Tighten invariants around dirtiness checking. We should never need to…

… create a child that's being checked by a parent (that was a legacy of when we delegated to enqueueChild), and such a child that is being checked should always be dirty or done, never fresh.

--
PiperOrigin-RevId: 149136909
MOS_MIGRATED_REVID=149136909

src/main/java/com/google/devtools/build/skyframe/ParallelEvaluator.java

@@ -262,8 +262,9 @@ private DirtyOutcome maybeHandleDirtyNode(NodeEntry state) throws InterruptedExc
             // usual, but we can't, because then the ErrorTransienceValue would remain as a dep,
             // which would be incorrect if, for instance, the value re-evaluated to a non-error.
             state.forceRebuild();
-            graph.get(
-                skyKey, Reason.RDEP_REMOVAL, ErrorTransienceValue.KEY).removeReverseDep(skyKey);
+            graph
+                .get(skyKey, Reason.RDEP_REMOVAL, ErrorTransienceValue.KEY)
+                .removeReverseDep(skyKey);
             return DirtyOutcome.NEEDS_EVALUATION;
           }
           if (!evaluatorContext.keepGoing()) {
@@ -307,14 +308,20 @@ private DirtyOutcome maybeHandleDirtyNode(NodeEntry state) throws InterruptedExc
           // always the last dep).
           state.addTemporaryDirectDepsGroupToDirtyEntry(directDepsToCheck);
 
-          // TODO(bazel-team): If this signals the current node, consider falling through to the
-          // VERIFIED_CLEAN case below directly, without scheduling a new Evaluate().
-          for (Map.Entry<SkyKey, ? extends NodeEntry> e :
-              graph
-                  .createIfAbsentBatch(skyKey, Reason.ENQUEUING_CHILD, directDepsToCheck)
-                  .entrySet()) {
+          Map<SkyKey, ? extends NodeEntry> oldChildren =
+              graph.getBatch(skyKey, Reason.ENQUEUING_CHILD, directDepsToCheck);
+          Preconditions.checkState(
+              oldChildren.size() == directDepsToCheck.size(),
+              "Not all old children were present: %s %s %s %s",
+              skyKey,
+              state,
+              directDepsToCheck,
+              oldChildren);
+          for (Map.Entry<SkyKey, ? extends NodeEntry> e : oldChildren.entrySet()) {
             SkyKey directDep = e.getKey();
             NodeEntry directDepEntry = e.getValue();
+            // TODO(bazel-team): If this signals the current node, consider falling through to the
+            // VERIFIED_CLEAN case below directly, without scheduling a new Evaluate().
             enqueueChild(skyKey, state, directDep, directDepEntry, /*depAlreadyExists=*/ true);
           }
           return DirtyOutcome.ALREADY_PROCESSED;