Short columns with columnbreak in multicol* disappearing after first page, except for last column

[jeremy-engel]

Brief outline of the bug

This issue is a possible extension of the problem discussed in #11. In that issue, in a multicol environment, content could overlap on the final page if the \columnbreak macro was used in enough places in which the content without the breaks could fit on a single page.

This issue relates to the multicol* environment. In a similar situation, when there are shorter columns and column breaks, the first page of the environment prints fine, but all of the columns except for the last one are not output, and the final column is by itself on the final page. The minimal example below is an extreme case representing the issue.

I first noticed after installing TeX Live 2018, and it looks to be the result of the fix for #11. It isn't a major issue since it is easy to not be in this position in the first place (either by simply using the balanced columns or by boxing and measure content to decide when column breaks are absolutely necessary), but I thought I would report anyway since it was hard to notice it was happening, especially with existing documents, and it was a bit confusing what was really going on until I found the related issue.

Minimal example showing the bug

\RequirePackage{latexbug}
\documentclass{article}

\usepackage{multicol}

\begin{document}

\begin{multicols*}{2}

\columnbreak
column 1

\columnbreak
column 2

\columnbreak
column 3

\columnbreak
column 4

\columnbreak
column 5

\columnbreak
column 6

\columnbreak
column 7

\end{multicols*}

\end{document}

Log file (required) and possibly PDF file

Log and PDF in TeX Live 2018 with most recent multicol:

unbalanced columns test.log
unbalanced columns test.pdf

Log and PDF in TeX Live 2017 before multicol was updated for the referenced issue:
unbalanced columns test with tex live 2017.log
unbalanced columns test with tex live 2017.pdf

[FrankMittelbach]

thanks for the report. multicols* was dropping the end environment penalty if the page overflowed. Should be fixed with 6da3db0. If you could check that would be great.

[jeremy-engel]

That commit resolves the issue in the original document that led to the example above. Thanks!

[FrankMittelbach]

ok so this will go into the next tools distrib (not sure when that will be though)