Error during luaotfload font name database creation

Question

I got an error on a new MiKTeX 2.9 win7 64-bit install while running the luaotfload tool.

luaotfload | Updating the font names database:
luaotfload | Font names database not found, generating new one.
      This can take several minutes; please be patient.
luaotfload | Updating the font names database:
<omitted>
The network name cannot be found.
Data: \\MiKTeX\]MPM[\fonts\opentype

The error is very cryptic and is very similar to

LuaTeX font database cannot be created in MiKTeX 2.9

Unfortunatly that topic was unanswered. However, I dug a little deeper and found the real cause. The $OPENTYPEFONTS path in MikTex is set to (among other things) '%R\fonts\opentype//'

Now I checked expanding this path using

kpsewhich --expand-path='%R'

and I get the same error. But if I use a small letter r

kpsewhich --expand-path="%r" 

it works perfectly fine.

How do I make kpsewhich case-insensitive or update the $OPENTYPEFONTS variable to have a small %r

Answer 1

I came across the same problem and tried to implement your solution. Maybe someone knows a more elegant way, but it works for me now: In every affected Lua file in the directory tex/latex/luaotfload (for me: luaotfload-configuration.lua, luaotfload-database.lua, luaotfload-diagnostics.lua and luaotfload-parsers.lua) you have to replace the line

local kpseexpand_path = kpse.expand_path

by

local kpseexpand_path = function (p) return kpse.expand_path(string.gsub(kpse.expand_var(p), '%%R', '%%r')) end

It expands the variables $OPENTYPEFONTS and the others, but replaces %R by %r before that is expanded in turn. As far as I can tell from the MiKTeX source code, the appearance of %R in $OPENTYPEFONTS is hard-coded, so this is the only way I could find without recompiling MiKTeX...