[luatex] luatex problem with file with umlauts on windows 10

[Philip Taylor]

Ulrike Fischer wrote:
> Am Sun, 26 Apr 2020 11:00:50 +0100 schrieb Philip Taylor:
>
>> Trying to understand why Akira-san had written :
>>
>>>          local function is_texlive ()
>>>               local a = kpse.var_value ('command_line_encoding')
>>>               if a
>>>               then
>>>                     return true
>>>               else
>>>                     return false
>>>               end
>>>          end
>> rather than
>>
>>>          local function is_texlive ()
>>>               local a = kpse.var_value ('command_line_encoding')
>>>               return a
>>>          end
> because a is = "utf-8" and  not "true" in texlive.

Thank you Ulrike.  But if /within/ the function /is_texlive ()/ one can ask /if a/, where /a/ = "utf-8", why can one not ask that outside of /is_texlive ()/ ?  In other words, at the point of the call of /is_texlive ()/ [/if is_windows () and is_texlive ()/], why would a return value of "utf-8" not cause the /if/ to take the true branch, just as it does /within/ Akita-san's coding of /is_texlive ()/ ?
>> Could a Lua expert possibly explain why OFILE is reporting 'nil'
>> for "grüße.tex", please ?  Both are in the directory from which I
>> am issuing the TeXLua command.
> Because as Akira mentioned in a later posting kpse in a texlua
> script handles file names differently than kpse in a luatex
> document. You need to convert the file name before passing it to
> kpse.

Thank you, yes, spotted that after I asked the question.  But although my raw Lua can now open "grüße.tex", it reports a mangled name to the console, and also to the console within TeXworks.  This is all very messy !

/** Phil./
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