    required bool outputSymlinksOnly,
-    required bool trackPerformance,
-    required bool skipBuildScriptCheck,
-    required bool verbose,
-    required Map<String, Map<String, dynamic>> builderConfigOverrides,
-    required bool isReleaseBuild,
-    required String? logPerformanceDir,
-    required bool usePollingWatcher,
-    required List<String> enableExperiments,
-  }) : super._(
-          buildFilters: buildFilters,
-          deleteFilesByDefault: deleteFilesByDefault,
-          enableLowResourcesMode: enableLowResourcesMode,
-          configKey: configKey,
-          buildDirs: buildDirs,
-          outputSymlinksOnly: outputSymlinksOnly,
-          trackPerformance: trackPerformance,
-          skipBuildScriptCheck: skipBuildScriptCheck,
-          verbose: verbose,
-          builderConfigOverrides: builderConfigOverrides,
-          isReleaseBuild: isReleaseBuild,
-          logPerformanceDir: logPerformanceDir,
-          usePollingWatcher: usePollingWatcher,
-          enableExperiments: enableExperiments,
-        );
+  // An [AssetId] path to redirect when the file is not found by
+  // the web server
+  final String? notFoundDefaultsTo;
+
+  ServeOptions._(
+      {required this.hostName,
+      required this.buildUpdates,
+      required this.logRequests,
+      required this.serveTargets,
+      required Set<BuildFilter> buildFilters,
+      required bool deleteFilesByDefault,
+      required bool enableLowResourcesMode,
+      required String? configKey,
+      required Set<BuildDirectory> buildDirs,
+      required bool outputSymlinksOnly,
+      required bool trackPerformance,
+      required bool skipBuildScriptCheck,
+      required bool verbose,
+      required Map<String, Map<String, dynamic>> builderConfigOverrides,
+      required bool isReleaseBuild,
+      required String? logPerformanceDir,
+      required bool usePollingWatcher,
+      required List<String> enableExperiments,
+      required this.notFoundDefaultsTo})
+      : super._(
+            buildFilters: buildFilters,
+            deleteFilesByDefault: deleteFilesByDefault,
+            enableLowResourcesMode: enableLowResourcesMode,
+            configKey: configKey,
+            buildDirs: buildDirs,
+            outputSymlinksOnly: outputSymlinksOnly,
+            trackPerformance: trackPerformance,
+            skipBuildScriptCheck: skipBuildScriptCheck,
+            verbose: verbose,
+            builderConfigOverrides: builderConfigOverrides,
+            isReleaseBuild: isReleaseBuild,
+            logPerformanceDir: logPerformanceDir,
+            usePollingWatcher: usePollingWatcher,
+            enableExperiments: enableExperiments);
 
   factory ServeOptions.fromParsedArgs(ArgResults argResults,
       Iterable<String> positionalArgs, String rootPackage, Command command) {
@@ -381,6 +386,7 @@ class ServeOptions extends WatchOptions {
       logPerformanceDir: argResults[logPerformanceOption] as String?,
       usePollingWatcher: argResults[usePollingWatcherOption] as bool,
       enableExperiments: argResults[enableExperimentOption] as List<String>,
+      notFoundDefaultsTo: argResults[notFoundDefaultsToOption] as String?,
     );
   }
 }

build_runner/lib/src/entrypoint/serve.dart

@@ -31,7 +31,9 @@ class ServeCommand extends WatchCommand {
       ..addFlag(liveReloadOption,
           defaultsTo: false,
           negatable: false,
-          help: 'Enables automatic page reloading on rebuilds. ');
+          help: 'Enables automatic page reloading on rebuilds. ')
+      ..addOption(notFoundDefaultsToOption,
+          help: 'Redirect not found to a specific asset.');
   }
 
