HADOOP-13188 S3A file-create should throw error rather than overwrite directories. Contributed by Steve Loughran

hadoop-tools/hadoop-aws/src/main/java/org/apache/hadoop/fs/s3a/S3AFileSystem.java

@@ -598,9 +598,24 @@ public class S3AFileSystem extends FileSystem {
       boolean overwrite, int bufferSize, short replication, long blockSize,
       Progressable progress) throws IOException {
     String key = pathToKey(f);
+    S3AFileStatus status = null;
+    try {
+      // get the status or throw an FNFE
+      status = getFileStatus(f);
+
+      // if the thread reaches here, there is something at the path
+      if (status.isDirectory()) {
+        // path references a directory: automatic error
+        throw new FileAlreadyExistsException(f + " is a directory");
+      }
+      if (!overwrite) {
+        // path references a file and overwrite is disabled
+        throw new FileAlreadyExistsException(f + " already exists");
+      }
+      LOG.debug("Overwriting file {}", f);
+    } catch (FileNotFoundException e) {
+      // this means the file is not found
 
-    if (!overwrite && exists(f)) {
-      throw new FileAlreadyExistsException(f + " already exists");
     }
     instrumentation.fileCreated();
     if (getConf().getBoolean(FAST_UPLOAD, DEFAULT_FAST_UPLOAD)) {

hadoop-tools/hadoop-aws/src/test/java/org/apache/hadoop/fs/contract/s3a/TestS3AContractCreate.java

@@ -30,9 +30,4 @@ public class TestS3AContractCreate extends AbstractContractCreateTest {
     return new S3AContract(conf);
   }
 
-  @Override
-  public void testOverwriteEmptyDirectory() throws Throwable {
-    ContractTestUtils.skip(
-        "blobstores can't distinguish empty directories from files");
-  }
 }