Subject: Re: bug#60197: 30.0.50; beginning-of-defun broken after new treesit impl

From: Theodor Thornhill <[email-masked]>
Date: Wed, 21 Dec 2022 06:58:53 +0100

On 21 December 2022 05:08:09 CET, Yuan Fu <[email-masked]> wrote:
>
>Theodor Thornhill <[email-masked]> writes:
>
>> Hi, Yuan!
>>
>> It seems 'prog-fill-reindent-defun' is broken after the latest changes
>> to treesit-beginning-of-defun.  The culprit is that we now use remap
>> instead of setting the beginning-of-defun-function.  What is the
>> reasoning behind that change?  Can't we just rely on the variable
>> beginning-of-defun-function?
>
>Not really, end-of-defun uses beginning/end-of-defun-function in a way
>that’s incompatible with nested defuns[1]. So if we want to support
>navigation nested defuns reliably we need to remap the commands instead.
>In the future (ie emacs 30), we can extend the current
>beginning/end-of-defun to support nested defuns, then we don’t need to
>remap the commands anymore.
>
>> I see you mentioned it is inteded to be used as a command, but surely
>> both should be possible?
>
>Could you remind me where is this function defined? I should have
>updated it when I changed the defun navigation implementation. (It was
>broken by my change before the defun nav change which you noticed, I
>thought I’m going to fix it with the new defun nav functions, but I
>forgot...)
>
>Yuan
>

It is in prog-mode.el, in the master branch. But the biggest issue now is that every function or command that relies on beginning-of-defun and  end-of-defun is broken. 

>
>[1] For example, a nested defun like this:
>
>def parent:
>    (1)
>    def child:
>        return 0
>(2) return 1
>(3)
>
>When point is at (1), end-of-defun calls beginning-of-defun-function
>followed by end-of-defun-function to check if point is in a defun: if
>point ends up after the starting point, then starting point is inside a
>defun, and we can stop there. In this case, point ends up at
>(3), because b-o-d-f goes to previous b-o-d, which is the beg of parent,
>then e-o-d-f goes to (3), which is the end of that parent, and
>end-of-defun stops at (3).
>
>However, we should have gone to (2), which is the immediately following
>end-of-defun.
>

That depends on the tactic chosen, right?

>Thanks,
>Yuan

Are you sure this isn't compatible?