(Please keep me CC'd as I'm not subscribed to the list)

Hi, I'm the lua-widow-control author.

> lua error > lua error on line 74 in file
> /opt/luametatex/texmf-modules/tex/context/third/lua-widow-control/t-lua-widow-control.mkxl
> The odd thing is that line 75 of the t-lua-widow-control file is empty.

The \setuplwc command ends on line 74, which then triggers \everysetuplwc which then calls \ctxlua{lwc.enable_callbacks()}. This fails since lwc is undefined because the Lua file isn't loaded because ConTeXt can't seem to find the file.

In Plain LuaTeX and LuaLaTeX, a missing Lua file is a fatal error:

    $ luatex "\nonstopmode\directlua{require 'not-a-real-file'}\bye"

    This is LuaTeX, Version 1.13.2 (TeX Live 2021/W32TeX)
     restricted system commands enabled.

    [\directlua]:1: module 'not-a-real-file' not found:
            no field package.preload['not-a-real-file']
            [kpse lua searcher] file not found: 'not-a-real-file'
    stack traceback:
            [C]: in function 'require'
            [\directlua]:1: in main chunk.
    <*> \nonstopmode\directlua{require 'not-a-real-file'}
    (see the transcript file for additional information)
    warning  (pdf backend): no pages of output.
    Transcript written on texput.log.

so I'm a little surprised that ConTeXt just issues a warning here when it can't find the file:

   resolvers > lua > unknown file 'lua-widow-control.lua'

> when it says it doesn't know the lua-widow-control.lua file. I don't see
> any mention of this file within the t-lua-widow-control module.

lua-widow-control.lua is loaded at line 63 of the .mkxl:

> Could it be that this module is not yet mature for lmtx

Lua-widow-control is certainly more stable with Plain/LaTeX, but it usually runs fine with LMTX. The entire lwc manual is written in ConTeXt/LMTX so I (usually) notice pretty quickly when things break.

The only real "issue" with LMTX is that the engine changes pretty quickly, so lwc may sometimes be broken for a few days between an engine update and whenever I push out a fix. This doesn't happen with Plain/LaTeX since the LuaTeX engine is mostly frozen.

Interestingly, the MkXL version of lwc actually predates the MkIV version, although only by a few months.

> I have \usemodule[lua-widow-control] in my tex document, and
> I haven't forgotten to do the prescribed mtxrun --generate after
> including the module in my third-party folder of my luametatex
> installation on Arch.

Hmm, that's odd then. I'm not entirely sure why this is happening, so I'm going to take a random guess:

Maybe you installed lwc using a zipfile from either GitHub or the ConTeXt Garden modules site, then you copied the files into your texmf-modules/ folder, *but* you only copied the "tex/context/" folder and not all of the folders in the "tex" folder. The "lua-widow-control.lua" file is in the "tex/luatex/" folder, so if you didn't also copy that across you're going to have problems.

Again, just a random guess. If that doesn't work, you could maybe try running
    context --make
but I doubt that that would fix anything here. You could also try deleting the filename cache files at:
then rerunning
    mtxrun --generate
I've never deleted those files before, but it's in a folder called "cache" so it's _probably_ safe to delete (make a backup just in case though).

If none of that works, then the issue could be something else on your end, or I could have screwed something up in lwc. In that case, try running
    find /opt/luametatex/texmf-modules/ -path '*widow*' -print
    mtxrun --find-file lua-widow-control.lua
and reply with the output.

Oh, and one more note. ConTeXt version "2022-04-11 19:20" renamed some of the engine Lua functions, so make sure to update to lwc v2.0.6 (if you're using a recent ConTeXt version). Otherwise after you fix the "unknown file" error, you would get an "attempt to call a nil value" error which isn't any better.

Let me know if you have any other issues.

 -- Max
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