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

[Yuan Fu]

> On Dec 2, 2022, at 12:33 AM, Eli Zaretskii <eliz@gnu.org> wrote:
> 
>> From: Yuan Fu <casouri@gmail.com>
>> Date: Thu, 1 Dec 2022 21:05:43 -0800
>> Cc: miha@kamnitnik.top,
>> 59693@debbugs.gnu.org
>> 
>>> 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.

Yuan