Library Cycle invalidation

pkg/analyzer/lib/src/task/driver.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.driver;
 
 import 'dart:async';
 import 'dart:collection';
 
 import 'package:analyzer/src/context/cache.dart';
@@ skipping 455 matching lines @@
   CacheEntry getCacheEntry(AnalysisTarget target);
 }
 
 /**
  * An exception indicating that an attempt was made to perform a task on a
  * target while gathering the inputs to perform the same task for the same
  * target.
  */
 class InfiniteTaskLoopException extends AnalysisException {
   /**
+   * A concrete cyclic path of [TargetedResults] within the [dependencyCycle],
+   * `null` if no such path exists.  All nodes in the path are in the
+   * dependencyCycle, but the path is not guaranteed to cover the
+   * entire cycle.
+   */
+  final List<TargetedResult> cyclicPath;

[Leaf, 2015/10/19 22:32:27]

Not sure if this is the right way to surface this.  I wrote some debugging code
(see model.dart) that computes an actual concrete path through the
dependencyCycle, which I found made debugging the issue much simpler since there
are often a very large number of edges on each node in the cycle.  I thought it
would be worthwhile to keep that code around.  If preferred though, I can take
it out, or surface it in a different way.

[Brian Wilkerson, 2015/10/19 23:01:40]

If it makes debugging easier without hurting performance in the non-error case,
then it should stay in.

+
+  /**
    * If a dependency cycle was found while computing the inputs for the task,
    * the set of [WorkItem]s contained in the cycle (if there are overlapping
    * cycles, this is the set of all [WorkItem]s in the entire strongly
    * connected component).  Otherwise, `null`.
    */
   final List<WorkItem> dependencyCycle;
 
   /**
    * Initialize a newly created exception to represent a failed attempt to
    * perform the given [task] due to the given [dependencyCycle].
    */
-  InfiniteTaskLoopException(AnalysisTask task, this.dependencyCycle)
+  InfiniteTaskLoopException(AnalysisTask task, this.dependencyCycle,
+      [this.cyclicPath])
       : super(
             'Infinite loop while performing task ${task.descriptor.name} for ${task.target}');
 }
 
 /**
  * Object used by CycleAwareDependencyWalker to report a single strongly
  * connected component of nodes.
  */
 class StronglyConnectedComponent<Node> {
   /**
@@ skipping 261 matching lines @@
   final TaskManager taskManager;
 
   _WorkOrderDependencyWalker(this.taskManager, WorkItem startingNode)
       : super(startingNode);
 
   @override
   WorkItem getNextInput(WorkItem node, List<WorkItem> skipInputs) {
     return node.gatherInputs(taskManager, skipInputs);
   }
 }