Issue 26629. Detect cache inconsistency in GetContentTask.

pkg/analyzer/lib/src/task/general.dart

 // Copyright (c) 2015, 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 analyzer.src.task.general;
 
+import 'package:analyzer/src/context/cache.dart';
 import 'package:analyzer/src/generated/engine.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/task/general.dart';
 import 'package:analyzer/task/model.dart';
 
 /**
  * A task that gets the contents of the source associated with an analysis
  * target.
  */
 class GetContentTask extends SourceBasedAnalysisTask {
   /**
    * The task descriptor describing this kind of task.
    */
   static final TaskDescriptor DESCRIPTOR = new TaskDescriptor('GetContentTask',
       createTask, buildInputs, <ResultDescriptor>[CONTENT, MODIFICATION_TIME]);
 
   /**
    * Initialize a newly created task to access the content of the source
    * associated with the given [target] in the given [context].
    */
   GetContentTask(AnalysisContext context, AnalysisTarget target)
       : super(context, target);
 
   @override
   TaskDescriptor get descriptor => DESCRIPTOR;
 
   @override
   internalPerform() {
     Source source = getRequiredSource();
+    String content;
+    int modificationTime;
     try {
       TimestampedData<String> data = context.getContents(source);
-      outputs[CONTENT] = data.data;
-      outputs[MODIFICATION_TIME] = data.modificationTime;
+      content = data.data;
+      modificationTime = data.modificationTime;
     } catch (exception) {
-      outputs[CONTENT] = '';
-      outputs[MODIFICATION_TIME] = -1;
+      content = '';
+      modificationTime = -1;
+    }
+    outputs[CONTENT] = content;
+    outputs[MODIFICATION_TIME] = modificationTime;
+    _validateModificationTimeConsistency(modificationTime);
+  }
+
+  /**
+   * Validate that the [target] cache entry has the same modification time
+   * as the given.  Otherwise throw a new [ModificationTimeMismatchError] and
+   * instruct to invalidate targets content.
+   */
+  void _validateModificationTimeConsistency(int modificationTime) {
+    AnalysisContext context = this.context;
+    if (context is InternalAnalysisContext) {
+      CacheEntry entry = context.getCacheEntry(target);
+      if (entry != null && entry.modificationTime != modificationTime) {
+        entry.modificationTime = modificationTime;
+        entry.setState(CONTENT, CacheState.INVALID);
+        entry.setState(MODIFICATION_TIME, CacheState.INVALID);
+        throw new ModificationTimeMismatchError(target);
+      }
     }
   }
 
   /**
    * Return a map from the names of the inputs of this kind of task to the task
    * input descriptors describing those inputs for a task with the given [target].
    */
   static Map<String, TaskInput> buildInputs(AnalysisTarget target) {
     return <String, TaskInput>{};
   }
@@ skipping 19 matching lines @@
   SourceBasedAnalysisTask(AnalysisContext context, AnalysisTarget target)
       : super(context, target);
 
   @override
   String get description {
     Source source = target.source;
     String sourceName = source == null ? '<unknown source>' : source.fullName;
     return '${descriptor.name} for source $sourceName';
   }
 }