bidi package fail with recent version of multicol

Question

I have this simple example of multicol in RTL document with bidi package. Version of multicol package in my TL2021 is 1.9b result after compilation with xelatex is incorrect

\documentclass{article}
\usepackage{multicol}
\usepackage{lipsum}
\usepackage[rldocument]{bidi}

\setlength\columnseprule{0.4pt}

\begin{document}

\begin{multicols}{2}
\lipsum
\end{multicols}

\end{document}

Answer 1

As mentioned in my comment this is due to fixes that have been done to internal commands of multicol and which are not reflected (so far) in the patches done by bidi.

As a temporary fix if it turns out that Ulrike's suggested patches aren't sufficient, you can roll back multicol individually as follows (unfortunately you have to go a long way back as I didn't add a rollback for 1.8).

Try this:

\usepackage{multicol}[=2018-01-01]

in your documents until the time bidi gets updated.

Answer 2

You could try this (but there is lots of guessing involved, so I don't know if it will also work in more complicated cases):

\documentclass{article}
\usepackage{multicol}
\usepackage{lipsum}
\usepackage[rldocument]{bidi}

\setlength\columnseprule{0.4pt}
\usepackage{etoolbox}
\makeatletter
\patchcmd\LTR@column@boxes{\mult@gfirstbox}{\mult@firstbox}{}{\fail}
\patchcmd\RTL@column@boxes{\mult@gfirstbox}{\mult@firstbox}{}{\fail}
\patchcmd\RTL@column@boxes{\mult@gfirstbox}{\mult@firstbox}{}{\fail}
\makeatother

\begin{document}

\begin{multicols}{2}
\lipsum
\end{multicols}

\end{document}