Implementation of conversion traits for 3rd party types

[birkenfeld]

PyO3 kind of has the same problem as serde: if you wanted to use 3rd-party types in your pyfunctions, the conversion traits (Serialize, FromPyObject) would have to be implemented by the lib that defines them, but usually isn't. In your crate using pyo3, you can then only work with newtype wrappers, which is ok but not great. In particular, it makes using the same functions/methods also from Rust annoying.

I don't really know of a workaround. But I would never have suspected about the one with inventory, used for avoiding specialization, so who knows... 😄

[birkenfeld]

serde's solution: https://serde.rs/remote-derive.html

[davidhewitt]

Interesting alternative which came up in #884 was that perhaps we can add an annotation to method arguments to use a custom converter.