luatex problem with file with umlauts on windows 10

[Ulrike Fischer]

I have a problem with the lfs library in luatex and files with
non-ascii chars on window10:

This plain tex file 

\directlua{
function myfilesize(name)
  local file =  kpse.find_file(name, "tex", true)
  print("\string\nFILE: ",file)
  if file then
    local size = lfs.attributes(file, "size")
    local isfile= lfs.isfile (file)
    print("SIZE: ",size)
    print("isfile ", isfile) 
  end
end}
\input{grüße}
\directlua{myfilesize("grüße.tex")}
\bye


gives this output:

This is LuaTeX, Version 1.12.0 (TeX Live 2020/W32TeX)
 restricted system commands enabled.
(./test-utf8.tex (./grüße.tex)
FILE:   ./grüße.tex
SIZE:   nil
isfile  false
...

So the file "grüße.tex" is found fine by kpse and can be input, but
lfs doesn't access the size.

With miktex it works fine:

This is LuaTeX, Version 1.12.0 (MiKTeX 2.9.7400 64-bit)
 restricted system commands enabled.
(./test-utf8.tex (./grüße.tex)
FILE:   ./grüße.tex
SIZE:   5
isfile  true
...

Ascii-files works without problems. 


 
-- 
Ulrike Fischer 
https://www.troubleshooting-tex.de/