Change to output routine code breaks latex afterpage package

[David Carlisle]

A similar test



\def\xxx{\aftergroup X\global\let\xxx\relax}

\output{\xxx\plainoutput}

AAA

\break

BBB

\bye




previously X appeared on page 2, now X is lost and does not appear.

David


On Sun, 24 Mar 2024 at 19:54, Frank Mittelbach <
frank.mittelbach at latex-project.org> wrote:

> Am 24.03.24 um 20:47 schrieb David Carlisle:
> >
> > It appears that the change
> >
> >
> >
> https://github.com/TeX-Live/texlive-source/commit/d17e5e0968269f781f3fe972b705fff43ea2e139
> <
> https://github.com/TeX-Live/texlive-source/commit/d17e5e0968269f781f3fe972b705fff43ea2e139
> >
> >
> > avoid crashing on devious uses of \output and write braces, from DRF …
> >
> > breaks the afterpage package that has been part of the core latex2e
> > release since the start.
> >
> > see
> >
> > https://github.com/latex3/latex2e/issues/1311
> > <https://github.com/latex3/latex2e/issues/1311>
> >
> > Can this be reverted/adjusted so the package still works?
> >
> > \documentclass{report}
> > \usepackage{afterpage}
> > \begin{document}
> > Page \thepage
> > \afterpage{Hi!}
> > \newpage
> > Page \thepage
> > \newpage
> > Page \thepage
> > \end{document}
> >
> > produces 3 pages  with Hi on page 2 in all previous releases, but
> > produces 4 pages with Hi on page 4 in tl2024
>
>
> Basically it seems that the change  stops \aftergroup working inside the
> OR, i.e., an \aftergroup in the output routine is simply lost instead of
> being executed after the output routine has ended.
>
> Example, based on the example given in the commit:
>
> \catcode`\{=1 \catcode`\}=2
> \def\makepage{
>   \hrule width 2in height 1in
>   \vskip 1in plus 10in
>   \hrule width 2in height 1in
>   \penalty-10000
> }
> \output{\global\advance\count0 by 1 \shipout\box255\extra}
> \let\lb={
> \let\rb=}
> \message{RELAX}
> \let\extra=\relax
> \makepage
> \message{DONE_RELAX}
> \message{AFTERGROUP}
> \def\extra{\aftergroup\foo}              % <--- this should produce a
>                                           %      undefined error later
> \makepage
> \message{DONE AFTERGROUP -- foo lost}    % <--- but it doesn't
> \message{AFTERGROUP 2}
> \def\extra{\aftergroup\foo}
> \def\foo{\aftergroup\foofoo}
> \makepage
> \message{DONE AFTERGROUP 2 -- foo lost}
> \message{EXTRA_RIGHT_BRACE}
> \let\extra=}
> \makepage
> \message{DONE_EXTRA_RIGHTBRACE}
> \message{EXTRA_LEFT_BRACE}
> \let\extra={
> \makepage
>
>
> --------
>
> frank
>
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