Remove test skip on Windows, fix the implementation.

Author: davidmorgan

pkgs/watcher/CHANGELOG.md

@@ -4,6 +4,9 @@
   the file was created immediately before the watcher was created. Now, if the
   file exists when the watcher is created then this modify event is not sent.
   This matches the Linux native and polling (Windows) watchers.
+- Bug fix: fix a spurious modify event with `DirectoryWatcher` on Windows that
+  was reported when a directory was renamed then a file was immediately renamed
+  to the old name of the directory.
 
 ## 1.1.4
 

pkgs/watcher/lib/src/directory_watcher/windows.dart

@@ -266,12 +266,16 @@ class _WindowsDirectoryWatcher
 
     for (var event in batch) {
       if (event is FileSystemMoveEvent) {
+        addEvent(
+            event.path, FileSystemDeleteEvent(event.path, event.isDirectory));
         var destination = event.destination;
         if (destination != null) {
-          addEvent(destination, event);
+          addEvent(destination,
+              FileSystemCreateEvent(event.path, event.isDirectory));
         }
+      } else {
+        addEvent(event.path, event);
       }
-      addEvent(event.path, event);
     }
 
     return eventsForPaths;
@@ -280,6 +284,9 @@ class _WindowsDirectoryWatcher
   /// Returns the canonical event from a batch of events on the same path, if
   /// one exists.
   ///
+  /// The batch must be an output of [_sortEvents] which guarantees it contains
+  /// no [FileSystemMoveEvent]s.
+  ///
   /// If [batch] doesn't contain any contradictory events (e.g. DELETE and
   /// CREATE, or events with different values for `isDirectory`), this returns a
   /// single event that describes what happened to the path in question.
@@ -306,9 +313,7 @@ class _WindowsDirectoryWatcher
       // (respectively) that will be contradictory.
       if (event is FileSystemModifyEvent) continue;
       assert(
-        event is FileSystemCreateEvent ||
-            event is FileSystemDeleteEvent ||
-            event is FileSystemMoveEvent,
+        event is FileSystemCreateEvent || event is FileSystemDeleteEvent,
       );
 
       // If we previously thought this was a MODIFY, we now consider it to be a
@@ -320,9 +325,7 @@ class _WindowsDirectoryWatcher
 
       // A CREATE event contradicts a REMOVE event and vice versa.
       assert(
-        type == FileSystemEvent.create ||
-            type == FileSystemEvent.delete ||
-            type == FileSystemEvent.move,
+        type == FileSystemEvent.create || type == FileSystemEvent.delete,
       );
       if (type != event.type) return null;
     }
@@ -334,8 +337,6 @@ class _WindowsDirectoryWatcher
         return FileSystemDeleteEvent(batch.first.path, isDir);
       case FileSystemEvent.modify:
         return FileSystemModifyEvent(batch.first.path, isDir, false);
-      case FileSystemEvent.move:
-        return null;
       default:
         throw StateError('unreachable');
     }

pkgs/watcher/test/directory_watcher/shared.dart

@@ -280,8 +280,6 @@ void sharedTests() {
         isRemoveEvent('old'),
         isAddEvent('new')
       ]);
-    }, onPlatform: {
-      'windows': const Skip('https://github.com/dart-lang/watcher/issues/21')
     });
 
     test('emits events for many nested files added at once', () async {