bug#59686: 30.0.50; tree-sitter indentation in some loops and conditional statements is wrong

[Theodor Thornhill via "Bug reports for GNU Emacs, the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>]

Bruce Stephens <bruce.stephens@isode.com> writes:

> On 02/12/2022 08:39, Eli Zaretskii wrote:
>
>> FWIW, this is an unusual style, so I see no catastrophe if it is not 110%
>> according to expectations.  Users can easily fix that by tweaking their BOLs
>> where important.
>
>
> The example I gave would be unusual, I think, but I'd argue that the 
> situations where I saw the problem are quite natural.
>
> For example,
>
>                  } else if ( MYSTRCMP (attname, SOME_PREFIX_X400ADDRESS) ||
>                              MYSTRCMP (attname, SOME_PREFIX_X400) ) {
>                      FOO_ptr orp = foo_std2foo (val);
>
> or a function declaration with several arguments with types that are 
> rather long.
>
> I agree it's not a critical bug but if there's no appropriate general 
> fix it would be helpful to have some guidance for users to resolve our 
> specific cases.

This is the case I was thinking of.  In the for-loop a grand-parent-bol
on compound_statement rule would match the 'for' keyword, so the
indentation will be correct, but this one will not, IIRC.  I plan to dig
into this some more soon, but motivation left me a little on that issue.
Maybe we could make a preset like:

```
(seq
 (parent-is "compound_statement") parent (parent-is "for_statement") bol)
```

In other words, make other presets execute sequentially, move point,
check again, and if all are true, pick indent offset.  Or allow multiple
captures, like so:

```
(for_statement @offset-anchor
  body: (compound_statement (_) @to-indent))
```

Here the @to-indent capture would get the new indent level based on
treesit-node-start of for_statement.

What do you think, Yuan?

Theo