Re: treesit indentation "blinking"

[Dmitry Gutov]

On 03/04/2023 12:59, Alan Mackenzie wrote:
> Hello, Dmitry.
>
> On Mon, Apr 03, 2023 at 00:21:18 +0300, Dmitry Gutov wrote:
> > On 02/04/2023 20:23, João Távora wrote:
> > > So my initial idea was to tone down electric-indent-chars, at least
> > > for the moment.  And Dmitry's idea was to make electric-indent-chars
> > > be ambitious_only_  if electric-pair-mode is enabled (by the user).
> > > Maybe we should bring back that idea, and it seems the least bad of the
> > > bunch right now.
>
> > Alternatively, we only perform "electric indent" (aside from after RET)
> > when the parse tree does not contain errors.
>
> That is NOT electric indentation.  The whole point about electric
> indentation is for it to take effect whilst point is still on the line
> being edited.  Thus, for example, you can see whether or not the line
> needs breaking, or whether there's room for a short comment at the end
> of the line.

Wouldn't you know whether the line needs breaking, as long as the line 
was indented correctly when you opened it with RET?

> What you're proposing is something which would almost never trigger,
> since a line being edited will not have a parse tree without errors (if
> I've understood that properly).  If it did trigger at some point, that
> would likely cause annoyance and puzzlement.

That's a fair assessment, but it's going to trigger in a lot of cases 
still: after ;, or after a paren or brace being closed.

This is not a substitute for enabling electric-pair-mode, alas. Just a 
less hackish way to check the same thing rather than check for this 
particular mode being enabled.

I would also prefer c++-ts-mode supported indentation with closing 
braces missing, but we're really limited by what the parser provides. 
E.g. for this code

  int foo() {
    for (;;) {

we get this parse tree:

  (ERROR (primitive_type)
   (function_declarator declarator: (identifier)
    parameters: (parameter_list ( )))
    { for ( ; ; ) {)

where the "for" statement isn't even present (the separate tokens are 
parsed as leaf nodes, and that's it). It's difficult to write meaningful 
indentation rules that would match this.