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https://issues.apache.org/jira/browse/HADOOP-13191?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15440217#comment-15440217
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Xiao Chen commented on HADOOP-13191:
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Thanks for working on this [~jzhuge].
Some review comments from me:
- This duplicates HADOOP-7352, which predates this jira. Maybe we can move the
patch and further discussions to there? The code changes are mostly in common
too.
- bq. (Steve L): I'm in favour of this, and returning an empty list.
IMHO returning an empty list is less surprising, throwing an IOE will make the
error more explicit. Although this jira maybe incompatible, I think returning
an empty list maintains a more compatible behavior (Client code may not need
any change if empty list), so personally inclined with empty list too.
- I don't think throwing {{AccessControlException}} in
{{RawLocalFileSystem#listStatus}} is correct. The javadoc of {{File#list}}
mentions various of scenarios, {{AccessControlException}} is one of those
scenarios. I think we could do sth similar to
[FileUtil|https://github.com/apache/hadoop/blob/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileUtil.java#L1147].
- Also I don't see much value in the comment before throwing. One can just
check javadoc to see what a method returns.
- Not sure about {{@Nonnull}}. Would this add a dependency to javax to common?
It's currently in hdfs only. I wouldn't worry about this normally, but would
like other people's thoughts since this is {{FileSystem.java}}.
> 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
> Attachments: HADOOP-13191.001.patch, HADOOP-13191.002.patch,
> HADOOP-13191.003.patch, HADOOP-13191.004.patch
>
>
> 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 throw IOExceptions upon errors or return empty list.
> To enforce the contract that null is an invalid return, update javadoc and
> leverage @Nullable/@NotNull/@Nonnull annotations.
> So far, I am only aware of the following functions that can return null:
> * RawLocalFileSystem#listStatus
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