Mount TreeArtifact directories as inputs to Spawns.

Fixes https://github.com/bazelbuild/bazel/issues/1928.

--
PiperOrigin-RevId: 141077737
MOS_MIGRATED_REVID=141077737

1 files changed, 11 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/sandbox/SpawnHelpers.java b/src/main/java/com/google/devtools/build/lib/sandbox/SpawnHelpers.java
index 34ddd9e782..1bfa16b197 100644
--- a/src/main/java/com/google/devtools/build/lib/sandbox/SpawnHelpers.java
+++ b/src/main/java/com/google/devtools/build/lib/sandbox/SpawnHelpers.java
@@ -187,6 +187,17 @@ public final class SpawnHelpers {
       }
     }
 
+    // ActionInputHelper#expandArtifacts above expands empty TreeArtifacts into an empty list.
+    // However, actions that accept TreeArtifacts as inputs generally expect that the empty
+    // directory is created. So here we explicitly mount the directories of the TreeArtifacts as
+    // inputs.
+    for (ActionInput input : spawn.getInputFiles()) {
+      if (input instanceof Artifact && ((Artifact) input).isTreeArtifact()) {
+        PathFragment mount = new PathFragment(input.getExecPathString());
+        mounts.put(mount, execRoot.getRelative(mount));
+      }
+    }
+
     for (ActionInput input : inputs) {
       if (input.getExecPathString().contains("internal/_middlemen/")) {
         continue;