bug#81606: Mojibake with UTF-8 file names

Eli Zaretskii <[email protected]> writes:

> I can add it to "TeX Print", where the tex-main-file variable is
> documented.  Is that okay?

Yes, it seems to be the correct place.

> And I still don't think we have a consensus regarding the fix for
> latexenc.el: do we want to decode using UTF-8 or 'undecided'?

My preference is in this message:

  https://lists.gnu.org/archive/html/bug-gnu-emacs/2026-08/msg00877.html

The second paragraph should read:

  My vote is to go for the utf-8 variant since LaTeX is pushing users in
  that direction anyways and newer engines like LuaTeX require it.

@Werner: Can you please do me a favor and try the following:

• Save the 2 files in a temp directory
• Start Emacs as 'emacs -Q'
• Open 'ä-include.tex' and hit 'C-h m' and make sure you see:

  The major mode is LaTeX mode defined in tex-mode.el

• And now hit 'C-c C-f' to run `tex-file'.  This is what I see:

--8<---------------cut here---------------start------------->8---
$ latex \\nonstopmode\\input \ä.tex
This is pdfTeX, Version 3.141592653-2.6-1.40.29 (TeX Live 2026) (preloaded format=latex)
 restricted \write18 enabled.
entering extended mode
LaTeX2e <2026-06-01>
L3 programming layer <2026-07-20>

(/usr/local/texlive/2026/texmf-dist/tex/latex/tools/.tex File ignored)

! LaTeX Error: Missing \begin{document}.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              
                                                  
<*> \nonstopmode\input ä
                         .tex

LaTeX Font Warning: Font shape `/cmr/m/n' undefined
(Font)              using `/cmr/m/n' instead on input line 0.

! Corrupted NFSS tables.
wrong@fontshape ...message {Corrupted NFSS tables}
                                                  error@fontshape else let f...
<*> \nonstopmode\input ä
                         .tex

LaTeX Font Warning: Font shape `/cmr/m/n' undefined
(Font)              using `OT1/cmr/m/n' instead on input line 0.

Missing character: There is no . in font nullfont!
Missing character: There is no t in font nullfont!
Missing character: There is no e in font nullfont!
Missing character: There is no x in font nullfont!
! Emergency stop.
<*> \nonstopmode\input ä.tex
                             
No pages of output.
Transcript written on .log.
--8<---------------cut here---------------end--------------->8---

In case you see the same thing, then this is an issue which possibly
deserves another bug report.  I'm on macOS.

Best, Arash