Add error for undefined function in shader

[MoltenCoffee]

Problem
Currently, as described in #72120, when an undefined function is called in a shader, an error is shown for the number of arguments, as the for-loop looking for functions did not find any but does following code to continue.

Solution
Adds an error when an undefined function is called in a shader, when the loop does not find the matching function.
Fixes #72120

[MoltenCoffee]

I just noticed a similar but different warning elsewhere:

_set_error(vformat(RTR("No matching function found for: '%s'."), String(funcname->name)));

This one should actually fire if we return false. An option would be to return false instead of setting an error, as that would trigger behavior that is already defined, but not visbily triggered at the moment.

[bitsawer]

Indeed, there are a few places that call _validate_function_call() and set the error message differently if it returns false. The logic seems good otherwise, I would maybe keep the exists boolean and simply change the last check to something like this (not tested):

if (exists) {
    if (last_arg_count > args.size()) {
        _set_error(vformat(RTR("Too few arguments for \"%s(%s)\" call. Expected at least %d but received %d."), String(name), arg_list, last_arg_count, args.size()));
    } else if (last_arg_count < args.size()) {
        _set_error(vformat(RTR("Too many arguments for \"%s(%s)\" call. Expected at most %d but received %d."), String(name), arg_list, last_arg_count, args.size()));
    }
}

[MoltenCoffee]

That seems like a better solution indeed! Seems to work alright.

[bitsawer]

You need to fix the code formatting to pass tests, we use clang-format: https://docs.godotengine.org/en/latest/contributing/development/code_style_guidelines.html#using-clang-format-locally (in this case you might be able to fix the style by hand, but using the tool is more reliable).

Also, please squash your commits into a single commit, see https://docs.godotengine.org/en/latest/contributing/workflow/pr_workflow.html#the-interactive-rebase

[bitsawer]

Tested locally and it works, looks good to me.

[YuriSizov]

So if I understand correctly, we aren't actually adding a new error message, we already have one. And with this PR we are preventing earlier checks from triggering and showing a less useful message, right?

[MoltenCoffee]

So if I understand correctly, we aren't actually adding a new error message, we already have one. And with this PR we are preventing earlier checks from triggering and showing a less useful message, right?

Correct. The PR was created under a different assumption and although it has been updated since, the title hasn't.

[YuriSizov]

Thanks! And congrats on your first merged Godot pull request!