Work in progress: front end hot reload API

pkg/front_end/lib/src/base/source.dart

 // Copyright (c) 2016, 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.
 
 import 'package:front_end/src/base/analysis_target.dart';
 import 'package:front_end/src/base/timestamped_data.dart';
 import 'package:front_end/src/base/uri_kind.dart';
+import 'package:path/path.dart' as pathos;
+
+/// Base class providing implementations for the methods in [Source] that don't
+/// require filesystem access.
+abstract class BasicSource extends Source {
+  final Uri uri;
+
+  BasicSource(this.uri);
+
+  @override
+  String get encoding => uri.toString();
+
+  @override
+  String get fullName => encoding;
+
+  @override
+  int get hashCode => uri.hashCode;
+
+  @override
+  bool get isInSystemLibrary => uri.scheme == 'dart';
+
+  @override
+  String get shortName => pathos.basename(fullName);
+
+  @override
+  bool operator ==(Object object) => object is Source && object.uri == uri;
+}
 
 /**
  * The interface `Source` defines the behavior of objects representing source code that can be
  * analyzed by the analysis engine.
  *
  * Implementations of this interface need to be aware of some assumptions made by the analysis
  * engine concerning sources:
  * * Sources are not required to be unique. That is, there can be multiple instances representing
  * the same source.
  * * Sources are long lived. That is, the engine is allowed to hold on to a source for an extended
@@ skipping 121 matching lines @@
    * Return `true` if this source exists.
    *
    * Clients should consider using the method [AnalysisContext.exists] because
    * contexts can have local overrides of the content of a source that the source is not aware of
    * and a source with local content is considered to exist even if there is no file on disk.
    *
    * @return `true` if this source exists
    */
   bool exists();
 }