bug#71500: 28.2; Can't create/open .gpg file name contains non-ascii encoding in windows

[Eli Zaretskii]

> Date: Fri, 28 Jun 2024 20:30:08 +0900
> From: Kazuhiro Ito <kzhr@d1.dion.ne.jp>
> Cc: billy.hotwind@gmail.com, eliz@gnu.org
> 
> > Ping!  Did you have a chance to try Emacs 30 (now on the emacs-30
> > branch of the Emacs Git repository)?
> 
> Unfortunately, the issue is not resolved.
> 
> As Tatsuya wrote, epg--start function calls gpg2 program with setting
> :coding property to raw-text, thus each argument should be encoded in
> proper coding system by a caller.  The problem would occur on any OS
> whose file name coding system was not utf-8.
> 
> For example, in case of epg-decrypt-file, following change is required
> if we need to set :coding property to raw-text for ENCODING.
> 
> diff --git a/lisp/epg.el b/lisp/epg.el
> index 7bec91f616d..59870761565 100644
> --- a/lisp/epg.el
> +++ b/lisp/epg.el
> @@ -1468,7 +1468,10 @@ epg-decrypt-file
>        (progn
>       (setf (epg-context-output-file context)
>                (or plain (make-temp-file "epg-output")))
> -     (epg-start-decrypt context (epg-make-data-from-file cipher))
> +     (epg-start-decrypt context
> +                           (epg-make-data-from-file
> +                            (encode-coding-string
> +                             cipher file-name-coding-system)))
>       (epg-wait-for-completion context)
>       (epg--check-error-for-decrypt context)
>       (unless plain

Thanks, but this doesn't look right to me.  The problem is likely in
the fact that epg--start sets the encoding/decoding for the epg
process to raw-text in a way that is too broad: it affects not only
how we encode and decode text sent to and received from GnuPG, but
also how its command-line arguments are encoded.  And that's not what
we want.

So I think the right fix is in epg--start: instead of setting :coding
as part of the make-process call, it should call
set-process-coding-system _after_ the make-process call, so that
raw-text will affect only the text we send and receive from gpg.

Can you try such a change and see if it fixes the problem?