[BUG] org-complex-heading-regexp should consider COMMENT keywords [9.5.2 (release_9.5.2-25-gaf6f12 @ /home/ignacio/repos/emacs/lisp/org/)]

[Ignacio Casso]

This topic was brought up again in
https://lists.gnu.org/archive/html/emacs-orgmode/2022-05/msg00058.html,
I continue the discussion here:

>> Still, I think it might be interesting to compare this topic with the
>> one I linked in my reply,
>> https://lists.gnu.org/archive/html/emacs-orgmode/2022-03/msg00293.html,
>> which it's basically the same bug report but about COMMENT keywords. In
>> that regard, I have tested that org-capture targets do work regardless
>> of statistcs cookies. Could not something equivalent be done so that
>> they also work regardless of COMMENT keywords? Feel free to reply in
>> that other thread if you feel this is off-topic here.
>
>> This bug is related with the issue I reported in
>> https://lists.gnu.org/archive/html/emacs-orgmode/2022-03/msg00293.html. The
>> problem is that `org-heading-components' uses
>> `org-complex-heading-regexp', which does not consider statistics
>> cookies, and neither COMMENT keywords as I reported. I think it should be
>> updated to consider both.
>
> Note that org-complex-heading-regexp-format does consider statistics
> cookies, but only at the beginning/end of the headline title.
> Unfortunately, it is impossible to provide generic printf format to
> match a headline title with arbitrary statistics cookies inserted in the
> middle of it.
>

Could not something equivalent be done for COMMENT keywords and
optionally match them at the beginning of the headline in
`org-complex-heading-regexp-format'? Something like this:

  (setq org-complex-heading-regexp-format
        (concat "^\\(\\*+\\)"
              "\\(?: +" org-todo-regexp "\\)?"
              "\\(?: +\\(\\[#.\\]\\)\\)?"
              "\\(?: +"
+             ;; Headline might be commented
+             "\\(COMMENT \\)?
              ;; Stats cookies can be stuck to body.
              "\\(?:\\[[0-9%%/]+\\] *\\)*"
              "\\(%s\\)"
              "\\(?: *\\[[0-9%%/]+\\]\\)*"
              "\\)"
              "\\(?:[ \t]+\\(:[[:alnum:]_@#%%:]+:\\)\\)?"
              "[ \t]*$"))

This would fix the problem I really cared about: being able to use a
headline as capture target regardless of whether it is commented or
not. Getting the headline text was never important to me, so I don't
really care that much about `org-complex-heading-regexp'.

> As for your other report, it is a hard one - org-complex-heading-regexp
> is hard to modify because we guarantee certain match groups and its hard
> to fit COMMENT in there without breaking backward-compatibility.
>
> I generally dislike the idea of the available plethora of analytic
> regexps with numbered match groups.

Do you mean that there is no way to specify an optional string in a
regular expression without wrapping it in a parenthesized group, which
would break the match group numbering backwards compatibility? I'm not
that familiar with regular expressions, but if that's the case I
completely agree with your last statement.

--Ignacio