bug#74504: 31.0.50; Wrong source directory in *Help*

[Eli Zaretskii <eliz@gnu.org>]

> Cc: 74504@debbugs.gnu.org
> Date: Mon, 25 Nov 2024 18:26:12 -0500
> From:  Stefan Monnier via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> > 1. Build Emacs
> > 2. Run src/emacs -Q
> > 3. In the *scratch* buffer say M-x cd /tmp
> >    (/tmp here is just an arbitrary directory that is not the Emacs
> >    sources directory)
> > 4. C-h f make-overlay
> >    Now the first line in the *Help* buffer says:
> >    "make-overlay is a primitive-function in ‘C source code’."
> >    So far so good.
> > 5. Switch to the *Help* buffer and type s, this finds buffer.c
> > 6. Switch back to the *Help* buffer and type g
> >    The first line in *Help* now says:
> >    "make-overlay is a primitive-function in ‘/tmp/src/buffer.c’."
> >                                              ^^^^^ <-- Wrong!
> 
> Hmm... my code assumed the file was always absolute, but apparently
> that's not always the case.
> 
> The patch below seems to give us back the previous behavior, but maybe
> we should change some other part of the code so
> `help-fns-short-filename` is not used at all for the C sources (since
> it's specifically trying to give a name relative to `load-path`, which
> is nonsensical for our C files).
> 
> 
>         Stefan
> 
> 
> diff --git a/lisp/help-fns.el b/lisp/help-fns.el
> index c87c86bae84..266cf8eb4a9 100644
> --- a/lisp/help-fns.el
> +++ b/lisp/help-fns.el
> @@ -1052,7 +1052,8 @@ help-fns--radix-trees
>    "Cache of radix-tree representation of `load-path'.")
>  
>  (defun help-fns--filename (file)
> -  (let ((f (abbreviate-file-name (expand-file-name file))))
> +  (let ((f (abbreviate-file-name
> +            (if (file-name-absolute-p file) (expand-file-name file) file))))
>      (if (file-name-case-insensitive-p f) (downcase f) f)))
>  
>  (defun help-fns--radix-tree (dirs)

Ping!  Can we make further progress with this bug?