[IO-692] PathUtils delete throws an exception when deleting a symlink that points to a file that does not exist

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.8.0
• Fix Version/s: 2.9.0

Environment

java version "1.8.0_202" Java(TM) SE Runtime Environment (build 1.8.0_202-b08) Java HotSpot(TM) 64-Bit Server VM (build 25.202-b08, mixed mode)

• Assignee: Unassigned
• Reporter: Matthew Rooney
• Created: 11/Nov/20 00:15
• Updated: 06/Dec/20 23:26
• Resolved: 06/Dec/20 23:26

Description

PathUtils.delete throws an Exception when deleting a symlink to a file that doesn't exist, in our case this was when the files were deleted out of sequence.

Minimal reproducing code running as a unit test (scala). This creates a symlink to a fail that does not exist at all.

val file = Files.createSymbolicLink(
  Paths.get("target", "x.txt"),
  Paths.get("target",  "y.txt").toAbsolutePath,
)
PathUtils.delete(file)

This throws the following exception

[error]    java.nio.file.NoSuchFileException: target/x.txt (UnixException.java:86)
[error] sun.nio.fs.UnixException.translateToIOException(UnixException.java:86)
[error] sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:102)
[error] sun.nio.fs.UnixException.rethrowAsIOException(UnixException.java:107)
[error] sun.nio.fs.UnixFileAttributeViews$Basic.readAttributes(UnixFileAttributeViews.java:55)
[error] sun.nio.fs.UnixFileSystemProvider.readAttributes(UnixFileSystemProvider.java:144)
[error] org.apache.commons.io.file.PathUtils.deleteFile(PathUtils.java:361)
[error] org.apache.commons.io.file.PathUtils.delete(PathUtils.java:304)
[error] org.apache.commons.io.file.PathUtils.delete(PathUtils.java:280)

The offending code is this in PathUtils

public static PathCounters deleteFile(final Path file, final DeleteOption... options) throws IOException {
    // Files.deleteIfExists() never follows links, so use LinkOption.NOFOLLOW_LINKS in other calls to Files.
    if (Files.isDirectory(file, LinkOption.NOFOLLOW_LINKS)) {
        throw new NoSuchFileException(file.toString());
    }
    final PathCounters pathCounts = Counters.longPathCounters();
    final boolean exists = Files.exists(file, LinkOption.NOFOLLOW_LINKS);
    final long size = exists ? Files.size(file) : 0;
    if (overrideReadOnly(options) && exists) {
        setReadOnly(file, false, LinkOption.NOFOLLOW_LINKS);
    }
    if (Files.deleteIfExists(file)) {
        pathCounts.getFileCounter().increment();
        pathCounts.getByteCounter().add(size);
    }
    return pathCounts;
}

This manifests because 

Files.exists(file, LinkOption.NOFOLLOW_LINKS); // this always returns true if the symlink exists

Files.size(file) // this throws an exception because there is no file to check the size of

A guess at the solution would be to only check the size if the file exists and is not a symlink

final long size = exists && !Files.isSymbolicLink() ? Files.size(file) : 0;

This was discovered when using FileUtils.deleteDirectory where we have a structure like the following. We clean up these directories when the process finishes, since upgrading to 2.8.0 this fails if the parent directory is deleted before the child.

 work_dir/
   parent_dir/
     big_file.txt
   child_dir/
     symlink_to_big_file.txt

As a work around using PathUtils.deleteDirectory seems to work regardless of the deletion order