   @override
@@ -98,6 +100,7 @@ class ServeCommand extends WatchCommand {
       logPerformanceDir: options.logPerformanceDir,
       directoryWatcherFactory: options.directoryWatcherFactory,
       buildFilters: options.buildFilters,
+      notFoundDefaultsTo: options.notFoundDefaultsTo
     );
 
     servers.forEach((target, server) {

build_runner/lib/src/generate/build.dart

@@ -165,7 +165,8 @@ Future<ServeHandler> watch(List<BuilderApplication> builders,
         bool? isReleaseBuild,
         Map<String, Map<String, dynamic>>? builderConfigOverrides,
         String? logPerformanceDir,
-        Set<BuildFilter>? buildFilters}) =>
+        Set<BuildFilter>? buildFilters,
+        String? notFoundDefaultsTo}) =>
     watch_impl.watch(
       builders,
       assumeTty: assumeTty,
@@ -190,4 +191,5 @@ Future<ServeHandler> watch(List<BuilderApplication> builders,
       isReleaseBuild: isReleaseBuild,
       logPerformanceDir: logPerformanceDir,
       buildFilters: buildFilters,
+      notFoundDefaultsTo: notFoundDefaultsTo
     );

build_runner/lib/src/generate/watch_impl.dart

@@ -55,6 +55,7 @@ Future<ServeHandler> watch(
   bool? isReleaseBuild,
   String? logPerformanceDir,
   Set<BuildFilter>? buildFilters,
+  String? notFoundDefaultsTo
 }) async {
   builderConfigOverrides ??= const {};
   buildDirs ??= <BuildDirectory>{};
@@ -105,7 +106,8 @@ Future<ServeHandler> watch(
           .any((target) => target.outputLocation?.path.isNotEmpty ?? false),
       buildDirs,
       buildFilters,
-      isReleaseMode: isReleaseBuild ?? false);
+      isReleaseMode: isReleaseBuild ?? false,
+      notFoundDefaultsTo: notFoundDefaultsTo);
 
   unawaited(watch.buildResults.drain().then((_) async {
     await terminator.cancel();
@@ -134,7 +136,8 @@ WatchImpl _runWatch(
         bool willCreateOutputDirs,
         Set<BuildDirectory> buildDirs,
         Set<BuildFilter> buildFilters,
-        {bool isReleaseMode = false}) =>
+        {bool isReleaseMode = false,
+        String? notFoundDefaultsTo}) =>
     WatchImpl(
         options,
         environment,
@@ -146,7 +149,8 @@ WatchImpl _runWatch(
         willCreateOutputDirs,
         buildDirs,
         buildFilters,
-        isReleaseMode: isReleaseMode);
+        isReleaseMode: isReleaseMode,
+        notFoundDefaultsTo: notFoundDefaultsTo);
 
 class WatchImpl implements BuildState {
   BuildImpl? _build;
@@ -172,6 +176,9 @@ class WatchImpl implements BuildState {
   /// The [PackageGraph] for the current program.
   final PackageGraph packageGraph;
 
+  // An asset path to redirect when the file is not found by the web server
+  final String? notFoundDefaultsTo;
+
   /// The directories to build upon file changes and where to output them.
   final Set<BuildDirectory> _buildDirs;
 
@@ -200,7 +207,7 @@ class WatchImpl implements BuildState {
       this._willCreateOutputDirs,
       this._buildDirs,
       this._buildFilters,
-      {bool isReleaseMode = false})
+      {bool isReleaseMode = false, this.notFoundDefaultsTo})
       : _debounceDelay = options.debounceDelay,
         packageGraph = options.packageGraph {
     buildResults = _run(

build_runner/lib/src/server/server.dart

@@ -47,8 +47,16 @@ ServeHandler createServeHandler(WatchImpl watch) {
   var rootPackage = watch.packageGraph.root.name;
   var assetGraphHanderCompleter = Completer<AssetGraphHandler>();
   var assetHandlerCompleter = Completer<AssetHandler>();
+
   watch.reader.then((reader) async {
-    assetHandlerCompleter.complete(AssetHandler(reader, rootPackage));
+    final notFoundDefaultsToPath = watch.notFoundDefaultsTo;
+    final notFoundDefaultsTo =
+        notFoundDefaultsToPath != null && notFoundDefaultsToPath.isNotEmpty
+            ? AssetId(rootPackage, notFoundDefaultsToPath)
+            : null;
+
+    assetHandlerCompleter
+        .complete(AssetHandler(reader, rootPackage, notFoundDefaultsTo));
     assetGraphHanderCompleter
         .complete(AssetGraphHandler(reader, rootPackage, watch.assetGraph!));
   }).catchError((_) {}); // These errors are separately handled.
@@ -300,10 +308,11 @@ window.\$dartLoader.forceLoadModule('packages/build_runner/src/server/build_upda
 class AssetHandler {
   final FinalizedReader _reader;
   final String _rootPackage;
+  final AssetId? notFoundDefaultsTo;
 
   final _typeResolver = MimeTypeResolver();
 
