[jira] [Created] (HADOOP-13191) FileSystem#listStatus should not return null

["John Zhuge (JIRA)" <ji...@apache.org>]

John Zhuge created HADOOP-13191:
-----------------------------------

             Summary: FileSystem#listStatus should not return null
                 Key: HADOOP-13191
                 URL: https://issues.apache.org/jira/browse/HADOOP-13191
             Project: Hadoop Common
          Issue Type: Bug
          Components: fs
    Affects Versions: 2.6.0
            Reporter: John Zhuge
            Assignee: John Zhuge
            Priority: Minor


This came out of discussion in HADOOP-12718. The {{FileSystem#listStatus}} contract does not indicate {{null}} is a valid return and some callers do not test {{null}} before use:

AbstractContractGetFileStatusTest#testListStatusEmptyDirectory:
{code}
    assertEquals("ls on an empty directory not of length 0", 0,
        fs.listStatus(subfolder).length);
{code}

ChecksumFileSystem#copyToLocalFile:
{code}
      FileStatus[] srcs = listStatus(src);
      for (FileStatus srcFile : srcs) {
{code}

SimpleCopyLIsting#getFileStatus:
{code}
      FileStatus[] fileStatuses = fileSystem.listStatus(path);
      if (excludeList != null && excludeList.size() > 0) {
        ArrayList<FileStatus> fileStatusList = new ArrayList<>();
        for(FileStatus status : fileStatuses) {
{code}

IMHO, there is no good reason for {{listStatus}} to return {{null}}. It should return empty list instead.

To enforce the contract that null is an invalid return, update javadoc and consider Intellij IDEA's @Nullable and @NotNull annotations.

So far, I am only aware of the following functions that can return null:
* RawLocalFileSystem#listStatus



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