bug#69404: Loss of latex-mode fontification when loading libraries in latex-mode-hook that require json-mode

[Gabriele Nicolardi]

Hi,

my actual scenario involves using latex-mode-hook to load some libraries that require json-mode.

I replicated my issue in a MWE:

I have a LaTeX file:

\documentclass{article}
\usepackage{mwe}
\begin{document}

\blindtext

\noindent
\includegraphics[width=.4\textwidth]{example-image-a}\hfill
\includegraphics[width=.4\textwidth]{example-image-b}

\blindtext

\end{document}

If I load it like this:

emacs -Q test.tex

I get this “correct” latex-mode fontification:

I have also a config file (I simplified it to obtain the feature):

(add-hook 'latex-mode-hook
          #'(lambda ()
          (package-initialize)
          (require 'json-mode)))

If I load my .tex file like this:

emacs -Q --eval "(load-file \"/tmp/config.el\")" test.tex

I lose latex-mode fontification:

1. In the last case, to restore correct latex-mode fontification I need to do M-x latex-mode
2. This problem does not happen with other packages or custom libraries but, in my experience, it happens only for the json-mode package.
3. If I load json-mode “before” latex-mode I have no problem. E.g. if I modify the config.el file this way:

(package-initialize)
(require 'json-mode)

and I do:

emacs -Q --eval "(load-file \"/tmp/config.el\")" test.tex

I get the correct latex-mode fontification.

Am I doing something wrong or is it some kind of bug in json-mode or in Emacs?

Important note. This didn’t happen with previous versions of Emacs. Before upgrading to version 29.2, I was using version 27 and never encountered this issue prior to the upgrade.

(I opened an issue on StackExchange where you can find the formatted version, with figures, of this message: https://emacs.stackexchange.com/q/80447/15606)

Best regards,

Gabriele Nicolardi

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