bug#31558: 27.0; `custom-file' settings messed up by Emacs 27

[Michael Albinus]

Drew Adams <drew.adams@oracle.com> writes:

Hi Drew,

>> Maybe you put at the beginning of your custom file
>> (or (locate-library "tramp") (provide 'tramp))
>
> Yes, I guess that would work and is better than nothing,
> but it seems wrong to tell Emacs that something has
> been provided that has not. ;-)
>
> Worse than style or ugliness, though, is that there
> might be code here or there that tests
> (featurep 'tramp) and acts accordingly.  That code
> surely will be led astray by such a hack.

We're spaeking about Emacs < 22. How many such Emacsen are in use today,
which also use packages checking for Tramp?

> Seems like there should be a way for Tramp and
> Customize to collaborate to produce a conditional
> sexp that does not require tramp unconditionally.
> E.g., one that tests (at time of evaluating
> `custom-set-variables') whether Tramp is even
> included in the Emacs version.
>
> Or maybe somehow just use a soft-require - the
> equivalent of (require 'tramp nil t)?  Would that
> work for Tramp, if it were possible for
> `custom-set-variables'?
>
> Seems like something is missing from Emacs for
> such cases.  A library wants to ensure that it is
> loaded before evaluating a sexp that sets one of
> its user options.  But if loading the library is
> impossible then setting the variable is benign,
> so a soft-require is all that is really needed.

If there were such a possibility I would consider it. But it must
already exist for Emacsen < 22; I doubt we will change them if it's not
possible yet.

And given the low likelihood plus the existing workaround, I believe it
is not worth to spend time for this. Sorry.

Best regards, Michael.