This has a merge conflict now.

Also, unfortunately most of us maintainers don't know much about vimscript and we'll need some help to review this. Can you explain what @% means?

Rebasing this should be trivial; the function that's being patched has just moved from plugin/black.vim to autoload/black.vim, but the relevant code is the same.

@x as an expression in vimscript evaluates to the contents of the x register. The % register stores the name of the current file, so @% is the name of the current file (which may be an empty string, if the current buffer is not associated with a file).

But... OK, both the existing code and the proposed code are broken. The vim.eval() call (whether it's vim.eval("@%") or vim.eval("fnamemodify(getcwd(), ':t')) returns a string, and it passes that string to find_pyproject_toml, which expects a sequence of strings, not a single string, and - since a string is a sequence of single character strings - it gets turned into a list of ridiculous paths. I tested with a file called foo.py, and added a print(path_srcs) into find_project_root, which printed out:

[PosixPath('/home/matt/f'), PosixPath('/home/matt/o'), PosixPath('/home/matt/o'), PosixPath('/home/matt'), PosixPath('/home/matt/p'), PosixPath('/home/matt/y')]                                                                  

So... that's wrong.

This seems to do the trick better than both the existing code and the proposed code:

diff --git a/autoload/black.vim b/autoload/black.vim
index f0357b0..0d93aa8 100644
--- a/autoload/black.vim
+++ b/autoload/black.vim
@@ -139,7 +139,8 @@ def Black():
       print(f'Reformatted in {time.time() - start:.4f}s.')
 
 def get_configs():
-  path_pyproject_toml = black.find_pyproject_toml(vim.eval("fnamemodify(getcwd(), ':t')"))
+  filename = vim.eval("@%")
+  path_pyproject_toml = black.find_pyproject_toml((filename,))
   if path_pyproject_toml:
     toml_config = black.parse_pyproject_toml(path_pyproject_toml)
   else:

This does work for an unnamed buffer, too - we wind up calling black.find_pyproject_toml(("",)), and that winds up prepending the working directory to any relative paths, so "" just gets turned into the current working directory.

Note that find_pyproject_toml needs to be passed a 1-tuple, not a list, because it requires something hashable (thanks to functools.lru_cache being used)

Given that no one on the core team (and who's active enough) is qualified to review vim PRs, I'm merging under the assumption godlygeek's approval is A-OK.