Add a diagnostic.getServerPort analysis server request.

pkg/analysis_server/lib/src/server/http_server.dart

 // Copyright (c) 2014, 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 analysis_server.src.server.http_server;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:analysis_server/src/channel/web_socket_channel.dart';
 import 'package:analysis_server/src/socket_server.dart';
 import 'package:analysis_server/src/status/get_handler.dart';
 import 'package:analysis_server/src/status/get_handler2.dart';
 
 /**
  * Instances of the class [HttpServer] implement a simple HTTP server. The
- * primary responsibility of this server is to listen for an UPGRADE request and
- * to start an analysis server.
+ * server:
+ *
+ * - listens for an UPGRADE request in order to start an analysis server
+ * - serves diagnostic information as html pages
  */
 class HttpAnalysisServer {
   /**
    * Number of lines of print output to capture.
    */
   static const int MAX_PRINT_BUFFER_LENGTH = 1000;
 
   /**
    * An object that can handle either a WebSocket connection or a connection
    * to the client over stdio.
@@ skipping 13 matching lines @@
   /**
    * Last PRINT_BUFFER_LENGTH lines printed.
    */
   List<String> _printBuffer = <String>[];
 
   /**
    * Initialize a newly created HTTP server.
    */
   HttpAnalysisServer(this.socketServer);
 
+  /**
+   * Return the port this server is bound to.
+   */
+  Future<int> get boundPort async => (await _server)?.port;
+
   void close() {
     _server.then((HttpServer server) {
       server.close();
     });
   }
 
   /**
    * Record that the given line was printed out by the analysis server.
    */
   void recordPrint(String line) {
     _printBuffer.add(line);
     if (_printBuffer.length > MAX_PRINT_BUFFER_LENGTH) {
       _printBuffer.removeRange(
           0, _printBuffer.length - MAX_PRINT_BUFFER_LENGTH);
     }
   }
 
   /**
    * Begin serving HTTP requests over the given port.
    */
-  void serveHttp(int port) {
-    _server = HttpServer.bind(InternetAddress.LOOPBACK_IP_V4, port);
-    _server.then(_handleServer).catchError((_) {/* Ignore errors. */});
+  Future<int> serveHttp([int initialPort]) async {
+    if (_server != null) {
+      return boundPort;
+    }
+
+    try {
+      _server =
+          HttpServer.bind(InternetAddress.LOOPBACK_IP_V4, initialPort ?? 0);
+      HttpServer server = await _server;
+      _handleServer(server);
+      return server.port;
+    } catch (ignore) {
+      return null;
+    }
   }
 
   /**
    * Handle a GET request received by the HTTP server.
    */
   void _handleGetRequest(HttpRequest request) {
     if (getHandler == null) {
       if (socketServer.analysisServer.options.enableNewAnalysisDriver) {
         getHandler = new GetHandler2(socketServer, _printBuffer);
       } else {
@@ skipping 19 matching lines @@
         _returnUnknownRequest(request);
       }
     });
   }
 
   /**
    * Handle an UPGRADE request received by the HTTP server by creating and
    * running an analysis server on a [WebSocket]-based communication channel.
    */
   void _handleWebSocket(WebSocket socket) {
+    // TODO(devoncarew): This serves the analysis server over a websocket
+    // connection for historical reasons (and should probably be removed).
     socketServer.createAnalysisServer(new WebSocketServerChannel(
         socket, socketServer.instrumentationService));
   }
 
   /**
    * Return an error in response to an unrecognized request received by the HTTP
    * server.
    */
   void _returnUnknownRequest(HttpRequest request) {
     HttpResponse response = request.response;
     response.statusCode = HttpStatus.NOT_FOUND;
     response.headers.contentType =
         new ContentType("text", "plain", charset: "utf-8");
     response.write('Not found');
     response.close();
   }
 }