Re: M-- comment-region doesn't remove comment-padding when no more comment chars

[Stefan Monnier]

> In Emacs 20, M-- comment-region effectively undid the operation of
> comment-region, if given the right number as prefix arg. In Emacs 21, this
> is no longer the case.

> In Emacs 21, the comment chars are removed by M--, but the comment-padding
> is never removed. This requires users to perform an extra step of M-- C-x
> TAB to remove the extra padding inserted by comment-region.

> Example:

> C-u 5 comment-region on these lines in Emacs-Lisp mode:

> xxxxxxxx
> yyyyyyyy
> zzzzzzzz

> Result:

> ;;;;; xxxxxxxx
> ;;;;; yyyyyyyy
> ;;;;; zzzzzzzz

> M-- 5 comment-region results in this:

>  xxxxxxxx
>  yyyyyyyy
>  zzzzzzzz

> It should result in the original text:

> xxxxxxxx
> yyyyyyyy
> zzzzzzzz

Yes, it's a known "bug".  IIRC it hasn't been fixed because OT1H there wasn't
an easy way to fix it (i.e. it would make the code even more unmanageable),
and OTOH C-u M-x comment-region works as well.  I.e. the code assumes that
if you provide a negative numeric prefix you want to remove some but not all
the comment chars, since otherwise you'd have used C-u.


        Stefan