bug#32643: 26; minor-mode variables

[Drew Adams <drew.adams@oracle.com>]

>   > It doesn't say why some do and some don't.  Why doesn't it?  What's the
>   > answer to that question?  For example, why doesn't variable
>   > `auto-fill-mode' exist?  Shouldn't all minor modes have a variable?
>   > Which ones should?
> 
> It is not crucial for the manual to answer "why" questions.
> If this one were easy to answer, it could be worth answering.
> But in fact this one would be a lot of work.

I get that you replied only about that intro paragraph. And no,
it's not "crucial" to explain "why" about everything. Far from it.

And I guess you're only speaking against any blanket requirement
to explain "why" everywhere, and not against a request that
`auto-fill-mode' have a variable etc.

But the real point of the bug report is that we _do_ say that a
minor mode should have (and set) a mode variable:

  Define a variable whose name ends in '-mode'.  We call this the
  "mode variable".  The minor mode command should set this
  variable.

And that "should" is not respected by some variables from basic
Emacs itself - in particular `auto-fill-mode'. Shouldn't it be?

Nothing requires everything in the Emacs distribution to respect
each convention that Emacs sets forth. But is there a reason why
`auto-fill-mode' (and others?) should not respect this convention?
If nothing else, I'm curious why the exception(s).

(The bug report also asks whether it's a bug for a mode not to have
a variable, and suggests that it is. And if it's not, the report asks that
the Elisp manual give some guidance about when a mode should
not or need not have a variable.)