Use EmptyActionInput instead of null in SpawnInputExpander

This simplifies some spawn runners, which no longer have to specially handle
null; unfortunately, the sandbox runners do not support VirtualActionInput,
so they still have to special-case it.

PiperOrigin-RevId: 181175408

1 files changed, 6 insertions, 2 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/exec/SpawnInputExpander.java b/src/main/java/com/google/devtools/build/lib/exec/SpawnInputExpander.java
index f30209df53..f9abca0137 100644
--- a/src/main/java/com/google/devtools/build/lib/exec/SpawnInputExpander.java
+++ b/src/main/java/com/google/devtools/build/lib/exec/SpawnInputExpander.java
@@ -24,6 +24,8 @@ import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.Artifact.ArtifactExpander;
 import com.google.devtools.build.lib.actions.RunfilesSupplier;
 import com.google.devtools.build.lib.actions.Spawn;
+import com.google.devtools.build.lib.actions.cache.VirtualActionInput;
+import com.google.devtools.build.lib.actions.cache.VirtualActionInput.EmptyActionInput;
 import com.google.devtools.build.lib.rules.fileset.FilesetActionContext;
 import com.google.devtools.build.lib.vfs.PathFragment;
 import java.io.IOException;
@@ -39,7 +41,8 @@ import java.util.TreeMap;
  * laid out.
  */
 public class SpawnInputExpander {
-  public static final ActionInput EMPTY_FILE = null;
+  @VisibleForTesting
+  static final ActionInput EMPTY_FILE = new EmptyActionInput("/dev/null");
 
   private final boolean strict;
 
@@ -129,7 +132,8 @@ public class SpawnInputExpander {
 
   /**
    * Convert the inputs of the given spawn to a map from exec-root relative paths to action inputs.
-   * In some cases, this generates empty files, for which it uses {@code null}.
+   * The returned map never contains {@code null} values; it uses {@link #EMPTY_FILE} for empty
+   * files, which is an instance of {@link VirtualActionInput}.
    */
   public SortedMap<PathFragment, ActionInput> getInputMapping(
       Spawn spawn, ArtifactExpander artifactExpander, ActionInputFileCache actionInputFileCache,