Add a basic serve mode, which blocks all requests on ongoing builds.

lib/src/generate/build.dart

@@ -5,15 +5,16 @@ import 'dart:async';
 import 'dart:io';
 
 import 'package:logging/logging.dart';
+import 'package:shelf/shelf.dart';
 
-import '../asset/cache.dart';
-import '../asset/file_based.dart';
 import '../asset/reader.dart';
 import '../asset/writer.dart';
 import '../package_graph/package_graph.dart';
+import '../server/server.dart';
 import 'build_impl.dart';
 import 'build_result.dart';
 import 'directory_watcher_factory.dart';
+import 'options.dart';
 import 'phase.dart';
 import 'watch_impl.dart';
 
@@ -43,15 +44,13 @@ Future<BuildResult> build(List<List<Phase>> phaseGroups,
     Level logLevel,
     onLog(LogRecord),
     Stream terminateEventStream}) async {
-  var logListener = _setupLogging(logLevel: logLevel, onLog: onLog);
-  packageGraph ??= new PackageGraph.forThisPackage();
-  var cache = new AssetCache();
-  reader ??=
-      new CachedAssetReader(cache, new FileBasedAssetReader(packageGraph));
-  writer ??=
-      new CachedAssetWriter(cache, new FileBasedAssetWriter(packageGraph));
-
-  var buildImpl = new BuildImpl(reader, writer, packageGraph, phaseGroups);
+  var options = new BuildOptions(
+      packageGraph: packageGraph,
+      reader: reader,
+      writer: writer,
+      logLevel: logLevel,
+      onLog: onLog);
+  var buildImpl = new BuildImpl(options, phaseGroups);
 
   /// Run the build!
   var futureResult = buildImpl.runBuild();
@@ -64,7 +63,7 @@ Future<BuildResult> build(List<List<Phase>> phaseGroups,
 
   var result = await futureResult;
   listener.cancel();
-  logListener.cancel();
+  options.logListener.cancel();
   return result;
 }
 
@@ -89,28 +88,72 @@ Stream<BuildResult> watch(List<List<Phase>> phaseGroups,
     AssetWriter writer,
     Level logLevel,
     onLog(LogRecord),
-    Duration debounceDelay: const Duration(milliseconds: 250),
+    Duration debounceDelay,
     DirectoryWatcherFactory directoryWatcherFactory,
     Stream terminateEventStream}) {
-  // We never cancel this listener in watch mode, because we never exit unless
-  // forced to.
-  var logListener = _setupLogging(logLevel: logLevel, onLog: onLog);
-  packageGraph ??= new PackageGraph.forThisPackage();
-  var cache = new AssetCache();
-  reader ??=
-      new CachedAssetReader(cache, new FileBasedAssetReader(packageGraph));
-  writer ??=
-      new CachedAssetWriter(cache, new FileBasedAssetWriter(packageGraph));
-  directoryWatcherFactory ??= defaultDirectoryWatcherFactory;
-  var watchImpl = new WatchImpl(directoryWatcherFactory, debounceDelay, reader,
-      writer, packageGraph, phaseGroups);
+  var options = new BuildOptions(
+      packageGraph: packageGraph,
+      reader: reader,
+      writer: writer,
+      logLevel: logLevel,
+      onLog: onLog,
+      debounceDelay: debounceDelay,
+      directoryWatcherFactory: directoryWatcherFactory);
+  var watchImpl = new WatchImpl(options, phaseGroups);
+
+  var resultStream = watchImpl.runWatch();
+
+  // Stop doing new builds when told to terminate.
+  _setupTerminateLogic(terminateEventStream, () async {
+    await watchImpl.terminate();
+    options.logListener.cancel();
+  });
+
+  return resultStream;
+}
+
+/// Same as [watch], except it also provides a server.
+///
+/// This server will block all requests if a build is current in process.
+///
+/// By default a static server will be set up to serve [directory] at
+/// [address]:[port], but instead a [requestHandler] may be provided for custom
+/// behavior.
+Stream<BuildResult> serve(List<List<Phase>> phaseGroups,
+    {PackageGraph packageGraph,
+    AssetReader reader,
+    AssetWriter writer,
+    Level logLevel,
+    onLog(LogRecord),
+    Duration debounceDelay,
+    DirectoryWatcherFactory directoryWatcherFactory,
+    Stream terminateEventStream,
+    String directory,
+    String address,
+    int port,
+    Handler requestHandler}) {
+  var options = new BuildOptions(
+      packageGraph: packageGraph,
+      reader: reader,
+      writer: writer,
+      logLevel: logLevel,
+      onLog: onLog,
+      debounceDelay: debounceDelay,
+      directoryWatcherFactory: directoryWatcherFactory,
+      directory: directory,
+      address: address,
+      port: port);
+  var watchImpl = new WatchImpl(options, phaseGroups);
 
   var resultStream = watchImpl.runWatch();
+  var serverStarted = startServer(watchImpl, options);
 
