error if packages are loaded in a group

[u-fischer]

Brief outline of the bug

Packages should not be loaded in a group as this can lead to misbeheaviour that can be hard to detect or understand. As an example hyperref fails with an internal socket error if a group has been opened by mistake: https://github.com/latex3/hyperref/issues/315.

\usepackage and \RequirePackage should check the group level and error directly.

[github-actions[bot]]

This issue has been automatically marked as stale because it has not had recent activity.

[clason]

Sorry to be "that guy", but this broke font packages that conditionally require other packages based on package options (e.g., notomath). Is this known, and are there mitigation strategies?

[u-fischer]

@clason do you have an example where notomath breaks? I don't see a package loaded in a group there.

[clason]

Sure, give me a minute to extract the issue (it happens in a beamer theme).

[clason]

\documentclass{article}
\usepackage[sfdefault]{notomath}
\begin{document}
Test
\end{document}

The sfdefault option is what triggers the error:

This is pdfTeX, Version 3.141592653-2.6-1.40.26 (TeX Live 2024) (preloaded format=pdflatex)
 restricted \write18 enabled.
entering extended mode
(./style.tex
LaTeX2e <2024-06-01>
L3 programming layer <2024-05-08>
(/usr/local/texlive/2024/texmf-dist/tex/latex/base/article.cls
Document Class: article 2024/02/08 v1.4n Standard LaTeX document class
(/usr/local/texlive/2024/texmf-dist/tex/latex/base/size10.clo))
(/usr/local/texlive/2024/texmf-dist/tex/latex/notomath/notomath.sty
(/usr/local/texlive/2024/texmf-dist/tex/latex/base/fontenc.sty)
(/usr/local/texlive/2024/texmf-dist/tex/latex/fontaxes/fontaxes.sty)
(/usr/local/texlive/2024/texmf-dist/tex/latex/xkeyval/xkeyval.sty
(/usr/local/texlive/2024/texmf-dist/tex/generic/xkeyval/xkeyval.tex
(/usr/local/texlive/2024/texmf-dist/tex/generic/xkeyval/xkvutils.tex
(/usr/local/texlive/2024/texmf-dist/tex/generic/xkeyval/keyval.tex))))
(/usr/local/texlive/2024/texmf-dist/tex/latex/base/textcomp.sty)

! LaTeX Error: Loading a class or package in a group.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...

l.67 \usepackage
                {noto-serif}

Just ignoring that recurses and throws further (identical) errors there about packages required in noto-serif.sty (and packages required by those packages, and so on -- elephants all the way down).

(Let me know if I should open a new issue.)

[clason]

Seems to be this line in notomath.sty that is the culprit:

\ifnoto@sfdefault{\noto@MO{notosans}\else\noto@MO{noto}\fi

(which is defined by \newif\ifnoto@sfdefault \noto@sfdefaultfalse).

I don't quite see why, but commenting it out removes the error. (Voodoo debugging at its finest!)

[clason]

Oh, of course, that's a typo (missing brace closing the first clause). 🤦

Thanks for rubber-ducking, and sorry for wasting your time! Looks like this PR is doing its work already ;) I'll notify the maintainer.

[u-fischer]

well that is a clear bug in the package. The stray brace after \ifnoto@sfdefault shouldn't be there at all, and in earlier versions it would have lead to ### simple group (level 1) entered at line 54 ({). Notify the author.