Adding checks for empty metadata and digest.

This will avoid the uninformative NullPointerException for this case (#3913). The underlying cause is data dependency on directories, which we want to disable. In the future, it will be allowed, but in a more explicit form (e.g. trailing slash).

TESTED=no
RELNOTES: None
PiperOrigin-RevId: 176109375

1 files changed, 6 insertions, 0 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/remote/Digests.java b/src/main/java/com/google/devtools/build/lib/remote/Digests.java
index eadcb4c57e..c3b6e0d3a6 100644
--- a/src/main/java/com/google/devtools/build/lib/remote/Digests.java
+++ b/src/main/java/com/google/devtools/build/lib/remote/Digests.java
@@ -16,6 +16,7 @@ package com.google.devtools.build.lib.remote;
 
 import static java.nio.charset.StandardCharsets.UTF_8;
 
+import com.google.common.base.Preconditions;
 import com.google.common.hash.HashCode;
 import com.google.devtools.build.lib.actions.ActionInput;
 import com.google.devtools.build.lib.actions.MetadataProvider;
@@ -105,6 +106,11 @@ public final class Digests {
   public static Digest getDigestFromInputCache(ActionInput input, MetadataProvider cache)
       throws IOException {
     Metadata metadata = cache.getMetadata(input);
+    Preconditions.checkNotNull(metadata, "Input cache %s returned no value for %s", cache, input);
+    Preconditions.checkNotNull(
+        metadata.getDigest(),
+        "Null digest for %s, possible directory. Data dependencies on directories are not allowed.",
+        input);
     return buildDigest(metadata.getDigest(), metadata.getSize());
   }
 }