1 files changed, 6 insertions, 21 deletions
diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/ActionExecutionFunction.java b/src/main/java/com/google/devtools/build/lib/skyframe/ActionExecutionFunction.java
index aaa9221098..4e61f8c6bd 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/ActionExecutionFunction.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/ActionExecutionFunction.java
@@ -435,8 +435,12 @@ public class ActionExecutionFunction implements SkyFunction, CompletionReceiver
           state.discoveredInputs =
               skyframeActionExecutor.discoverInputs(
                   action, metadataHandler, env, state.actionFileSystem);
-          Preconditions.checkState(state.discoveredInputs != null,
-              "discoverInputs() returned null on action %s", action);
+          Preconditions.checkState(
+              env.valuesMissing() == (state.discoveredInputs == null),
+              "discoverInputs() must return null iff requesting more dependencies.");
+          if (state.discoveredInputs == null) {
+            return null;
+          }
         } catch (MissingDepException e) {
           Preconditions.checkState(env.valuesMissing(), action);
           return null;
@@ -448,24 +452,6 @@ public class ActionExecutionFunction implements SkyFunction, CompletionReceiver
         return null;
       }
 
-      // Stage 1 finished, let's do stage 2. The stage 1 of input discovery will have added some
-      // files with addDiscoveredInputs() and then have waited for those files to be available
-      // by returning null if env.valuesMissing() returned true. So stage 2 can now access those
-      // inputs to discover even more inputs and then potentially also wait for those to be
-      // available.
-      if (state.discoveredInputsStage2 == null) {
-        state.discoveredInputsStage2 = action.discoverInputsStage2(env);
-        if (env.valuesMissing()) {
-          return null;
-        }
-      }
-      if (state.discoveredInputsStage2 != null) {
-        addDiscoveredInputs(
-            state.inputArtifactData, state.expandedArtifacts, state.discoveredInputsStage2, env);
-        if (env.valuesMissing()) {
-          return null;
-        }
-      }
       metadataHandler =
           new ActionMetadataHandler(
               state.inputArtifactData,
@@ -821,7 +807,6 @@ public class ActionExecutionFunction implements SkyFunction, CompletionReceiver
     Map<Artifact, Collection<Artifact>> expandedArtifacts = null;
     Token token = null;
     Iterable<Artifact> discoveredInputs = null;
-    Iterable<Artifact> discoveredInputsStage2 = null;
     ActionExecutionValue value = null;
     FileSystem actionFileSystem = null;