Detect concurrent edits.

dart/site/try/project_server.dart

 // Copyright (c) 2012, 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 trydart.projectServer;
 
 import 'dart:io';
 
+import 'dart:async' show
+    Future;
+
 import 'dart:convert' show
     HtmlEscape,
     JSON,
     UTF8;
 
 class WatchHandler {
   final WebSocket socket;
 
   final Set<String> watchedFiles;
 
   static final Set<WatchHandler> handlers = new Set<WatchHandler>();
 
   static const Map<int, String> fsEventNames = const <int, String>{
     FileSystemEvent.CREATE: 'create',
     FileSystemEvent.DELETE: 'delete',
     FileSystemEvent.MODIFY: 'modify',
     FileSystemEvent.MOVE: 'move',
   };
 
   WatchHandler(this.socket, Iterable<String> watchedFiles)
       : this.watchedFiles = watchedFiles.toSet();
 
   handleFileSystemEvent(FileSystemEvent event) {
-    String type = event.isDirectory ? 'directory' : 'file';
-    String eventType = fsEventNames[event.type];
-    if (eventType == null) eventType = 'unknown';
-    socket.add(JSON.encode({eventType: [event.path]}));
+    if (event.isDirectory) return;
+    String type = fsEventNames[event.type];
+    if (type == null) type = 'unknown';
+    String path = new Uri.file(event.path).pathSegments.last;
+    shouldIgnore(type, path).then((bool ignored) {
+      if (ignored) return;
+      socket.add(JSON.encode({type: [path]}));
+    });
+  }
+
+  Future<bool> shouldIgnore(String type, String path) {
+    switch (type) {
+      case 'create':
+        return new Future<bool>.value(!watchedFiles.contains(path));
+      case 'delete':
+        return Conversation.listProjectFiles().then((List<String> files) {
+          watchedFiles
+              ..retainAll(files)
+              ..addAll(files);
+          return watchedFiles.contains(path);
+        });
+      case 'modify':
+        return new Future<bool>.value(false);
+      default:
+        print('Unhandled fs-event for $path ($type).');
+        return new Future<bool>.value(true);
+    }
   }
 
   onData(_) {
     // TODO(ahe): Move POST code here?
   }
 
   onDone() {
     handlers.remove(this);
   }
 
@@ skipping 379 matching lines @@
     Conversation.packageRoot = Uri.base.resolve(arguments[4]);
   }
   HttpServer.bind(host, port).then((HttpServer server) {
     print('HTTP server started on http://$host:${server.port}/');
     server.listen(Conversation.onRequest, onError: Conversation.onError);
   }).catchError((e) {
     print("HttpServer.bind error: $e");
     exit(1);
   });
 }