bug#62333: 30.0.50; Issue with tree-sitter syntax tree during certain changes

[Eli Zaretskii <eliz@gnu.org>]

> Date: Mon, 27 Mar 2023 01:00:20 +0300
> Cc: wkirschbaum@gmail.com, casouri@gmail.com, 62333@debbugs.gnu.org
> From: Dmitry Gutov <dgutov@yandex.ru>
> 
> > So you are suggesting to introduce kludges like font-lock-dont-widen
> > in all of those places?
> 
> font-lock-dont-widen is a kludge, but that's largely determined by the 
> way it's defined and used.

With parser-based features, we have an opportunity to do this in a
cleaner manner.

> If we take indent-for-tab-command, for example, it doesn't have such a 
> variable, and doesn't really need to: the top-level command calls 
> 'widen', and then indent-line-function (set by major mode and altered by 
> e.g. mmm-mode) is free to impose its specific bounds.

I thought about a lower-level, infrastructure-level, mechanism that
could be used to restrict a parser to a certain region of the buffer.
Then this could be used by every feature based on parsers, instead of
us having to invent a separate solution for each one.

> The "grand unified theory of mixed major modes" has been attempted a few 
> times in the past, and never reached anything practical.

But here we have a unique opportunity to maybe find a solution, at
least for stuff based on tree-sitter and similar libraries.  That
maybe not "grand", but certainly "respectable".

> >> Except it's already limited by narrowing.
> > 
> > Which is a fragile, semi-broken means, as we all know.
> 
> What is a broken mess, is user-level narrowing.

Which is why restricting parsers should not be a user-level feature.

> > Look, I'm trying to see how we could come up with an infrastructure
> > that will support multiple modes and other similar features in the
> > same buffer without relying on narrowing, thus bypassing the
> > disadvantages and difficulties that come with narrowing.  I think we
> > have a good chance here to come up with such a solution, specifically
> > for features that us a parsing library.  If you aren't interested in
> > discussing that, and think we should stick to narrowing, then this
> > goes nowhere, and I'd rather bow out of it.
> 
> What I've seen here so far is you suggesting we go ahead and break the 
> existing convention and then let "them" (third-party authors including 
> myself) come up with a new working one.

You are mixing two semi-separate issues: how to fix the immediate
problem with blink-matching-paren (if we consider it a serious
problem), and how to try solving similar issues as a whole.  The
latter is a long-term goal, and we can discuss it freely and calmly;
whereby ideas can be brought up even if they might not be the most
clever ones or the ones with which you personally agree.

> My stance here is we shouldn't break it before we create a new one.

No one broke anything.  We are just discussing ideas.  Please don't
exaggerate.