bug#60880: 30.0.50; tree-sitter `treesit-explore-mode' is buggy and does not behave properly

[Mickey Petersen]

Eli Zaretskii <eliz@gnu.org> writes:

>> Cc: 60880@debbugs.gnu.org
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Thu, 19 Jan 2023 14:30:46 -0800
>>
>>
>> Mickey Petersen <mickey@masteringemacs.org> writes:
>>
>> > A medley of issues here:
>> >
>> > 1. Executing `treesit-explore-mode' on a buffer with no valid grammar
>> > support causes the minor mode (and playground buffer) to stick around and 
>> > "load" anyway.
>> >
>> > 2. Bailing out of the grammar prompt does not, in actual fact, stop
>> > explore mode from proceeding. Instead it creates an empty buffer and
>> > it still engages the minor mode.
>> >
>> > 3. Killing the playground buffer does not remove the explore mode buffer.
>> >
>> > 4. treesit-explore-mode is stored against a buffer during
>> > `desktop-save' (and subsequently read with) `desktop-read'. Thus
>> > broken buffers or files inherit the explore mode. This is especially
>> > pernicious due to #1, #2, and #3.
>>
>> Ok, I fixed those problems. Now if the language is not available,
>> treesit-explore-mode raises an error instead of continuing, desktop-save
>> will not save the explorer buffer, and killing the source buffer also
>> kills the explorer buffer.
>
> I don't think the desktop-save part is correct: the test should be at
> desktop-read time, not at desktop-save time.  Because the fact we had
> the language available when we saved the desktop doesn't guarantee we
> will have it available when restoring that desktop: it could be in a
> different build of Emacs or even on a different machine.
>

> I'm not sure I understand the problem which desktop-read has when
> restoring desktop with buffers in treesit-explore-mode, but if the
> problems are more than just warning messages, then desktop-read should
> detect these problems, emit an echo-area message, and refrain from
> restoring the mode.  Like it does with buffers that visited files
> which are no longer there, for example.

Another problem is that it stops the loading process, pending manual
selection of the grammar you want explore mode to use. It would be
nice if we saved the previous choice -- when you made the choice to
begin with -- so that, upon read, it does not have to ask.

That way the desktop read experience is not interrupted by prompts
during Emacs startup.