bug#59662: 29.0.50; [PATCH] Add treesit--indent-defun

[Theodor Thornhill]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Theodor Thornhill <theo@thornhill.no>
>> Cc: dgutov@yandex.ru, monnier@iro.umontreal.ca, larsi@gnus.org,
>>  59662@debbugs.gnu.org, casouri@gmail.org
>> Date: Thu, 08 Dec 2022 09:56:44 +0100
>> 
>> Eli Zaretskii <eliz@gnu.org> writes:
>> 
>> > My point is that tree-sitter in many cases parses the program better
>> > than syntax-ppss.  So if we can use its information about comments and
>> > strings, why not do that?  It's exactly the same logic that Dmitry
>> > used:
>> >
>> 
>> Something like this?  If we add a defvar such as the below, similar to
>> treesit-defun-type-regexp we can use that in the function below:
>> 
>> ```
>> (defvar-local treesit-comment-type-regexp nil
>>   "A regexp that matches the node type of comment nodes.
>> 
>> For example, \"(line|block)_comment\". ")
>
> The intent is that major modes set this variable?  SGTM.

Yeah, that was the idea.

>
>>     (if (or (and (treesit-available-p)
>>                  (treesit-ready-p (treesit-language-at (point)))
>
> I'd imagine that this kind of test should have an API, so the
> treesit-ready-p call should not be made explicitly?  Yuan, WDYT?
>
> Also, isn't it enough to check whether the buffer has a tree-sitter
> parser or something?
>
>> The error handling here is naive, but is this something in the line of
>> what you're suggesting?
>
> Yes, it is what I had in mind, but see above.

What about this?  I changed it to make a point that we should fill if
inside of a string or comment, and indent if inside a code block.  We
one such variable for each type, or in both as suggested below.

```
(defvar-local treesit-text-type-regexp nil
  "A regexp that matches the node type of textual nodes.

For example, \"(line|block)_comment\" in the case of a comment,
or \"string_literal\" in the case of a string.")

(defun prog-reindent-defun (&optional argument)
  "Refill paragraph or reindent the definition that the point is on.

If the point is in a string, or in a comment, or there is a
comment on the current line, fill the paragraph that the point is
in or is on the same line.

Otherwise, reindent the definition around or below point."
  (interactive "P")
  (save-excursion
    (if (or (and (treesit-parser-list)
                 (string-match-p
                  treesit-text-type-regexp
                  (treesit-node-type (treesit-node-at (point)))))
            (nth 8 (syntax-ppss))
            (re-search-forward comment-start-skip (line-end-position) t))
        (if (memq fill-paragraph-function '(t nil))
            (lisp-fill-paragraph argument)
          (funcall fill-paragraph-function argument))
      (end-of-defun)
      (let ((end (point)))
        (beginning-of-defun)
        (indent-region (point) end)))))
```