Treat add events for known files as modifications instead of discarding them on Mac OS. Fixes pub s…

lib/src/directory_watcher/mac_os.dart

 // Copyright (c) 2013, 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 watcher.directory_watcher.mac_os;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as p;
@@ skipping 161 matching lines @@
       if (MacOSDirectoryWatcher.logDebugInfo) {
         print("[$_id] canonical event for $relativePath: "
             "${_formatEvent(canonicalEvent)}");
         print("[$_id] actionable events for $relativePath: "
             "${events.map(_formatEvent)}");
       }
 
       for (var event in events) {
         if (event is FileSystemCreateEvent) {
           if (!event.isDirectory) {
-            // Don't emit ADD events for files or directories that we already
-            // know about. Such an event comes from FSEvents reporting an add
-            // that happened prior to the watch beginning.
-            if (_files.contains(path)) continue;
+            // If we already know about the file, treat it like a modification.

[nweiz, 2015/01/22 00:20:19]

"treat it" -> "treat an ADD event"

+            // This can happen if a file is copied on top of an existing one.
+            // We'll see an ADD event for the latter file when from the user's
+            // perspective, the file's contents just changed.
+            var type = _files.contains(path)
+                ? ChangeType.MODIFY
+                : ChangeType.ADD;
 
-            _emitEvent(ChangeType.ADD, path);
+            _emitEvent(type, path);
             _files.add(path);
             continue;
           }
 
           if (_files.containsDir(path)) continue;
 
           var stream = Chain.track(new Directory(path).list(recursive: true));
           _listSubscription = stream.listen((entity) {
             if (entity is Directory) return;
             if (_files.contains(path)) return;
@@ skipping 290 matching lines @@
     } else if (event is FileSystemDeleteEvent) {
       return "delete $type $path";
     } else if (event is FileSystemModifyEvent) {
       return "modify $type $path";
     } else if (event is FileSystemMoveEvent) {
       return "move $type $path to "
           "${p.relative(event.destination, from: directory)}";
     }
   }
 }