BUG: posixpath.normal path returns invalid path on Windows

[bashtage]

Describe the bug

The use of posixpath.normalpath

in

        return (posixpath.normpath(rel_fn),
                path.normpath(path.join(self.srcdir, rel_fn)))

breaks windows builds when the source and build directory are not nested.

The reason this happen is that path.join inserts windows seperators that posixpath doesn't understand.

To Reproduce

Any project with a structure like

doc/ doc/source/conf.py doc/build/ <build dir>

breaks since this fix assumes that build is under source.

Heading into the function, rel_fn has a value like

bootstrap\\../../build/.doctrees/nbsphinx/bootstrap_bootstrap_examples_15_0.png

This needs to be converted to

../../build/.doctrees/nbsphinx/bootstrap_bootstrap_examples_15_0.png

which is the correct location but

is instead converted to

build/.doctrees/nbsphinx/bootstrap_bootstrap_examples_15_0.png

which is wrong.

Expected behavior
Get the correct path on windows so docs can build

Your project

https://github.com/bashtage/arch/tree/main/doc

Fix

The fix is to replace

posixpath.normpath(rel_fn)

with

posixpath.relpath(rel_fn, self.srcdir)

[bashtage]

An even better fix

Only change is to add in pathlib.Path(rel_fn).as_posix() to ensure that the window path looks like a posix path.

    def relfn2path(self, filename: str, docname: str = None) -> Tuple[str, str]:
        """Return paths to a file referenced from a document, relative to
        documentation root and absolute.

        In the input "filename", absolute filenames are taken as relative to the
        source dir, while relative filenames are relative to the dir of the
        containing document.
        """
        if filename.startswith('/') or filename.startswith(os.sep):
            rel_fn = filename[1:]
        else:
            docdir = path.dirname(self.doc2path(docname or self.docname,
                                                base=None))
            rel_fn = path.join(docdir, filename)

        return (posixpath.normpath(pathlib.Path(rel_fn).as_posix()),
                path.normpath(path.join(self.srcdir, rel_fn)))

[tk0miya]

I think your problem will be resolved by #8967. Could you check it please? If fine, I'll ship a bugfix release soon.
Thanks,