   // Stop doing new builds when told to terminate.
   _setupTerminateLogic(terminateEventStream, () async {
     await watchImpl.terminate();
-    logListener.cancel();
+    await serverStarted;
+    await stopServer();
+    options.logListener.cancel();
   });
 
   return resultStream;
@@ -135,10 +178,3 @@ StreamSubscription _setupTerminateLogic(
   });
   return terminateListener;
 }
-
-StreamSubscription _setupLogging({Level logLevel, onLog(LogRecord)}) {
-  logLevel ??= Level.INFO;
-  Logger.root.level = logLevel;
-  onLog ??= stdout.writeln;
-  return Logger.root.onRecord.listen(onLog);
-}

lib/src/generate/build_impl.dart

@@ -25,6 +25,7 @@ import '../package_graph/package_graph.dart';
 import 'build_result.dart';
 import 'exceptions.dart';
 import 'input_set.dart';
+import 'options.dart';
 import 'phase.dart';
 
 /// Class which manages running builds.
@@ -42,7 +43,10 @@ class BuildImpl {
 
   bool _isFirstBuild = true;
 
-  BuildImpl(this._reader, this._writer, this._packageGraph, this._phaseGroups);
+  BuildImpl(BuildOptions options, this._phaseGroups)
+      : _reader = options.reader,
+        _writer = options.writer,
+        _packageGraph = options.packageGraph;
 
   /// Runs a build
   ///

lib/src/generate/options.dart

@@ -0,0 +1,69 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// 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:async';
+import 'dart:io';
+
+import 'package:logging/logging.dart';
+import 'package:shelf/shelf.dart';
+import 'package:shelf_static/shelf_static.dart';
+
+import '../asset/cache.dart';
+import '../asset/file_based.dart';
+import '../asset/reader.dart';
+import '../asset/writer.dart';
+import '../package_graph/package_graph.dart';
+import 'directory_watcher_factory.dart';
+
+/// Manages setting up consistent defaults for all options and build modes.
+class BuildOptions {
+  /// Build mode options.
+  StreamSubscription logListener;
+  PackageGraph packageGraph;
+  AssetReader reader;
+  AssetWriter writer;
+
+  /// Watch mode options.
+  Duration debounceDelay;
+  DirectoryWatcherFactory directoryWatcherFactory;
+
+  /// Server options.
+  int port;
+  String address;
+  String directory;
+  Handler requestHandler;
+
+  BuildOptions(
+      {this.debounceDelay,
+      this.directoryWatcherFactory,
+      Level logLevel,
+      onLog(LogRecord),
+      this.packageGraph,
+      this.reader,
+      this.writer,
+      this.directory,
+      this.address,
+      this.port,
+      this.requestHandler}) {
+    /// Set up logging
+    logLevel ??= Level.INFO;
+    Logger.root.level = logLevel;
+    onLog ??= stdout.writeln;
+    logListener = Logger.root.onRecord.listen(onLog);
+
+    /// Set up other defaults.
+    address ??= 'localhost';
+    directory ??= '.';
+    port ??= 8000;
+    requestHandler ??= createStaticHandler(directory,
+        defaultDocument: 'index.html', listDirectories: true);
+    debounceDelay ??= const Duration(milliseconds: 250);
+    packageGraph ??= new PackageGraph.forThisPackage();
+    var cache = new AssetCache();
+    reader ??=
+        new CachedAssetReader(cache, new FileBasedAssetReader(packageGraph));
+    writer ??=
+        new CachedAssetWriter(cache, new FileBasedAssetWriter(packageGraph));
+    directoryWatcherFactory ??= defaultDirectoryWatcherFactory;
+  }
+}

lib/src/generate/watch_impl.dart

@@ -8,14 +8,14 @@ import 'package:path/path.dart' as path;
 import 'package:watcher/watcher.dart';
 
 import '../asset/id.dart';
-import '../asset/reader.dart';
 import '../asset/writer.dart';
 import '../asset_graph/graph.dart';
 import '../asset_graph/node.dart';
 import '../package_graph/package_graph.dart';
 import 'build_impl.dart';
 import 'build_result.dart';
 import 'directory_watcher_factory.dart';
+import 'options.dart';
 import 'phase.dart';
 
 /// Watches all inputs for changes, and uses a [BuildImpl] to rerun builds as
@@ -47,6 +47,7 @@ class WatchImpl {
 
