bug#74448: 30.0.92; c-ts-mode outlines only work with GNU or emacs style

[Juri Linkov <juri@linkov.net>]

> Hi, I've been playing with the new treesitter based outline minor mode
> and c-ts-mode.
>
> It seems that `outline-hide-subtree' is only working properly when code
> is formatted with either GNU or emacs style.
>
> To test try it with a function where the function declarator is preceded on the
> same line by either type or storage class and type. It will fold the
> function heading instead of the function body.
>
> Problem seems `c-ts-mode--outline-predicate' only checks for
> function_declarator nodes at the beginning of line (like in GNU coding
> style) but other coding style will start the function line with either
> storage class (e.g. static) or type.
>
> Something like this seems to work a little better:
>
> (defun c-ts-mode--outline-predicate (node)
>   "Match outlines on lines with function names."
>   (or (and (or (equal (treesit-node-type node) "function_declarator")
>                (equal (treesit-node-type node) "storage_class_specifier")
>                (equal (treesit-node-type node) "primitive_type")
>                (equal (treesit-node-type node) "type_identifier"))
>            (equal (treesit-node-type (treesit-node-parent node))
>                   "function_definition"))
>       ;; DEFUNs in Emacs sources.
>       (and c-ts-mode-emacs-sources-support
>            (c-ts-mode--emacs-defun-p node))))
>
> But it kind of breaks GNU style by adding two outlines per function
> definition. Also it seems a bit ugly to enumerate all the node types by
> hand, there probably is a nicer way to detect a line with a
> function_declarator not at bol.
>
> Any better idea?

Could you please send a few of short examples of each style.
This would help to make a better decision.
And later these examples could be added to tests.