\AtBeginDocument documentation

[jlaurens]

Brief outline of the bug

The documentation of \AtBeginDocument is inaccurate. In particular, using \AtBeginDocument after \begin{document} is not allowed, contrary to \AddToHook{begindocument}.

Minimal example showing the bug

\RequirePackage{latexbug}       % <--should be always the first line (see CONTRIBUTING)!
\documentclass{article}
\begin{document}
\AtBeginDocument{FOO}
\AddToHook{begindocument}{BAR}
\end{document}

Log file (required) and possibly PDF file

This is pdfTeX, Version 3.141592653-2.6-1.40.26 (TeX Live 2024) (preloaded format=pdflatex)
 restricted \write18 enabled.
entering extended mode
(./trashme.tex
LaTeX2e <2024-06-01> patch level 1
L3 programming layer <2024-05-27>
(/usr/local/texlive/2024/texmf-dist/tex/latex/latexbug/latexbug.sty)
(/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/l3backend/l3backend-pdftex.def)
(./trashme.aux)

! LaTeX Error: Can be used only in preamble.

See the LaTeX manual or LaTeX Companion for explanation.
Type  H <return>  for immediate help.
 ...                                              
                                                  
l.6 \AtBeginDocument
                    {FOO}
? 

[1{/usr/local/texlive/2024/texmf-var/fonts/map/pdftex/updmap/pdftex.map}]
(./trashme.aux) )</usr/local/texlive/2024/texmf-dist/fonts/type1/public/amsfont
s/cm/cmr10.pfb>
Output written on trashme.pdf (1 page, 11980 bytes).
SyncTeX written on trashme.synctex.gz.
Transcript written on trashme.log.

[FrankMittelbach]

Which documentation are you referring to?

[jlaurens]

lthooks-doc.pdf from texdoc lthooks