Dunk fails when Git config "diff.mnemonicPrefix" is enabled

[alexbarton]

When diff.mnemonicPrefix is enabled, dunk fails with errors like this:

❯ git config --global diff.mnemonicPrefix
true
❯ git diff | dunk
Traceback (most recent call last):
  File "/home/alex/.local/bin/dunk", line 10, in <module>
    sys.exit(main())
             ^^^^^^
  File "/home/alex/.local/share/uv/tools/dunk/lib/python3.12/site-packages/dunk/dunk.py", line 83, in main
    _run_dunk()
  File "/home/alex/.local/share/uv/tools/dunk/lib/python3.12/site-packages/dunk/dunk.py", line 132, in _run_dunk
    target_code = target_file.read_text()
                  ^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/alex/.local/share/uv/python/cpython-3.12.9-linux-x86_64-gnu/lib/python3.12/pathlib.py", line 1027, in read_text
    with self.open(mode='r', encoding=encoding, errors=errors) as f:
         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/alex/.local/share/uv/python/cpython-3.12.9-linux-x86_64-gnu/lib/python3.12/pathlib.py", line 1013, in open
    return io.open(self, mode, buffering, encoding, errors, newline)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '/home/Alex/WIP/Dunk/i/xyz/…'

Filename redacted, but basically it does not recognise the other prefixes than a/ and b/ in the git diff output:

diff --git i/.vim/spell/alex.utf-8.add w/.vim/spell/alex.utf-8.add
index 494d43d..55b615e 100644
--- i/xyz/…/file
+++ w/xyz/…/file

[SuperMeepEnby]

This is an issue with the library used to make PatchedFile objects : https://github.com/matiasb/python-unidiff/blob/master/unidiff/patch.py

They hardcode removal of a and b but forgot there are mnemonic letters such as i and w.

I'll try to push a patch to this lib when I can.

Edit: someone already did it https://github.com/matiasb/python-unidiff/pull/121/files
Edit2: I just learned about Github having messages to mention issues from a project in another one so it was just written above 😅

[alexbarton]

Thank you very mich, @SuperMeepBoy – and we'll see. But I'm not that optimistic, the last commit to matiasb/python-unidiff was almost 2 years ago … looks not like „super active development“ …

[SuperMeepEnby]

@alexbarton That's what I saw too… Maybe someone should fork it? I don't really know how it works. Or maybe the project should have a python-unidiff folder of their own in their source. I don't know what is the best practice.

Edit: I'm going to look at how to maintain this package when I have time.

[SuperMeepEnby]

So I pushed unidiff2 on PyPi. I am going to take a look in other things that need to be fixed/changed and release new versions of that library.

The unidiff2 integrates the work of danwald who suggested a patch for Git mnemonic prefixes. It should work if dunk uses the new package now.

[SuperMeepEnby]

My last unidiff2 was not working. I fixed it while I was adding a bunch of CI stuff.

Now it works. If you want to enjoy dunk with your mnemonicPrefixes you can :

1. uninstall dunk temporarily (the time @darrenburns notices this and uses unidiff2 instead of unidiff)
2. clone the project and move into it
3. edit pyproject.toml and replace unidiff with unidiff2
4. pipx install .

I'll make a PR if someone has not when I have time to move from unidiff to unidiff2.