Filling of Haddock comments is broken

[khumba]

Set fill-column to 80 and try filling the following comment with M-q:

-- | asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf asdf 1234 5678
-- 90ab
main :: IO ()

Despite the first line being longer than 80 characters, it won't move 5678 to the next line. If you remove the leading |, or remove the whole 90ab line, it will wrap, but if the comment already has multiple lines, it won't.

(haskell-version) reports haskell-mode 13.15-git (/home/khumba/.emacs.d/elpa/haskell-mode-20150904.1344/), and this is on NixOS 14.12. The only thing for haskell-mode in my ~/.emacs is:

(add-hook 'haskell-mode-hook 'turn-on-haskell-indentation)

[gracjan]

Thanks for the report. Can you add this as a test case in tests directory?

[khumba]

On Sat, 05 Sep 2015 23:46:07 -0700
Gracjan Polak notifications@github.com wrote:

Thanks for the report.

Can you add this as a test case in tests directory?

Sure. Not sure if you wanted a pull request (of course, the test
failed), but see #852.

[gracjan]

@khumba: since there is a nice test case now how about you help us fixing this issue? We have something wrong with the definitions of paragraph-separate, paragraph-start or fill-prefix. More documentation here:

http://www.gnu.org/software/emacs/manual/html_node/emacs/Fill-Prefix.html
http://www.gnu.org/software/emacs/manual/html_node/emacs/Paragraphs.html

[khumba]

I'll take a look when I get a minute. One observation, -- ^ doesn't trigger the problem.

[khumba]

`a3173e9d` is where the problem starts (pull #387).

[khumba]

Okay, I think the problem is that paragraph-separate should only match lines between paragraphs, and not the first line in each paragraph as well. When I remove the " *-- |" case from paragraph-separate, my
test case is fixed. Does this sound sensible?
I'll test this more thoroughly and send another PR. " *-- ^" also needs to be added to paragraph-start.

[khumba]

I have no idea why Github decided that there is quoted text in my previous comment, but it's not... On the subject of parsing bugs :).

[ivan-m]

I normally only see that quoted text in GitHub issues when someone replies via email rather than using the web interface.

[khumba]

"I normally only see that quoted text in GitHub issues when someone replies via email rather than using the web interface."

But then, there's usually text quoted with a greater than symbol or the like, but there wasn't in the email I sent. Guessing it had something to do with the " *-- ^"...

...and not the second paragraph...

[gracjan]

Please have a look at font-lock. There are four symbols that can start haddock comment.

[gracjan]

The precise definition of a paragraph boundary is controlled by the variables paragraph-separate and paragraph-start. The value of paragraph-start is a regular expression that should match lines that either start or separate paragraphs (see Regexps). The value of paragraph-separate is another regular expression that should match lines that separate paragraphs without being part of any paragraph (for example, blank lines). Lines that start a new paragraph and are contained in it must match only paragraph-start, not paragraph-separate. For example, in Fundamental mode, paragraph-start is "\f|[ \t]$", and paragraph-separate is "[ \t\f]$".

[gracjan]

Fixed by #1037.