Add a "--log" option to analysis server to dump log messages to a file.

pkg/analysis_server/lib/driver.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 driver;
 
 import 'dart:io';
 
 import 'package:analysis_server/http_server.dart';
 import 'package:analysis_server/src/socket_server.dart';
 import 'package:analysis_server/stdio_server.dart';
 import 'package:args/args.dart';
+import 'package:logging/logging.dart';
 
 /**
  * The [Driver] class represents a single running instance of the analysis
  * server application.  It is responsible for parsing command line options
  * and starting the HTTP and/or stdio servers.
  */
 class Driver {
   /**
    * The name of the application that is used to start a server.
    */
   static const BINARY_NAME = 'server';
 
   /**
    * The name of the option used to print usage information.
    */
   static const String HELP_OPTION = "help";
 
   /**
    * The name of the option used to specify the port to which the server will
    * connect.
    */
   static const String PORT_OPTION = "port";
 
+  /**
+   * The name of the option used to specify the log file.
+   */
+  static const String LOG_FILE_OPTION = "log";
+
   SocketServer socketServer = new SocketServer();
 
   HttpAnalysisServer httpServer;
 
   StdioAnalysisServer stdioServer;
 
   Driver() {
     httpServer = new HttpAnalysisServer(socketServer);
     stdioServer = new StdioAnalysisServer(socketServer);
   }
 
   /**
    * Use the given command-line arguments to start this server.
    */
   void start(List<String> args) {
     ArgParser parser = new ArgParser();
     parser.addFlag(HELP_OPTION, help:
         "print this help message without starting a server", defaultsTo: false,
         negatable: false);
     parser.addOption(PORT_OPTION, help:
         "[port] the port on which the server will listen");
+    parser.addOption(LOG_FILE_OPTION, help:
+        "[path] file to log debugging messages to");
 
     ArgResults results = parser.parse(args);
     if (results[HELP_OPTION]) {
       _printUsage(parser);
       return;
     }
+    if (results[LOG_FILE_OPTION] != null) {
+      try {
+        File file = new File(results[LOG_FILE_OPTION]);
+        IOSink sink = file.openWrite();
+        Logger.root.onRecord.listen((LogRecord record) {
+          sink.writeln(record);

[Brian Wilkerson, 2014/07/01 17:30:01]

Where do we close the file?

[Paul Berry, 2014/07/01 17:51:12]

We just let the OS close it for us when the process terminates.  I considered
closing it manually but it didn't seem worth the effort.

+        });
+      } catch (exception) {
+        print('Could not open log file: $exception');
+        exitCode = 1;
+        return;
+      }
+    }
     int port;
     bool serve_http = false;
     if (results[PORT_OPTION] != null) {
       serve_http = true;
       try {
         port = int.parse(results[PORT_OPTION]);
       } on FormatException {
         print('Invalid port number: ${results[PORT_OPTION]}');
         print('');
         _printUsage(parser);
@@ skipping 16 matching lines @@
   /**
    * Print information about how to use the server.
    */
   void _printUsage(ArgParser parser) {
     print('Usage: $BINARY_NAME [flags]');
     print('');
     print('Supported flags are:');
     print(parser.getUsage());
   }
 }