Add support for --pub-serve.

lib/src/runner/browser/server.dart

Index: lib/src/runner/browser/server.dart
diff --git a/lib/src/runner/browser/server.dart b/lib/src/runner/browser/server.dart
index 9730e3c2a276ca36808cccd00ca5caabc535146f..87b6ef38edb402a82d4b775dc5b36922bf1fa15b 100644
--- a/lib/src/runner/browser/server.dart
+++ b/lib/src/runner/browser/server.dart
@@ -9,6 +9,7 @@ import 'dart:convert';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
+import 'package:pool/pool.dart';
 import 'package:shelf/shelf.dart' as shelf;
 import 'package:shelf/shelf_io.dart' as shelf_io;
 import 'package:shelf_static/shelf_static.dart';
@@ -17,6 +18,8 @@ import 'package:shelf_web_socket/shelf_web_socket.dart';
 import '../../backend/suite.dart';
 import '../../util/io.dart';
 import '../../util/one_off_handler.dart';
+import '../../utils.dart';
+import '../load_exception.dart';
 import 'browser_manager.dart';
 import 'compiler_pool.dart';
 import 'chrome.dart';
@@ -31,9 +34,13 @@ class BrowserServer {
   /// compiling tests to JS. Otherwise, the package root is inferred from the
   /// location of the source file.
   ///
+  /// If [pubServeUrl] is passed, tests will be loaded from the `pub serve`
+  /// instance at that URL rather than from the filesystem.
+  ///
   /// If [color] is true, console colors will be used when compiling Dart.
-  static Future<BrowserServer> start({String packageRoot, bool color: false}) {
-    var server = new BrowserServer._(packageRoot, color);
+  static Future<BrowserServer> start({String packageRoot, Uri pubServeUrl,
+      bool color: false}) {
+    var server = new BrowserServer._(packageRoot, pubServeUrl, color);
     return server._load().then((_) => server);
   }
 
@@ -51,6 +58,8 @@ class BrowserServer {
   final _webSocketHandler = new OneOffHandler();
 
   /// The [CompilerPool] managing active instances of `dart2js`.
+  ///
+  /// This is `null` if tests are loaded from `pub serve`.
   final CompilerPool _compilers;
 
   /// The temporary directory in which compiled JS is emitted.
@@ -59,6 +68,20 @@ class BrowserServer {
   /// The package root which is passed to `dart2js`.
   final String _packageRoot;
 
+  /// The URL for the `pub serve` instance to use to load tests.
+  ///
+  /// This is `null` if tests should be compiled manually.
+  final Uri _pubServeUrl;
+
+  /// The pool of active `pub serve` compilations.
+  ///
+  /// Pub itself ensures that only one compilation runs at a time; we just use
+  /// this pool to make sure that the output is nice and linear.
+  final _pubServePool = new Pool(1);
+
+  /// The HTTP client to use when caching JS files in `pub serve`.
+  final HttpClient _http;
+
   /// The browser in which test suites are loaded and run.
   ///
   /// This is `null` until a suite is loaded.
@@ -76,7 +99,14 @@ class BrowserServer {
       }));
 
       var webSocketUrl = url.replace(scheme: 'ws', path: '/$path');
-      _browser = new Chrome(url.replace(queryParameters: {
+
+      var hostUrl = url;
+      if (_pubServeUrl != null) {
+        hostUrl = _pubServeUrl.resolve(
+            '/packages/test/src/runner/browser/static/');
+      }
+
+      _browser = new Chrome(hostUrl.replace(queryParameters: {
         'managerUrl': webSocketUrl.toString()
       }));
 
@@ -91,18 +121,27 @@ class BrowserServer {
   }
   Completer<BrowserManager> _browserManagerCompleter;
 
-  BrowserServer._(this._packageRoot, bool color)
-      : _compiledDir = Directory.systemTemp.createTempSync('test_').path,
+  BrowserServer._(this._packageRoot, Uri pubServeUrl, bool color)
+      : _pubServeUrl = pubServeUrl,
+        _compiledDir = pubServeUrl == null
+            ? Directory.systemTemp.createTempSync('test_').path
+            : null,
+        _http = pubServeUrl == null ? null : new HttpClient(),
         _compilers = new CompilerPool(color: color);
 
