Allow SkyFunctions to return a sentinel value indicating that all of a node's in-progress data should be forgotten, and its evaluation should be restarted from scratch, as if it were freshly created/dirtied. To guard against this happening unexpectedly, any such events are passed to a GraphInconsistencyReceiver, which can verify that the SkyFunction is behaving properly.

This is the first change in a series to permit action rewinding when it is discovered that a previously generated input file is no longer available. When an action detects that one of its inputs is unusable, it can return this sentinel value, causing it to be re-evaluated from scratch. Follow-up changes will make the node corresponding to the input, and the node corresponding to the action that generated the input, dirty when this happens, causing the upstream action to be re-run, regenerating the desired input.

Currently works for builds that do not keep edges, although follow-ups may make this possible for all builds.

PiperOrigin-RevId: 194863097

1 files changed, 5 insertions, 1 deletions

diff --git a/src/main/java/com/google/devtools/build/skyframe/AbstractExceptionalParallelEvaluator.java b/src/main/java/com/google/devtools/build/skyframe/AbstractExceptionalParallelEvaluator.java
index 9526c855d9..e4a4193d57 100644
--- a/src/main/java/com/google/devtools/build/skyframe/AbstractExceptionalParallelEvaluator.java
+++ b/src/main/java/com/google/devtools/build/skyframe/AbstractExceptionalParallelEvaluator.java
@@ -86,7 +86,8 @@ public abstract class AbstractExceptionalParallelEvaluator<E extends Exception>
       ErrorInfoManager errorInfoManager,
       boolean keepGoing,
       int threadCount,
-      DirtyTrackingProgressReceiver progressReceiver) {
+      DirtyTrackingProgressReceiver progressReceiver,
+      GraphInconsistencyReceiver graphInconsistencyReceiver) {
     super(
         graph,
         graphVersion,
@@ -98,6 +99,7 @@ public abstract class AbstractExceptionalParallelEvaluator<E extends Exception>
         keepGoing,
         threadCount,
         progressReceiver,
+        graphInconsistencyReceiver,
         new SimpleCycleDetector());
   }
 
@@ -111,6 +113,7 @@ public abstract class AbstractExceptionalParallelEvaluator<E extends Exception>
       ErrorInfoManager errorInfoManager,
       boolean keepGoing,
       DirtyTrackingProgressReceiver progressReceiver,
+      GraphInconsistencyReceiver graphInconsistencyReceiver,
       ForkJoinPool forkJoinPool,
       CycleDetector cycleDetector) {
     super(
@@ -123,6 +126,7 @@ public abstract class AbstractExceptionalParallelEvaluator<E extends Exception>
         errorInfoManager,
         keepGoing,
         progressReceiver,
+        graphInconsistencyReceiver,
         forkJoinPool,
         cycleDetector);
   }