Fix the Float Serializer with Infinite and NaN Number Values

[JeanArhancet]

Currently, when we receive a float('inf'), the serializer respects the RFC standard and transforms it into a null value.

However, python returns '-Infinity' , 'Infinity' and 'NaN' if allow_nan is true : https://docs.python.org/3.8/library/json.html#infinite-and-nan-number-values

Selected Assignee: @samuelcolvin

[davidhewitt]

Related pydantic/pydantic#7007

Python will also accept -Infinity, Infinity and NaN in JSON inputs by default:

>>> json.loads("[-Infinity, Infinity, NaN]")
[-inf, inf, nan]

[JeanArhancet]

I'd like to tackle this task 😄

@davidhewitt Do I need to implement a Serializer https://serde.rs/impl-serializer.html? because we have to return Infinity...etc without quotes

[davidhewitt]

I think so, and maybe a Deserializer too. I don't know if we can wrap serde_json's implementations or we have to be completely custom.

@samuelcolvin has been considering a JSON parser that works independent of serde specialized for our use case, to enable better error messages and also higher performance. It may be more fruitful to collaborate on that effort rather than spend a lot of time wrapping serde's Deserializer.

I don't think we have any plans to replace serde for serialization, so wrapping/implementing our own Serializer is likely to stick around as a long-term implementation.