json.% generates invalid json for NaN, Inf

[timotheecour]

Example

when true: # D20210513T172224:here
  import std/json
  let a = [NaN, Inf, -Inf, 0.0, -0.0, 1e20, 1.5]
  let j = %a
  echo j # prints: `[nan,inf,-inf,0.0,-0.0,1e+20,1.5]`, which is invalid json (eg will fail in js console with `JSON.stringify('[nan,inf,-inf,0.0,-0.0,1e+20,1.5]')`)
  let j2 = $j
  let j3 = j2.parseJson # errors (as it should): Error: unhandled exception: input(1, 4) Error: { expected [JsonParsingError]

Current Output

see comments

Expected Output

produce valid json

Possible Solution 1

NaN, Inf,-Inf could use newJRawNumber mechanism we added recently, but this may still lead to an ambiguity when interpreting nan for eg, as this could either mean a string nan or a number nan.

We should at least ensure roundtrip property, so that Inf => "inf" => Inf

Possible Solution 2

cast the Inf/-Inf/NaN to uint first, which would have other benefits (eg preserving bit pattern for nan so that nan value is preserved)

But this should be handled transparently for serialization/deserialization purposes

Additional Information

1.5.1 1e080eb
also affects jsonutils, which reuses json.% for this part
similar to https://perlmaven.com/parsing-nan-in-json (see also https://stackoverflow.com/questions/6601812/sending-nan-in-json)