How does c-ts-mode, tree-sitter indentation, and preprocessor directives work?

["Björn Lindqvist" <bjourne@gmail.com>]

Hello Emacs developers!

I've been trying to get c-ts-mode to indent like I want, but I'm
running into problems related to preprocessor directives. For
example, consider a type definition nested in two #ifdefs:

    #ifdef X
    #ifdef Y
    typedef int foo;
    #endif
    #endif

Since both the parent and grand parent of the type_definition is a
preproc_ifdef no rule matches. Another issue is that I want my
preprocessor directives kept at column 0, which unfortunately screws
up all rules that refer to the parent. E.g.:

    ((parent-is "if_statement") standalone-parent 4)

Doesn't work for

    int main() {
        if (true)
    #ifdef A
            prutt();
    #else
            fis();
    #endif
    }

The rule I'd like to express is "take the indent of the closest
*indenting* parent and add one indent". That rule would match whether
that parent is a "while_statement", "if_statement", "for_statement",
etc. You can't express such rules with tree-sitter, can you?

Btw, I get that tree-sitter can't handle *all* weird preprocessor
constructs you can create, but my examples are really common and
appear in most C code bases.


-- 
mvh/best regards Björn Lindqvist