bug#7751: 24.0.50; `fill-paragraph' on doc string with colons

[Lawrence Mitchell]

Drew Adams wrote:
> This is a regression introduced in Emacs 22.1.  There is no such problem
> in Emacs 20 or 21.

[...]

> The same problem occurs if you change "allowed:" to "allowed.",
> "allowed!", "allowed?", "allowed,", or just "allowed", and no matter how
> much space you leave after it.  The same problem occurs if you remove
> "allowed:" altogether, i.e., with "The usual menu keywords are :enable,
> ...".

Here's an even more minimal test-case:

emacs -Q

(setq emacs-lisp-docstring-fill-column 30)
(insert "\"a word, another word and more :bar\"")

M-q

gives a break of:

| a word, another word and
| more :bar

whereas one would expect

| a word, another word and more
| :bar


The problem appears to be in the regexp used to define
paragraph-start in lisp-fill-paragraph:

...
      (let ((paragraph-start (concat paragraph-start
                                     "\\|\\s-*\\([(;:\"]\\|`(\\|#'(\\)"))
...

Removing the colon leads to "expected" line breaking.

FWIW, the colon was introduced by this commit:

commit cd3f5084abdd59a8392cedee90ddbaa096d61d55
Author: Dave Love <fx@gnu.org>
Date:   Wed Mar 18 16:02:37 1998 +0000

    (lisp-fill-paragraph): Adjust
    paragraph-start in default filling case so that filling doc
    strings works.

Cheers,

Lawrence
-- 
Lawrence Mitchell <wence@gmx.li>