Subject: Re: bug#59693: 29.0.50; treesitter in base buffer doesn't respond to modifications in indirect buffer correctly

From: Yuan Fu <[email-masked]>
Date: Sat, 3 Dec 2022 23:20:59 -0800

> On Dec 2, 2022, at 5:01 PM, Yuan Fu <[email-masked]> wrote:
> 
> 
> 
>> On Dec 2, 2022, at 12:33 AM, Eli Zaretskii <[email-masked]> wrote:
>> 
>>> From: Yuan Fu <[email-masked]>
>>> Date: Thu, 1 Dec 2022 21:05:43 -0800
>>> Cc: [email-masked],
>>> [email-masked]
>>> 
>>>> In the insdel.c hooks where you record changes to buffer text, you should
>>>> see if the buffer has a base_buffer, and if so, update any parsers of the
>>>> base buffer as well.
>>> 
>>> Actually there’s a little bit of problem. When we edit the base buffer, we would want to update the parsers in all of its indirect buffers as well, and AFAICT there is no pointer from base buffer to the indirect buffer, only the other way around. 
>> 
>> That's not the problem presented by the OP, though.
> 
> Yeah, but they are the same problem in spirit, ie, parser not updated when base/indirect buffer receive changes.
> 
>> 
>>> We don’t want indirect buffer and base buffers to share parsers, since they can have different narrowing, and semantically indirect buffers should share anything but the text with the base buffer.
>> 
>> Yes, the parsers should not be shared.
>> 
>>> How about this: we change current_buffer->parser_list from a plain list of parsers to a cons (PARSER-LIST . INDIRECT-PARSER-LIST), where PARSER-LIST is as before. But for base buffers, INDIRECT-PARSER-LIST includes all the parsers of its indirect buffers; and for indirect buffers, INDIRECT-PARSER-LIST is nil.
>> 
>> You can maybe have the indirect buffers in the list, not their parsers.
>> That could make it easier to access other treesit-related information of the
>> indirect buffers, if needed.
> 
> Good idea, it’s easier to know when to remove the reference with buffers, aka when buffer is killed.

I now have a patch that fixes this problem. WDYT? I added a new buffer field since it’s cleaner than turning ts_parser_list into a cons, hopefully that’s not frowned upon. 

Yuan