Why is `openin_any = p` restricting access to packages in TEXMFDIST?

[Phelype Oleinik]

On Thu, Sep 24, 2020 at 5:56 AM Adrian <adrian at planetcoding.net> wrote:
>
> I see that you made a commit to change something in the logic there
> (unfortunately I can't reply directly to that email since I never received
> it; probably because it wasn't a directly reply to me and I'm not subscribed
> to the mailing list).
>
> Does that commit restore the old behavior about being able to use packages even
> with `openin_any = p`? At least the commit message sounds like it made checks
> more strict...

Hi Adrian,

With openin_any=p you can load most LaTeX packages normally.  The issue
specific to xparse(-generic.tex) is that it uses a \pdffilesize-based
(expandable) test to check whether a file exists, and as I said in my
previous mail, \pdffilesize fails with openin_any=p:

    export openin_any=p && pdftex '\pdffilesize{sample2e.tex}\bye'

and that's what Akira-san's patch addresses.

This "old behaviour" you mention is that until a few months ago xparse
was all loaded in one go in xparse.sty as most packages are (and work as
they always did), but now it is split into the "loader" (and legacy---do
not use---interfaces) and the bulk of the code in xparse-generic.tex.
Since the latter uses \pdffilesize, it fails with openin_any=p.

Best
Phelype