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, 2 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/packages/AbstractPackageLoader.java b/src/main/java/com/google/devtools/build/lib/skyframe/packages/AbstractPackageLoader.java
index 0c63193fea..d71830427d 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/packages/AbstractPackageLoader.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/packages/AbstractPackageLoader.java
@@ -76,6 +76,7 @@ import com.google.devtools.build.skyframe.Differencer;
 import com.google.devtools.build.skyframe.ErrorInfo;
 import com.google.devtools.build.skyframe.EvaluationProgressReceiver;
 import com.google.devtools.build.skyframe.EvaluationResult;
+import com.google.devtools.build.skyframe.GraphInconsistencyReceiver;
 import com.google.devtools.build.skyframe.ImmutableDiff;
 import com.google.devtools.build.skyframe.InMemoryMemoizingEvaluator;
 import com.google.devtools.build.skyframe.Injectable;
@@ -333,6 +334,7 @@ public abstract class AbstractPackageLoader implements PackageLoader {
             makeFreshSkyFunctions(),
             preinjectedDifferencer,
             new EvaluationProgressReceiver.NullEvaluationProgressReceiver(),
+            GraphInconsistencyReceiver.THROWING,
             new MemoizingEvaluator.EmittedEventState(),
             /*keepEdges=*/ false));
   }