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https://issues.apache.org/jira/browse/HADOOP-13191?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15299346#comment-15299346
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John Zhuge edited comment on HADOOP-13191 at 5/25/16 2:44 AM:
--------------------------------------------------------------
Patch 001:
* Update {{listStatus}} doc in filesystem.md
* Annotate {{FileSystem#listStatus}} with @Nonnull (from javax.annotation
supported by IntelliJ)
* Restrict {{FileSystem#listStatus}} throw list to {{IOException}} since
{{FileNotFoundException}} is a subclass of {{IOException}}
* Add {{AccessControlException}} to {{FileSystem#listStatus}} javadoc
* Fix {{RawLocalFileSystem#listStatus}} to return empty list when
{{localf.list()}} returns null
* Fix {{listStatus}} in subclasses of {{FileSystem}} to return empty list
instead of null. Only found them in test classes.
* Parse 276 callers of {{FileSystem#listStatus}}:
** If it only handles {{FileNotFoundException}} but not {{IOException}}, fix
it. Only found 2 cases.
** If it does not have any catch clause, do nothing.
** If it checks null return and list length == 0, essentially no-op, do nothing.
Needs discussion:
* I am ok not to add @Nonnull annotations although it is nice to have.
* What to expect from {{listStatus(path)}} when the path is an accessible file?
was (Author: jzhuge):
Patch 001:
* Update {{listStatus}} doc in filesystem.md
* Annotate {{FileSystem#listStatus}} with @Nonnull
* Restrict {{FileSystem#listStatus}} throw list to {{IOException}} only since
{{FileNotFoundException}} is a subclass of {{IOException}}
* Add {{AccessControlException}} to {{FileSystem#listStatus}} javadoc
* Fix {{RawLocalFileSystem#listStatus}} to return empty list when
{{localf.list()}} returns null
* Fix {{listStatus}} in subclasses of {{FileSystem}} to return empty list
instead of null. Only found them in tests.
* Parse 276 callers of {{FileSystem#listStatus}}:
** If it only handles {{FileNotFoundException}} but not {{IOException}}, fix
it. Only found 2 cases.
** If it does not have any catch clause, do nothing.
** If it check null return and list length == 0, essentially no-op, do nothing.
Needs discussion:
* I am ok not to add @Nonnull annotations although it is nice to have.
* What to expect from {{listStatus(path)}} when the path is an accessible file?
> 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
>
>
> 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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