Awkward pybind signatures

[Helveg]

Describe the bug
arbor.mechanism's set of accepted arguments are a bit awkward because the signature with positional arguments has anonymous parameter names. It binds arg0 instead of name:

TypeError: __init__(): incompatible constructor arguments. The following argument types are supported:
    1. arbor._arbor.mechanism(arg0: str)
    2. arbor._arbor.mechanism(name: str, params: Dict[str, float])

I suppose this occurs for all functions with similar signatures?

Shouldn't the signatures be:

1. arbor._arbor.mechanism(name: str)
2. arbor._arbor.mechanism(name: str, params: Dict[str, float])

I can do arbor.mechanism("name", {}) and arbor.mechanism(name="name", params={}) and arbor.mechanism("name") but not arbor.mechanism(name="name")

[brenthuisman]

Afaik this is an effect of Pybind. The issue on this is still open: pybind/pybind11#2619

[Helveg]

That issue seems to be about the docstring generation. I can't find where it mentions which arg/kwarg overloads are actually accepted by pybind.

[brenthuisman]

I understood that the docstring generation is a reflection of the way Pybind implements function overloads, it which case it always generates a func(*args, **kwargs) -> Any before the overloads and their signatures.

But I see now that you're asking why arg0 is named arg0, which is nowhere to be seen in https://github.com/arbor-sim/arbor/blob/master/python/mechanism.cpp#L204
Good question. Let me try something, I'll get back to this.