On 28/07/2023 16:14, LARONDE Thierry wrote:
> On Fri, Jul 28, 2023 at 03:58:49PM +0100, Joseph Wright wrote:
>> On 28/07/2023 15:28,  Thierry wrote:
>>> Yes. But the same engine does things differently between LaTeX
>>> 2022-11-01 and LaTeX 2023-06-01.
>>>
>>> So could someone give me the diff of the input related things in
>>> LaTeX between these two versions so that I can have a clue about
>>> what LaTeX is expecting and what it is eventually calling (because it
>>> could be calling, low level, the open routine, and there is no
>>> acrobatics made in the open routine in kerTeX: the handling is made
>>> before calling the routine; so if LaTeX is calling low level like
>>> this, the result is not a surprise).
>>
>> Older LaTeX used \openin + \ifeof to test for file existence; we now use
>> \(pdf)filesize, which is expandable and reports "0" for a non-existent file.
>> Both methods should find "foo.tex" from "foo" in the same way.
>>
> 
> Uh! You expect \filesize to do searching and file extension? Why?
> \filesize can be called with whatever file, not necessarily a .tex.
> Why would it assume it has to try an extension if it is not found?
> 
> Where was this specified for the primitive?

It's a TeX file-related primitive: they *all* are expected to 'read in' 
.tex, as they (should) all use the same underlying file operations. 
Otherwise, one would find that files are found by some mechanisms and 
not by others. One after all can \input things not ending in .tex, or 
\openin any file, but they both 'read in' .tex. (One can argue that at a 
primitive level this was not a great design choice, but it's what it is.)

Joseph