[tex-live] TL'18: LuaTeX and Lua version

[Joseph Wright]

Hello all,

As binary building for TL'18 has started, I've been testing LuaTeX v1.07 
against the LaTeX kernel test suite (using the W32TeX binaries: thanks 
Akira). Currently, I believe the plan is that TL'18 will use LuaTeX with 
Lua 5.2 with a second binary for Lua 5.3 for testing.

I can understand the desire for stability in the Lua version, but at the 
same time I'm not sure how much testing Lua 5.3 will get here. To use it 
you'll need to select the right binary, which at least as I understand 
it will be plain/iniTeX only, making using LaTeX with it a bit more 'fun'.

I've gone for the approach of simply swapping my luatex.dll and 
rebuilding everything, which works for me but isn't that general. At the 
same time, my understanding of the Lua 5.3 changes is that they are 
largely quite specialised, and at least in initial testing don't break 
e.g. luaotfload.

I wonder if

- There is a need to not simply make the change and use LuaTeX with
   Lua 5.3
- That being the case, if a mechanism to 'swap' what version
   "luatex"/"lualatex" point to could be arranged (symlinks/swapping
   .dlls/whatever)

Joseph