Add File.modificationStamp accessor.

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;
 import 'package:analyzer/src/generated/source_io.dart';
 import 'package:path/path.dart';
 import 'package:watcher/watcher.dart';
 
 import 'file_system.dart';
 
 
 /**
- * Exception thrown when a memory [Resource] file operation fails.
- */
-class MemoryResourceException {
-  final path;
-  final message;
-
-  MemoryResourceException(this.path, this.message);
-
-  @override
-  String toString() {
-    return "MemoryResourceException(path=$path; message=$message)";
-  }
-}
-
-
-/**
  * An in-memory implementation of [ResourceProvider].
  * Use `/` as a path separator.
  */
 class MemoryResourceProvider implements ResourceProvider {
   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>();
   final Map<String, List<StreamController<WatchEvent>>> _pathToWatchers =
       new HashMap<String, List<StreamController<WatchEvent>>>();
@@ skipping 107 matching lines @@
  * 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;
 
-  String get _content {
-    throw new MemoryResourceException(path, "File '$path' could not be read");
+  int get modificationStamp {
+    int stamp = _provider._pathToTimestamp[path];
+    if (stamp == null) {
+      return -1;

[Brian Wilkerson, 2015/02/23 17:29:53]

Should this throw an exception? Is there an OS that allows negative modification
stamp values?

+    }
+    return stamp;
   }
 
-  int get _timestamp => _provider._pathToTimestamp[path];
+  String get _content {
+    throw new FileSystemException(path, 'File could not be read');
+  }
 
   @override
   Source createSource([Uri uri]) {
-    throw new MemoryResourceException(path, "File '$path' could not be read");
+    throw new FileSystemException(path, 'File could not be read');
   }
 
   @override
   bool isOrContains(String path) {
     return path == this.path;
   }
 }
 
 
 /**
  * An in-memory implementation of [File].
  */
 class _MemoryFile extends _MemoryResource implements File {
   _MemoryFile(MemoryResourceProvider provider, String path)
       : super(provider, path);
 
+  int get modificationStamp {
+    int stamp = _provider._pathToTimestamp[path];
+    if (stamp == null) {
+      throw new FileSystemException(path, 'File does not exist.');
+    }
+    return stamp;
+  }
+
   String get _content {
     String content = _provider._pathToContent[path];
     if (content == null) {
-      throw new MemoryResourceException(path, "File '$path' does not exist");
+      throw new FileSystemException(path, "File does not exist");
     }
     return content;
   }
 
-  int get _timestamp => _provider._pathToTimestamp[path];
-
   @override
   Source createSource([Uri uri]) {
     if (uri == null) {
       uri = posix.toUri(path);
     }
     return new _MemoryFileSource(this, uri);
   }
 
   @override
   bool isOrContains(String path) {
@@ skipping 25 matching lines @@
   @override
   String get fullName => _file.path;
 
   @override
   int get hashCode => _file.hashCode;
 
   @override
   bool get isInSystemLibrary => uriKind == UriKind.DART_URI;
 
   @override
-  int get modificationStamp => _file._timestamp;
+  int get modificationStamp {
+    try {
+      return _file.modificationStamp;
+    } on FileSystemException catch (e) {

[Brian Wilkerson, 2015/02/23 17:29:53]

Why is this exception is being caught?

+      return -1;
+    }
+  }
 
   @override
   String get shortName => _file.shortName;
 
   @override
   UriKind get uriKind {
     String scheme = uri.scheme;
     if (scheme == PackageUriResolver.PACKAGE_SCHEME) {
       return UriKind.PACKAGE_URI;
     } else if (scheme == DartUriResolver.DART_SCHEME) {
@@ skipping 123 matching lines @@
   bool operator ==(other) {
     if (runtimeType != other.runtimeType) {
       return false;
     }
     return path == other.path;
   }
 
   @override
   String toString() => path;
 }