pkg/unittest: Add a server for serving test assets to browsers.

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
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+// Copyright (c) 2015, 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.
+
+library unittest.runner.browser.server;
+
+import 'dart:async';
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:path/path.dart' as p;
+import 'package:shelf/shelf.dart' as shelf;
+import 'package:shelf/shelf_io.dart' as shelf_io;
+import 'package:shelf_static/shelf_static.dart';
+import 'package:shelf_web_socket/shelf_web_socket.dart';
+
+import '../../backend/suite.dart';
+import '../../util/io.dart';
+import '../../util/one_off_handler.dart';
+import 'browser_manager.dart';
+import 'compiler_pool.dart';
+import 'chrome.dart';
+
+/// A server that serves JS-compiled tests to browsers.
+///
+/// A test suite may be loaded for a given file using [loadSuite].
+class BrowserServer {
+  /// Starts the server.
+  ///
+  /// If [packageRoot] is passed, it's used for all package imports when
+  /// compiling tests to JS. Otherwise, the package root is inferred from the
+  /// location of the source file.
+  static Future<BrowserServer> start({String packageRoot}) {
+    var server = new BrowserServer._(packageRoot);
+    return server._load().then((_) => server);
+  }
+
+  /// The underlying HTTP server.
+  HttpServer _server;
+
+  /// The URL for this server.
+  Uri get url => baseUrlForAddress(_server.address, _server.port);
+
+  /// a [OneOffHandler] for servicing WebSocket connections for
+  /// [BrowserManager]s.
+  ///
+  /// This is one-off because each [BrowserManager] can only connect to a single
+  /// WebSocket,
+  final _webSocketHandler = new OneOffHandler();
+
+  /// The [CompilerPool] managing active instances of `dart2js`.
+  final _compilers = new CompilerPool();
+
+  /// The temporary directory in which compiled JS is emitted.
+  final String _compiledDir;
+
+  /// The package root which is passed to `dart2js`.
+  final String _packageRoot;
+
+  /// The browser in which test suites are loaded and run.
+  ///
+  /// This is `null` until a suite is loaded.
+  Chrome _browser;
+
+  /// A future that will complete to the [BrowserManager] for [_browser].
+  ///
+  /// The first time this is called, it will start both the browser and the
+  /// browser manager. Any further calls will return the existing manager.
+  Future<BrowserManager> get _browserManager {
+    if (_browserManagerCompleter == null) {
+      _browserManagerCompleter = new Completer();
+      var path = _webSocketHandler.create(webSocketHandler((webSocket) {
+        _browserManagerCompleter.complete(new BrowserManager(webSocket));
+      }));
+
+      var webSocketUrl = url.replace(scheme: 'ws', path: '/$path');
+      _browser = new Chrome(url.replace(queryParameters: {
+        'managerUrl': webSocketUrl.toString()
+      }));
+
+      // TODO(nweiz): Gracefully handle the browser being killed before the
+      // tests complete.
+      _browser.onExit.catchError((error, stackTrace) {
+        if (_browserManagerCompleter.isCompleted) return;
+        _browserManagerCompleter.completeError(error, stackTrace);
+      });
+    }
+    return _browserManagerCompleter.future;
+  }
+  Completer<BrowserManager> _browserManagerCompleter;
+
+  BrowserServer._(this._packageRoot)
+      : _compiledDir = Directory.systemTemp.createTempSync('unittest_').path;
+
+  /// 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'));
+
+    return shelf_io.serve(cascade.handler, 'localhost', 0).then((server) {
+      _server = server;
+    });
+  }
+
+  /// Loads the test suite at [path].
+  ///
+  /// 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) {
+      // 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);
+      });
+    });
+  }
+
+  /// Compile the test suite at [dartPath] to JavaScript.
+  ///
+  /// Returns a [Future] that completes to the path to the JavaScript.
+  Future<String> _compileSuite(String dartPath) {
+    var dir = new Directory(_compiledDir).createTempSync('test_').path;
+    var jsPath = p.join(dir, p.basename(dartPath) + ".js");
+    return _compilers.compile(dartPath, jsPath,
+            packageRoot: packageRootFor(dartPath, _packageRoot))
+        .then((_) {
+      // TODO(nweiz): support user-authored HTML files.
+      new File(p.join(dir, "index.html")).writeAsStringSync('''
+<!DOCTYPE html>
+<html>
+<head>
+  <title>${HTML_ESCAPE.convert(dartPath)} Test</title>
+  <script src="${HTML_ESCAPE.convert(p.basename(jsPath))}"></script>
+</head>
+</html>
+''');
+      return dir;
+    });
+  }
+
+  /// Closes the server and releases all its resources.
+  ///
+  /// 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);
+    return _server.close().then((_) {
+      if (_browserManagerCompleter == null) return null;
+      return _browserManager.then((_) => _browser.close());
+    });
+  }
+}