Rust enum support

[angelorodem]

Hi, i could not find the reason on gh issues or in other places,
what is the current limitation that prevents an implementation that is able to Serialize/Deserialize rust non C-like enums?
is that some limitation because it is not possible in no_std or is just a missing feature?

[ryan-summers]

I had one question when reading this: How does a complex rust enum map into json object representations?

• Seems like this is possible without alloc, so we could likely follow what serde-json does (see https://github.com/serde-rs/json/blob/master/tests/test.rs#L496)

After researching serde-json, it seems to me like this is simply missing implementation. If you'd like to take it on, I'd be happy to review the change!

[zeenix]

Seems like this is possible without alloc, so we could likely follow what serde-json does (see https://github.com/serde-rs/json/blob/master/tests/test.rs#L496)

Perhaps that's true for JSON de/ser but serde itself only supports externally-tagged enums representation without alloc. This will greatly limit any enum support in this crate, I'm afraid. 😞

While serde_json already supports alloc, its serialisation API requires std and hence it's not very useful. The maintainer of serde_json has also explicitly turned the down possibility of making the ser API work for no_std.

This means that folks who can't do std but are fine with alloc, and need complex enums and/or a generic Value type, can use neither this crate nor serde_json. 😔

So, I wonder if the maintainers would consider adding an optional alloc feature?

[zeenix]

While serde_json already supports alloc, its serialisation API requires std and hence it's not very useful. The maintainer of serde_json has also explicitly turned the down possibility of making the ser API work for no_std.

This means that folks who can't do std but are fine with alloc, and need complex enums and/or a generic Value type, can use neither this crate nor serde_json. 😔

Thinking more about this, there is nothing stopping folks from enabling alloc in serde while still using this crate (assuming of course complex enum support is added, which is what this issue is about). Having said that, if most people will have to enable alloc in serde to make full use of this feature, not much point in resisting alloc feature to this crate then, if it gives people very useful features like a generic Value type.