Implement Serialize/Deserialize for std::io::Error

[Ekleog]

Hello!

I'm doing a rust program with webassembly “plugins” (a SMTP server, the code is available here). While doing so, there are -> std::io::Result<T> functions that I'd like to implement in webassembly, that may end up calling back into rust to perform IO.

However, in order to do that (be it “expose a -> std::io::Result<T> callback to wasm” or “expose a -> std::io::Result<T> callback from wasm”), I need to have a way to pass an std::io::Error to/from wasm, which basically means serialization (I currently use bincode semi-manually, though hopefully someday wasm-bindgen will support this use case directly).

Currently, what I do is pass a Result<T, String> and then rebuild with std::io::ErrorKind::Other, because I'd rather avoid having lines and lines of serialization boilerplate.

However, I'm thinking it may make sense to have serde already have implementations for std::io::Error as a (std::io::ErrorKind, String)? This is not a perfect identity (because it loses the potential for having raw os errors), but I'm thinking it should hopefully be good enough?

Related to #1480, though I think being able to (de)serialize std::io::Result is a lot less use-case-specific than just std::io::ErrorKind (although I'd guess it'd also solve that other use case as I suppose the implementation will most likely go through serializing ErrorKind)

Anyway, thank you for this awesome crate :)

[dtolnay]

I'd prefer not to build this into the serde crate. But it would be possible for another crate to provide serialization/deserialization logic for std::io::Result that's usable through serde's serialize_with and deserialize_with attributes.

[Ekleog]

I understand! FWIW, I built https://crates.io/crates/serde-error in the meantime. To the best of my knowledge it is bug-free, feature-complete and not only used by me (though the download count makes me guess it's not highly used). So feel free to link to it should other people request it! :)

Thank you for serde anyway, it's great! :D