bug#31772: 26.1; (thing-at-point 'list) regression

["Andreas Röhler" <andreas.roehler@easy-emacs.de>]

On 11.09.2018 13:16, Eli Zaretskii wrote:
>> From:  Leo Liu <sdl.web@gmail.com>
>> Cc: 31772@debbugs.gnu.org,  tino.calancha@gmail.com
>> Date: Tue, 11 Sep 2018 18:26:36 +0800
>>
>> The difference is on what to return when (up-list -1) fails. They both
>> try to return the sexp at point but the patched behaviour try returning
>> the whole sexp while the one in <= 25.1 cut off the sexp from point.
>>
>> Looking at the code in 25.1 it looks to me the original author had a
>> thinko i.e. he/she meant to write:
>>
>> (if (>= opoint (point))
>>      (cons (point) end))
>>
>> but instead write
>>
>> (if (>= opoint (point))
>>      (cons opoint end))
>>
>> which resulted in some weird cases that you mentioned in previous email.
> 
> Right.
> 
>>> Would it be possible to modify list-at-point so that it keeps the
>>> current behavior, perhaps as an option?  I'd like to find a solution
>>> that doesn't just revert to the old behavior, but allows those who
>>> need the new behavior to have it in some reasonable way.
>>
>> Yes, this can be done. For example:
>>optional ignore-comment-or-string)
>>    "Return the Lisp list at
>> (defun list-at-point (& point, or nil if none is found.
>> If IGNORE-COMMENT-OR-STRING is non-nil comments and strings are
>> treated as white space."
>>    (let ((ppss (and ignore-comment-or-string (syntax-ppss))))
>>      (save-excursion
>>        (goto-char (or (nth 8 ppss) (point)))
>>        (form-at-point 'list 'listp))))
> 
> Would you mind submitting a patch that includes the above, and also
> fixes/augments the tests accordingly?  I think these changes then
> could go into the emacs-26 branch, unless someone raises objections.
> 
> Thanks.
> 
> 
> 



The basic decision to make is to put some section as comment or not.

If code is commented out, it looses its lisp-syntax. It's plain text.
Therefor no lisp-list can exist and no need for a var 
ignore-comment-or-string.