Output normalization hook

[muzimuzhi]

To apply additional normalization, after built-in output normalization is done. Could be named normalize_hook().

Use case: to simplify specific test output, for example the log-based m3plain002.lvt test in latex3, added in latex3/latex3#1467

latex3/latex3#1467 (comment):

Commit 6f301f1 adds a plainTeX test that loads expl3-generic.tex in a group with \tracingrestores turned on. I think it dumps too many lines hence am considering dropping it in final state.

Is there a way to track lines containing =undefined} only? If so, I'm willing to keep m3plain002.lvt.

[cfr42]

This would be useful for testing font packages because it would let me remove glue/box lines. (I could post-process the output with something like sed or perl, much as @davidcarlisle suggested, but that means abandoning cross-platform/cross-distribution compatibility.) As far as I know there's no tracing option for pdfTeX/TeX which will give me (all) the font lines I want without the lines I don't. Right now the only cross-platform options appear to be to rewriting the normalisation function or tolerating the 'noise'.

[josephwright]

I think before doing this we maybe should refactor the normalisation code anyway. We used to worry about long lines, but the 'plan' has changes so we run with a very large line length and avoid that. So perhaps we should make the latter a requirement, simplify the normalisation, then look at this?

[muzimuzhi]

We used to worry about long lines, but the 'plan' has changes so we run with a very large line length and avoid that.

But that's configurable and I've seen cases where package maintainers chose to set the old value of maxprintline, for example tuna/thuthesis@45c0b37. So maybe existing normalisation code for wrapped long lines should be kept. Or it can be turned off if maxprintline ~= 9999.

[josephwright]

We used to worry about long lines, but the 'plan' has changes so we run with a very large line length and avoid that.

But that's configurable and I've seen cases where package maintainers chose to set the old value of maxprintline, for example tuna/thuthesis@45c0b37. So maybe existing normalisation code for wrapped long lines should be kept.

Indeed - that's why I said about making it a requirement - we can't simplify the normalisation unless we also force the line length. That's a breaking change but over time we have made those where it makes sense - it's not hard to update .tlg files when one knows the only change is in l3build. But that is likely a separate discussion to the question of a normalisation hook.