Fix bug(s) with Skylark import cycles: we assumed that a package that failed to load must have failed because of an exception, which is false in the case of cycles;

--
MOS_MIGRATED_REVID=135742248

1 files changed, 5 insertions, 2 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/skyframe/GraphBackedRecursivePackageProvider.java b/src/main/java/com/google/devtools/build/lib/skyframe/GraphBackedRecursivePackageProvider.java
index 5499189c9b..5e31b91832 100644
--- a/src/main/java/com/google/devtools/build/lib/skyframe/GraphBackedRecursivePackageProvider.java
+++ b/src/main/java/com/google/devtools/build/lib/skyframe/GraphBackedRecursivePackageProvider.java
@@ -85,8 +85,11 @@ public final class GraphBackedRecursivePackageProvider implements RecursivePacka
     if (graph.exists(pkgKey)) {
       pkgValue = (PackageValue) graph.getValue(pkgKey);
       if (pkgValue == null) {
-        throw (NoSuchPackageException)
-            Preconditions.checkNotNull(graph.getException(pkgKey), pkgKey);
+        NoSuchPackageException nspe = (NoSuchPackageException) graph.getException(pkgKey);
+        if (nspe != null) {
+          throw nspe;
+        }
+        throw new NoSuchPackageException(packageName, "Package depends on a cycle");
       }
     } else {
       // If the package key does not exist in the graph, then it must not correspond to any package,