bug#2355: 23.0.60; Enabling minor-mode disables major mode

[Stefan Monnier]

> That is, indeed, what causes the difference in behavior. BTW,
> lisp/doc-view.el abuses it:

>  ;; Local Variables:
>  ;; mode: outline-minor
>  ;; End:

This seems like a misuse because it just reflects the
author's preference.

>> It would be good to fix those discrepancies.
> I don't think investing effort in fixing wrong (harmless) behavior
> caused by user error is very useful...

I do not plan on investing any effort into it.  But a patch would
probably be welcome, if it doesn't make the code more complex.

>> But it would also be good to improve the documentation so as to say
>> clearly that at least one of the `mode's specified should be
>> a major mode.

> You seem to be implying that it is OK to use mode: to set a minor mode.

Yes, it is.

> That seems to contradict the docs, at least my reading of
> (emacs)"27.1 How Major Modes are Chosen" and (emacs)"57.3.4.1
> Specifying File Variables".

My 57.3.4.1 here says:

      You can use the `mode' "variable" to set minor modes as well as the
   major modes; in fact, you can use it more than once, first to set the
   major mode and then to set minor modes which are specific to particular
   buffers.  But most minor modes should not be specified in the file at
   all, because they represent user preferences.


-- Stefan