bug#57325: 27.1; functions in ff-other-file-alist

[Felician Nemeth <felician.nemeth@gmail.com>]

Eli Zaretskii <eliz@gnu.org> writes:

> AFAICT, what you saw is the consequence of one basic problem:
> ff-find-the-other-file is unprepared to deal with a function that
> returns nil (instead of a list of file-name extensions to try).  So it
> tries to use that nil value as if it was a list of extensions, and the
> result is basically random.
>
> It should be easy to make ff-find-the-other-file detect the nil value
> and handle it as if it found no match for the current buffer's file.
> Do you think this would be better?  Or we could simply document that a
> function in ff-other-file-alist must return a list of extensions.
>
> WDYT?

I think extending the documentation to explain what is expected from the
function is enough.  It would have helped me.  Also, when the function
returns an absolute file name, then the returned file should be already
opened, otherwise ff-find-other-file cannot find it.

Thank you.