Am Fri, 28 Jul 2023 19:25:54 +0200 schrieb LARONDE Thierry:

>> Note that in order to do file testing by expansion (which we want for
>> various expl3 functions), we *have* to avoid \openin and that realistically
>> means \(pdf)filesize is the best option.
> 
> Why in this case not having requested a \filefind primitive,

Adding new primitives to all engines LaTeX supports is not easily
done, it can take a year or more and even if they are finally
implemented we would have to provide fallbacks for older engines.
So why should we do this work if a suitable primitive is already
present in all engines engines we test? 

Imho the question is more the other way round: why did you
implemented the primitive differently to the other engines? As you
explicitly document "but no extension is implicit" you must have
been aware that one must consider this case and that you are
deviating here.

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