bug#60602: 29.0.60; treesit-simple-indent doesn't work for top-level nodes

[Yuan Fu]

Piotr Trojanek <piotr.trojanek@gmail.com> writes:

> This problem can be reproduced with a correctly configured c-ts-mode,
> which fails to indent the first line of a code like this, i.e. with
> extra space at the very beginning of file and cursor positioned at
> "main"):
>
> ===
>    int main (int argc, char *argv[])
> {
>   return 0;
> }
> ===
>
> The intent of c-ts-mode--indent-styles is clearly to indent this line
> to 0th column:
>
> (defun c-ts-mode--indent-styles (mode)
>   ...
>          `(((parent-is "translation_unit") parent-bol 0)
>
> However, when indenting this line treesit-simple-indent is called with
> node=translation_unit and parent=nil. It exits too early and doesn't
> consider any indentation rules:
>
> (defun treesit-simple-indent (node parent bol)
>   "..."
>   (if (null parent)
>       (progn (when treesit--indent-verbose
>                (message "PARENT is nil, not indenting"))
>              (cons nil nil))
>
> Note that other tree-sitter modes have similar indentation rules, e.g.
> ruby-ts-mode.el:
>
>    ;; Slam all top level nodes to the left margin
>    ((parent-is "program") parent 0)
>
> and same for typescript-ts-mode.el:
>
>   ((parent-is "program") parent-bol 0)
>
> Perhaps the early exit from treesit-simple-indent could be removed, so
> the indentation rules can decide how to handle a nil parent.

Now NODE is never the root node, so parent is never nil. I believe this
is the best approach.  And personally I think the rule should be

((parent-is "program") point-min 0)

Yuan