HADOOP-13830. Intermittent failure of ITestS3NContractRootDir#testRecursiveRootListing: "Can not create a Path from an empty string". Contributed by Steve Loughran

(cherry picked from commit 3fd844b99fdfae6be6e5e261f371d175aad14229)

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3native/NativeS3FileSystem.java

@@ -574,7 +574,12 @@ public class NativeS3FileSystem extends FileSystem {
       for (String commonPrefix : listing.getCommonPrefixes()) {
         Path subpath = keyToPath(commonPrefix);
         String relativePath = pathUri.relativize(subpath.toUri()).getPath();
-        status.add(newDirectory(new Path(absolutePath, relativePath)));
+        // sometimes the common prefix includes the base dir (HADOOP-13830).
+        // avoid that problem by detecting it and keeping it out
+        // of the list
+        if (!relativePath.isEmpty()) {
+          status.add(newDirectory(new Path(absolutePath, relativePath)));
+        }
       }
       priorLastKey = listing.getPriorLastKey();
     } while (priorLastKey != null);