Fix crash when trying to obtain an FilesetOutputTree input in `Acti…

…onExecutionFunction`, where the owning analysis node for the Fileset is in the frontier.

PiperOrigin-RevId: 718223413
Change-Id: I7bd1bd0dd3727262e8a144343f4b1e7142e48827

src/main/java/com/google/devtools/build/lib/skyframe/ActionInputMapHelper.java

@@ -144,9 +144,26 @@ private static FilesetOutputTree getFilesetOutput(Environment env, SpecialArtifa
     ActionLookupData generatingActionKey = actionInput.getGeneratingActionKey();
     ActionLookupKey filesetActionLookupKey = generatingActionKey.getActionLookupKey();
 
-    ActionLookupValue filesetActionLookupValue =
-        (ActionLookupValue) env.getValue(filesetActionLookupKey);
+    SkyValue maybeActionLookupValue = env.getValue(filesetActionLookupKey);
 
+    // With Frontier-based Skycache, the SkyValue for the fileset analysis object may be a
+    // RemoteConfiguredTargetValue if it's not in the active set, and the remote fileset CT value
+    // doesn't contain actions for lookup. That is OK because we're only interested in the fileset
+    // output, which is not stored in the actions, but in the (potentially Skycache-cached)
+    // ActionExecutionValue.
+    //
+    // Additionally, `if (generatingAction instanceof SymlinkAction)` block below is also only
+    // triggered when building fileset symlinks, which is disabled in a Skycache build.
+    //
+    // So, for a Skycache build, we can skip the transitive action lookups below and obtain the
+    // FilesetOutputTree directory from the Fileset ActionExecutionValue immediately (which should
+    // be a Skycache cache hit anyway).
+    if (maybeActionLookupValue instanceof RemoteConfiguredTargetValue) {
+      return getFilesetOutputFromKey(generatingActionKey, env);
+    }
+
+    // Non-Skycache builds from here.
+    ActionLookupValue filesetActionLookupValue = (ActionLookupValue) maybeActionLookupValue;
     ActionAnalysisMetadata generatingAction =
         filesetActionLookupValue.getAction(generatingActionKey.getActionIndex());
     ActionLookupData filesetActionKey;
@@ -179,13 +196,19 @@ private static FilesetOutputTree getFilesetOutput(Environment env, SpecialArtifa
       filesetActionKey = generatingActionKey;
     }
 
-    // TODO(janakr: properly handle exceptions coming from here, or prove they can never happen in
-    //  practice.
+    return getFilesetOutputFromKey(filesetActionKey, env);
+  }
+
+  private static FilesetOutputTree getFilesetOutputFromKey(
+      ActionLookupData filesetActionKey, Environment env) throws InterruptedException {
+    // TODO: properly handle exceptions coming from here, or prove they can never happen in
+    // practice.
     ActionExecutionValue filesetValue = (ActionExecutionValue) env.getValue(filesetActionKey);
     if (filesetValue == null) {
       // At this point skyframe does not guarantee that the filesetValue will be ready, since
       // the current action does not directly depend on the outputs of the
-      // SkyframeFilesetManifestAction whose ActionExecutionValue (filesetValue) is needed here.
+      // SkyframeFilesetManifestAction whose ActionExecutionValue
+      // (com.google.devtools.build.lib.skyframe.Fileset) is needed here.
       return null;
     }
     return filesetValue.getFilesetOutput();

src/main/java/com/google/devtools/build/lib/skyframe/BUILD

@@ -509,6 +509,7 @@ java_library(
     deps = [
         ":action_execution_value",
         ":metadata_consumer_for_metrics",
+        ":rule_configured_target_value",
         ":tree_artifact_value",
         "//src/main/java/com/google/devtools/build/lib/actions",
         "//src/main/java/com/google/devtools/build/lib/actions:action_lookup_data",