Normalise font file paths in XeTeX log messages

[moewew]

While trying to make more use of l3build for biblatex I encountered an issue with XeTeX log comparison: Some file paths are not normalised away (https://github.com/moewew/biblatex/runs/5350350889?check_suite_focus=true). I set up a small example at https://github.com/moewew/buildxetex to demonstrate the problem. Essentially the issue is that a font-switching example such as

\input{regression-test}
\documentclass[a4paper]{article}
\usepackage{fontspec}
\usepackage{libertine}
\usepackage[fallback]{xeCJK}
\begin{document}
\showoutput
\START
Lorem

章學成

ipsum

\clearpage
\OMIT
\end{document}

has something like

Requested font "[FandolSong-Regular.otf]/OT:language=dflt;" at 10.0pt
 -> /home/m/texlive/texmf-dist/fonts/opentype/public/fandol/FandolSong-Regular.otf

in the output.

Would it be possible to normalise these file paths away?

In any case I would also not mind additional hints as to how to make this comparison more robust.

[josephwright]

The trick we typically use for font issues is to have some throw away content to load them, then \newpage before \START, so those lines are simply dropped.

I will of course think about how to pick up these cases.

[moewew]

Thanks for that idea. I ended up doing https://github.com/plk/biblatex/commit/59e342b587c8d7e512e5ac4de56cd8f9f5bfda25 for now, it ain't pretty, but it works.

[FrankMittelbach]

blame it on the fact that all engines write things differently into the log :-( ... we do our best but there are always the odd cases left