[luatex] \hyphenpenalty not working

[Élie Roux]

> As you inject discretionaries the best you can do is inject specific
> penalties (maybe combined with glue) as that is more predictable.

The problem is that if I do that, I have to make \pretolerance=-1, 
otherwise the cut will be after the discretionary (its third argument 
will be used), not "on" it (using its first and second arguments)... I 
don't know if you read luatex at tug.org, but I believe I have found what 
was going on:

http://tug.org/pipermail/luatex/2013-July/004516.html

> Anyhow, at first sight I see no issue with luatex (as we have clearly
> separated hyphenation, ligaturing and kerning stages there i trust
> luatex more).
>
> \showframe % \everypar{}
>
> \starttext
>
> \startbuffer
> % this cuts after the discretionary
> {aaaaab\discretionary{1}{2}{3}\penalty-10000cd\par}
> % this doesn't cut
> {aaaaab\discretionary{1}{2}{3}cd\par}
> % this cuts on the discretionary (both pdfTeX and LuaTeX)
> {\hyphenpenalty=-10000 aaaaab\discretionary{1}{2}{3}cd\par}
> % with pdfTeX: it cuts on the discretionary
> % with LuaTeX: it doesn't cut
> {aaaaab\discretionary{1}{2}{3}cd \par}
> \stopbuffer
>
> \dostepwiserecurse{30}{70}{1}
> {\hsize #1pt
> \framed[width=\hsize]{\the\hsize}\par
> \getbuffer
> \page}
>
> \stoptext
>
> Ok, one can see how \hyphenpenalty=-10000 controls the tolerance i.e.
> permits a bit more overflow but that's to be expected.

I have to say I cannot compile your example... but I definitely believe 
that if there is a change (\hyphenpenalty ignored during first attempt 
of line breaking), it should be documented in the manual... maybe there 
could be an option for it?

Thank you!
-- 
Elie