Confirmed, against d34e34f3e.
The replacement text of "utf8]{inputenc} \\usepackage[french, english"
makes it appear that the regex patterns used in
`org-latex-guess-babel-language' aren't sufficiently constrained. Checking
the regex, it's using "\\[.*\\]", which is why you're only seeing this when
you have more than one extra header (with only one, there's only one set of
braces).
I took a look and think I have a fix but I want a second opinion. The
attached patch fixes the regex by changing the greedy match for the
language to one that only captures what's between the "[...]". I tried
using a non-greedy qualifier (".*?") and that didn't work, but I feel like
I always get tripped up by Elisp regex patterns. If someone has a better
suggestion for the regex I'm open to changing it.
Owned.
Cheers,
Derek
On Wed, May 20, 2026 at 11:41 AM <[email protected]> wrote:
>
> With the following Org file
>
> ----------------------
> #
> * subtree
> :PROPERTIES:
> :EXPORT_LATEX_HEADER: \usepackage[utf8]{inputenc}
> :EXPORT_LATEX_HEADER+: \usepackage[french]{babel}
> :END:
>
> bak
> ----------------------
>
> upon subtree export (C-c C-e C-s lp), I get an error, the beginning of the
> backtrace of which is
>
> Debugger entered--Lisp error: (error "Invalid use of ‘\\’ in replacement
> text")
>
> org-latex-guess-babel-language("\\documentclass[11pt]{article}\n\n\n\\usepackage[utf8]{inputenc}
> \\usepackage[french]{babel}\n" (:export-options (subtree) :back-end
> #s(org-export-backend :name latex :parent nil :transcoders (... ... ... .
>
>
> This occurs with
>
> GNU Emacs 30.2 (build 1, x86_64-redhat-linux-gnu, GTK+ Version 3.24.43,
> cairo version 1.18.2) of 2025-08-18
>
> with either
>
> - a void .emacs and
>
> Org mode version 9.8.4 (9.8.4-2f6959 @
> /home/cochard/.emacs.d/elpa/org-9.8.2/)
>
> - a void .emacs and
>
> Org mode version 9.8.2 (9.8.2-2ef390 @
> /home/cochard/.emacs.d/elpa/org-9.8.2/)
>
> - emacs -Q and
>
> Org mode version 9.7.11 (release_9.7.11 @ /usr/share/emacs/30.2/lisp/org/)
>
> For what it's worth: (1) the problem does not show up for every combination
> of
>
> :EXPORT_LATEX_HEADER:
> :EXPORT_LATEX_HEADER+:
>
> (2) I did not succeed in exhibiting the problem with a single
>
> :EXPORT_LATEX_HEADER:
>
> --
> EOST (École et Observatoire des Sciences de la Terre)
> ITE (Institut Terre & Environnement) | [email protected]
> 5 rue René Descartes | Phone: +33 (0)3 68 85 50 44
> F-67084 Strasbourg Cedex, France | bureau 110, ancien bât.
>
>
--
+---------------------------------------------------------------+
| Derek Chen-Becker |
| GPG Key available at https://keybase.io/dchenbecker and |
| https://pgp.mit.edu/pks/lookup?search=derek%40chen-becker.org |
| Fngrprnt: EB8A 6480 F0A3 C8EB C1E7 7F42 AFC5 AFEE 96E4 6ACC |
+---------------------------------------------------------------+
0001-Fix-LaTeX-babel-language-detection-regex.patch
Description: Binary data
