ResourceNotFound - moving files on the same filesystem with preserve_time=True

[Marcel Johannesmann]

Hi,
while experimenting with the FS lib, I’ve encountered an unexpected ResourceNotFound error. The error is raised if the param preserve_time=True and we try to move a file on the same OS or in-memory filesystem.

This block represents a reproduceable example for a MemoryFS:

    mem_fs = memoryfs.MemoryFS()

    mem_fs.makedir("foo")
    mem_fs.writetext("foo/README.md", "Tetris clone")

    move_file(
        src_fs=mem_fs,
        src_path="foo/README.md",
        dst_fs=mem_fs,
        dst_path="foo/README_2.md",
        preserve_time=True,
    )

The raised error message:

./tests/test_resource_error.py::test_move_between_same_fs_mem Failed: [undefined]fs.errors.ResourceNotFound: resource 'foo/README.md' not found
def test_move_between_same_fs_mem():
        mem_fs = memoryfs.MemoryFS()
    
        mem_fs.makedir("foo")
        mem_fs.writetext("foo/README.md", "Tetris clone")
    
>       move_file(
            src_fs=mem_fs,
            src_path="foo/README.md",
            dst_fs=mem_fs,
            dst_path="foo/README_2.md",
            preserve_time=True,
        )

tests\test_resource_error.py:31: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
fs\move.py:68: in move_file
    _src_fs.move(
fs\memoryfs.py:478: in move
    copy_modified_time(self, src_path, self, dst_path)
fs\copy.py:532: in copy_modified_time
    src_meta = _src_fs.getinfo(src_path, namespaces)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _

self = MemoryFS(), path = 'foo/README.md', namespaces = ('details',)

    def getinfo(self, path, namespaces=None):
        # type: (Text, Optional[Collection[Text]]) -> Info
        _path = self.validatepath(path)
        dir_entry = self._get_dir_entry(_path)
        if dir_entry is None:
>           raise errors.ResourceNotFound(path)
E           fs.errors.ResourceNotFound: resource 'foo/README.md' not found

fs\memoryfs.py:394: ResourceNotFound

I have modified the test case test_move_file_same_fs and found similar errors for OS- and Temp-filesystems. For my understanding, the current implementation wants to copy the file’s metadata, after moving it or renaming its path. Therefore, the copy_modified_time function encounters a missing resource under these conditions:

• moving a file on the same filesystem
• preserve_time=True

AND either

1. copy_modified_time is called after moving the file, see memoryfs.py

2. or FS.move of base.py is used and the filesystem supports renaming, see base.py

Is this a limitation of my system (Win11 x64)?
I could not find similar issues or information in the docs.

If this is a not yet supported edge case, I would suggest that we read the file’s meta data first, then move it and update the meta info afterwards.

Any review and comments are welcome!
Regards

[Andrew Scheller]

Yup, it sounds like you've found a bug, and it sounds like you've already identified the fix. Good work.
Do you want to submit a suitable PR with the fix and updated tests?

[Marcel Johannesmann]

Gladly, I'm going to submit a draft tomorrow at the latest. Thanks for the feedback!