Re: treesit indentation "blinking"

[Dmitry Gutov]

On 30/03/2023 13:00, João Távora wrote:
> On Thu, Mar 30, 2023 at 10:36 AM Dmitry Gutov <dgutov@yandex.ru> wrote:
> > On 30/03/2023 12:28, João Távora wrote:
> > > This problematic already counts as "bouncing" to me, for some meaning of
> > > "bouncing". c++-mode doesn't behave like that because indentation is
> > > already where it is supposed to be if you type that sequence of
> > > keystrokes.
> >
> > Okay, if that's what you meant.
> >
> > I think this one (indentation after RET in an incomplete function
> > definition) should be fixed in the indentation rules. The contents of
> > electric-indent-chars won't fix it either way.
>
> This is all down to indentation rules, that's how electric-indent-mode
> decides what to do.  My point is that having electric-indent-chars be
> this ambitious with "broken" indentation rules isn't a good place to
> be.

In this instance, removing chars off electric-indent-chars won't conceal 
the problem: the user can still type RET or press TAB and see unexpected 
indentation where Emacs should have been able to guess the correct one.

> What counts as "broken" indentation is also arguable though. When dealing
> with invalid programs, there is really no "right" or "wrong" indentation.
> See my message https://debbugs.gnu.org/cgi/bugreport.cgi?bug=62412#14 where
> I show cases where c++-ts-mode's answer to indenting an invalid program
> makes more sense than c++-mode's answer.

It's not cut-and-dried indeed, but historically, with the "native" major 
modes we, wittingly or not, have used the principle that code fully 
typed until point is considered "decidable", even if some missing code 
after point makes the it incomplete. Even though, on rare occasions, 
continuing to type might change the indentation again (e.g. for "case 
labels", if the indent style dedents them).

> Whatever the indentation rules, the current bouncing is so jarring
> that it really doesn't encourage people to try switching to
> c++-ts-mode, get used to its set of indentation rules, and then perhaps
> experience its other benefits like, say, performance or simplicity.
>
> At least it didn't for me.  I'm back to c++-mode atm.
>
> In my opinion electric-indent-char should be reduced to the default
> and should be added criteriously as the indentation rules they trigger
> are fixed.

We should probably revisit this after an honest attempt to fix these two 
cases.