-  AssetHandler(this._reader, this._rootPackage);
+  AssetHandler(this._reader, this._rootPackage, this.notFoundDefaultsTo);
 
   Future<shelf.Response> handle(shelf.Request request, {String rootDir = ''}) =>
       (request.url.path.endsWith('/') || request.url.path.isEmpty)
@@ -332,6 +341,18 @@ class AssetHandler {
                 return shelf.Response.notFound(
                     await _findDirectoryList(assetId));
               }
+
+              final notFoundDefaultsTo = this.notFoundDefaultsTo;
+
+              if (notFoundDefaultsTo != null) {
+                final pathSegments = assetId.pathSegments;
+
+                if (!pathSegments.contains('package') &&
+                    !pathSegments.contains('lib')) {
+                  return _handle(request, notFoundDefaultsTo);
+                }
+              }
+
               return shelf.Response.notFound('Not Found');
             default:
               return shelf.Response.notFound('Not Found');

build_runner/test/server/serve_handler_test.dart

@@ -26,6 +26,7 @@ import 'package:web_socket_channel/web_socket_channel.dart';
 
 void main() {
   late ServeHandler serveHandler;
+  late ServeHandler serveSpaHandler;
   late InMemoryRunnerAssetReader reader;
   late MockWatchImpl watchImpl;
   late AssetGraph assetGraph;
@@ -46,6 +47,9 @@ void main() {
         packageGraph,
         assetGraph);
     serveHandler = createServeHandler(watchImpl);
+
+    watchImpl.notFoundDefaultsTo = 'web/index.html';
+    serveSpaHandler = createServeHandler(watchImpl);
     watchImpl
         .addFutureResult(Future.value(BuildResult(BuildStatus.success, [])));
   });
@@ -66,6 +70,13 @@ void main() {
     expect(await response.readAsString(), 'content');
   });
 
+  test('retrieve default asset when not found', () async {
+    _addSource('a|web/index.html', 'content');
+    var response = await serveSpaHandler.handlerFor('web')(
+        Request('GET', Uri.parse('http://server.com/foo.html')));
+    expect(await response.readAsString(), 'content');
+  });
+
   test('caching with etags works', () async {
     _addSource('a|web/index.html', 'content');
     var handler = serveHandler.handlerFor('web');
@@ -450,14 +461,17 @@ class MockWatchImpl implements WatchImpl {
 
   Future<BuildResult>? _currentBuild;
 
+  @override
+  String? notFoundDefaultsTo;
+
   @override
   Future<BuildResult>? get currentBuild => _currentBuild;
   @override
   set currentBuild(Future<BuildResult>? _) =>
       throw UnsupportedError('unsupported!');
 
   final _futureBuildResultsController = StreamController<Future<BuildResult>>();
-  final _buildResultsController = StreamController<BuildResult>();
+  final _buildResultsController = StreamController<BuildResult>.broadcast();
 
   @override
   Stream<BuildResult> get buildResults => _buildResultsController.stream;
@@ -475,7 +489,8 @@ class MockWatchImpl implements WatchImpl {
     _futureBuildResultsController.add(result);
   }
 
-  MockWatchImpl(this.reader, this.packageGraph, this.assetGraph) {
+  MockWatchImpl(this.reader, this.packageGraph, this.assetGraph,
+      {this.notFoundDefaultsTo}) {
     var firstBuild = Completer<BuildResult>();
     _currentBuild = firstBuild.future;
     _futureBuildResultsController.stream.listen((futureBuildResult) {