   /// A future that completes when the current build is done.
   Future _currentBuild;
+  Future get currentBuild => _currentBuild;
 
   /// Whether or not another build is scheduled.
   bool _nextBuildScheduled;
@@ -60,16 +61,12 @@ class WatchImpl {
   /// Whether we are in the process of terminating.
   bool _terminating = false;
 
-  WatchImpl(
-      this._directoryWatcherFactory,
-      this._debounceDelay,
-      AssetReader reader,
-      AssetWriter writer,
-      PackageGraph packageGraph,
-      List<List<Phase>> phaseGroups)
-      : _packageGraph = packageGraph,
-        _writer = writer,
-        _buildImpl = new BuildImpl(reader, writer, packageGraph, phaseGroups);
+  WatchImpl(BuildOptions options, List<List<Phase>> phaseGroups)
+      : _directoryWatcherFactory = options.directoryWatcherFactory,
+        _debounceDelay = options.debounceDelay,
+        _writer = options.writer,
+        _packageGraph = options.packageGraph,
+        _buildImpl = new BuildImpl(options, phaseGroups);
 
   /// Completes after the current build is done, and stops further builds from
   /// happening.

lib/src/server/server.dart

@@ -0,0 +1,48 @@
+// Copyright (c) 2016, the Dart project authors.  Please see the AUTHORS file
+// 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:async';
+import 'dart:io';
+import 'package:shelf/shelf.dart';
+import 'package:shelf/shelf_io.dart';
+import 'package:shelf_static/shelf_static.dart';
+
+import '../generate/options.dart';
+import '../generate/watch_impl.dart';
+
+/// The actual [HttpServer] in use.
+Future<HttpServer> _futureServer;
+
+/// Public for testing purposes only :(. This file is not directly exported
+/// though so it is effectively package private.
+Handler blockingHandler;
+
+/// Starts a server which blocks on any ongoing builds.
+Future<HttpServer> startServer(WatchImpl watchImpl, BuildOptions options) {
+  if (_futureServer != null) {
+    throw new StateError('Server already running.');
+  }
+
+  try {
+    blockingHandler = (Request request) async {
+      if (watchImpl.currentBuild != null) await watchImpl.currentBuild;
+      return options.requestHandler(request);
+    };
+    _futureServer = serve(blockingHandler, options.address, options.port);
+    return _futureServer;
+  } catch (e, s) {
+    stderr.writeln('Error setting up server: $e\n\n$s');
+    return new Future.value(null);
+  }
+}
+
+Future stopServer() {
+  if (_futureServer == null) {
+    throw new StateError('Server not running.');
+  }
+  return _futureServer.then((server) {
+    server.close();
+    _futureServer = null;
+    blockingHandler = null;
+  });
+}

pubspec.yaml

@@ -14,6 +14,8 @@ dependencies:
   logging: ^0.11.2
   glob: ^1.1.0
   path: ^1.1.0
+  shelf: ^0.6.5
+  shelf_static: ^0.2.3
   source_maps: '>=0.9.4 <0.11.0'
   source_span: '>=1.0.0 <2.0.0'
   stack_trace: ^1.6.0

test/common/common.dart

@@ -13,6 +13,7 @@ import 'in_memory_writer.dart';
 
 export 'assets.dart';
 export 'copy_builder.dart';
+export 'fake_watcher.dart';
 export 'file_combiner_builder.dart';
 export 'in_memory_reader.dart';
 export 'in_memory_writer.dart';
@@ -51,3 +52,17 @@ void checkOutputs(Map<String, String> outputs, BuildResult result,
         reason: 'Unexpected outputs found `$remainingOutputIds`.');
   }
 }
+
+Future<BuildResult> nextResult(results) {
+  var done = new Completer();
+  var startingLength = results.length;
+  () async {
+    while (results.length == startingLength) {
+      await wait(10);
+    }
+    expect(results.length, startingLength + 1,
+        reason: 'Got two build results but only expected one');
+    done.complete(results.last);
+  }();
+  return done.future;
+}

test/common/copy_builder.dart

@@ -20,13 +20,20 @@ class CopyBuilder implements Builder {
   /// asset.
   final AssetId copyFromAsset;
 
+  /// No `build` step will complete until this future completes. It may be
+  /// re-assigned in between builds.
+  Future blockUntil;
+
   CopyBuilder(
       {this.numCopies: 1,
       this.extension: 'copy',
       this.outputPackage,
-      this.copyFromAsset});
+      this.copyFromAsset,
+      this.blockUntil});
 
   Future build(BuildStep buildStep) async {
+    if (blockUntil != null) await blockUntil;
+
     var ids = declareOutputs(buildStep.input.id);
     for (var id in ids) {
       var content = copyFromAsset == null