bug#41742: 28.0.50; Derive gnus-edit-form-mode from lisp-data-mode

[Eric Abrahamsen <eric@ericabrahamsen.net>]

"Basil L. Contovounesios" <contovob@tcd.ie> writes:

> Eric Abrahamsen <eric@ericabrahamsen.net> writes:
>
>> Hopefully this is fairly uncontroversial: Gnus has a gnus-edit-form-mode
>> for editing group parameters and other things, which presents the data
>> as elisp forms and is a perfect use-case for lisp-data-mode -- turning
>> on paredit or what have you. This patch derives the former from the
>> latter.
>
> LGTM, FWIW.
>
> While there, would you mind cleaning up how gnus-edit-form-mode-map is
> defined?  It currently does a defvar+unless+setq dance, whereas it
> should ideally only be a defvar+let, as per the last few paragraphs of
> (info "(elisp) Tips for Defining").

Huh, the last few paragraphs of that info page make it look like it's
_okay_ to do defvar+unless+setq, am I misreading this? Granted it only
says to do it so you can get the docstring closer to the defvar, and
there's no docstring in this case, but it does seem acceptable.

I wonder what the point of writing it this way is, otherwise?