Specify name of #[pyclass] dynamically in macro

[rcrisanti]

I'm attempting to use a macro (with the help of paste) to make a class inheritance hierarchy less verbose. What I would ideally like to do is something like this:

use paste::paste;
use pyo3::prelude::*;

macro_rules! class_hierarchy {
    ($parent:ident: $($child:ident),*) => {
        paste! {
            #[pyclass(subclass, name=stringify!($parent))]
            pub struct [<Py $parent>];

            $(
                #[pyclass(extends=[<Py $parent>], name=stringify!($child))]
                pub struct [<Py $child>];
            )*
        }
    };
}

class_hierarchy!(Parent: Child1, Child2);

Where in this case I would end up with structs named PyParent, PyChild1, & PyChild2, but which correspond to python classes just named Parent, Child1, and Child2, respectively. But this errors because of the stringify! usage with "expected string literal".

Is there some way to accomplish what I'm trying to do here? Or is there no way to get around the fact that the #[pyclass(name)] must be a literal

[davidhewitt]

I think it needed to be a literal in the past due to limitations about creating c-strings at compile time. Potentially it would be ok to relax this to any expression which can evaluate at const-time to a c-str. I would be happy to review a PR which experiments with changing the name attribute to accept either a string literal OR an expression which evaluates to &'static CStr. I think we'd soon learn if that's actually feasible.