bug#67937: 30.0.50; auth-source-pass relies on epa-file being enabled

[Michael Albinus via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Arsen Arsenović <arsen@aarsen.me> writes:

> Hi Michael,

>> No, auth-source-pass should not enable it on its own I believe. It
>> should fire an error, which hopefully produces a backtrace. This
>> backtrace would help us to understand, what's up.
>
> I doubt that it would produce a useful backtrace, because I doubt a
> well-behaved let-binding is causing an error (as I said, when I notice
> this bug, epa-file stops working everywhere, even long after a potential
> let-binding would've been unbound, implying that it gets unset via some
> other means).

But we shall try it.

> Nonetheless, it is worth a shot.  I will inject a check into my
> currently running Emacs and see what happens.
>
> I think erroring is an acceptable solution, though (but I do not think
> the same of returning nil).

Would be OK for me. Please add a hint to the error, that the user shall
contact the Emacs department about. In case your patch arrives the repository.

> I'm also not sure how complex the heuristic for emitting this error
> would be.  (memq epa-file-handler file-name-handler-alist) is not
> adequate as non-EPA handlers for PGP files could be active and/or
> preferred.

Well, it could be a starter. As you said, you have observed
file-name-handler-alist being nil, so this test would be good enough for now.

We have also (find-file-name-handler FILENAME 'insert-file-contents)
But the interpretation of the result is a little bit more tricky.

> I'm willing to implement a solution if you know a better heuristic.

Let's start with what we have. Thanks!

> Thanks, have a lovely day.
>
> Arsen Arsenović

Best regards, Michael.