   /// Starts the underlying server.
   Future _load() {
-    var staticPath = p.join(libDir(packageRoot: _packageRoot),
-        'src/runner/browser/static');
     var cascade = new shelf.Cascade()
-        .add(_webSocketHandler.handler)
-        .add(createStaticHandler(staticPath, defaultDocument: 'index.html'))
-        .add(createStaticHandler(_compiledDir, defaultDocument: 'index.html'));
+        .add(_webSocketHandler.handler);
+
+    if (_pubServeUrl == null) {
+      var staticPath = p.join(libDir(packageRoot: _packageRoot),
+          'src/runner/browser/static');
+      cascade = cascade
+          .add(createStaticHandler(staticPath, defaultDocument: 'index.html'))
+          .add(createStaticHandler(_compiledDir,
+              defaultDocument: 'index.html'));
+    }
 
     return shelf_io.serve(cascade.handler, 'localhost', 0).then((server) {
       _server = server;
@@ -113,19 +152,67 @@ class BrowserServer {
   ///
   /// This will start a browser to load the suite if one isn't already running.
   Future<Suite> loadSuite(String path) {
-    return _compileSuite(path).then((dir) {
+    return new Future.sync(() {
+      if (_pubServeUrl != null) {
+
+        var suitePrefix = p.withoutExtension(p.relative(path, from: 'test')) +
+            '.browser_test';
+        var jsUrl = _pubServeUrl.resolve('$suitePrefix.dart.js');
+        return _pubServeSuite(path, jsUrl)
+            .then((_) => _pubServeUrl.resolve('$suitePrefix.html'));
+      } else {
+        return _compileSuite(path).then((dir) {
+          // Add a trailing slash because at least on Chrome, the iframe's
+          // window.location.href will do so automatically, and if that differs
+          // from the original URL communication will fail.
+          return url.resolve(
+              "/" + p.toUri(p.relative(dir, from: _compiledDir)).path + "/");
+        });
+      }
+    }).then((suiteUrl) {
       // TODO(nweiz): Don't start the browser until all the suites are compiled.
       return _browserManager.then((browserManager) {
-        // Add a trailing slash because at least on Chrome, the iframe's
-        // window.location.href will do so automatically, and if that differs
-        // from the original URL communication will fail.
-        var suiteUrl = url.resolve(
-            "/" + p.toUri(p.relative(dir, from: _compiledDir)).path + "/");
         return browserManager.loadSuite(path, suiteUrl);
       });
     });
   }
 
+  /// Loads a test suite at [path] from the `pub serve` URL [jsUrl].
+  ///
+  /// This ensures that only one suite is loaded at a time, and that any errors
+  /// are exposed as [LoadException]s.
+  Future _pubServeSuite(String path, Uri jsUrl) {
+    return _pubServePool.withResource(() {
+      var timer = new Timer(new Duration(seconds: 1), () {
+        print('"pub serve" is compiling $path...');
+      });
+
+      return _http.headUrl(jsUrl)
+          .then((request) => request.close())
+          .whenComplete(timer.cancel)
+          .catchError((error, stackTrace) {
+        if (error is! IOException) throw error;
+
+        var message = getErrorMessage(error);
+        if (error is SocketException) {
+          message = "${error.osError.message} "
+              "(errno ${error.osError.errorCode})";
+        }
+
+        throw new LoadException(path,
+            "Error getting $jsUrl: $message\n"
+            'Make sure "pub serve" is running.');
+      }).then((response) {
+        if (response.statusCode == 200) return;
+
+        throw new LoadException(path,
+            "Error getting $jsUrl: ${response.statusCode} "
+                "${response.reasonPhrase}\n"
+            'Make sure "pub serve" is serving the test/ directory.');
+      });
+    });
+  }
+
   /// Compile the test suite at [dartPath] to JavaScript.
   ///
   /// Returns a [Future] that completes to the path to the JavaScript.
@@ -154,7 +241,12 @@ class BrowserServer {
   /// Returns a [Future] that completes once the server is closed and its
   /// resources have been fully released.
   Future close() {
-    new Directory(_compiledDir).deleteSync(recursive: true);
+    if (_pubServeUrl == null) {
+      new Directory(_compiledDir).deleteSync(recursive: true);
+    } else {
+      _http.close();
+    }
+
     return _server.close().then((_) {
       if (_browserManagerCompleter == null) return null;
       return _browserManager.then((_) => _browser.close());