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pkg/analyzer/lib/file_system/memory_file_system.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 memory_file_system;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/src/generated/engine.dart' show TimestampedData;
@@ skipping 29 matching lines @@
       new HashMap<String, _MemoryResource>();
   final Map<String, String> _pathToContent = new HashMap<String, String>();
   final Map<String, int> _pathToTimestamp = new HashMap<String, int>();
   final Map<String, List<StreamController<WatchEvent>>> _pathToWatchers =
       new HashMap<String, List<StreamController<WatchEvent>>>();
   int nextStamp = 0;
 
   @override
   Context get pathContext => posix;
 
+  /**
+   * Simulate revoked file access

[scheglov, 2015/02/22 19:31:31]

This comment describes the method from the perspective of one its applications.
It would be easier to understand if we explicitly stated that it will return a
snapshot and clear everything.

[danrubel, 2015/02/24 02:29:45]

Good point. I reworked this into a deleteFolder method with an appropriate
description.

+   * and return an object that can be passed to [restore].
+   */
+  clear() {

[scheglov, 2015/02/22 19:31:31]

Could we have some type here and in "restore"?
Even if we don't have any methods in the interface, just an empty marker
interface would be nicer than "dynamic" IMHO.

[danrubel, 2015/02/24 02:29:45]

That makes sense. Instead it was decided that a restore point did not make
sense, so I moved the restore point functionality out of this class and into the
test itself.

+    var restorePoint = new _MemoryRestorePoint(this);
+    _pathToResource.clear();
+    _pathToContent.clear();
+    _pathToTimestamp.clear();
+    // TODO(danrubel) notify watchers
+    return restorePoint;
+  }
+
+  /**
+   * Simulate restored file access based upon some earlier call to [clear].
+   */
+  void restore(var restorePoint) {
+    _pathToResource.clear();
+    _pathToContent.clear();
+    _pathToTimestamp.clear();
+    (restorePoint as _MemoryRestorePoint).restore(this);
+    // TODO(danrubel) notify watchers
+  }
+
   void deleteFile(String path) {
     _checkFileAtPath(path);
     _pathToResource.remove(path);
     _pathToContent.remove(path);
     _pathToTimestamp.remove(path);
     _notifyWatchers(path, ChangeType.REMOVE);
   }
 
   @override
   Resource getResource(String path) {
@@ skipping 82 matching lines @@
             {
           streamController.add(new WatchEvent(changeType, path));
         }
       }
     });
   }
 }
 
 
 /**
+ * A restore point captures the [MemoryResourceProvider] state
+ * so that it can be restored at later point.
+ */
+class _MemoryRestorePoint {
+  final Map<String, _MemoryResource> _pathToResource =
+      new HashMap<String, _MemoryResource>();
+  final Map<String, String> _pathToContent = new HashMap<String, String>();
+  final Map<String, int> _pathToTimestamp = new HashMap<String, int>();
+
+  _MemoryRestorePoint(MemoryResourceProvider provider) {
+    _pathToResource.addAll(provider._pathToResource);
+    _pathToContent.addAll(provider._pathToContent);
+    _pathToTimestamp.addAll(provider._pathToTimestamp);
+  }
+
+  void restore(MemoryResourceProvider provider) {
+    provider._pathToResource.addAll(_pathToResource);
+    provider._pathToContent.addAll(_pathToContent);
+    provider._pathToTimestamp.addAll(_pathToTimestamp);
+  }
+}
+
+
+/**
  * An in-memory implementation of [File] which acts like a symbolic link to a
  * non-existent file.
  */
 class _MemoryDummyLink extends _MemoryResource implements File {
   _MemoryDummyLink(MemoryResourceProvider provider, String path)
       : super(provider, path);
 
   @override
   bool get exists => false;
 
@@ skipping 214 matching lines @@
   bool operator ==(other) {
     if (runtimeType != other.runtimeType) {
       return false;
     }
     return path == other.path;
   }
 
   @override
   String toString() => path;
 }