Serializing int64 inside discriminated unions generates irreversable JSON representation

Description

Serializing int64 inside discriminated unions generates incompatible JSON, in other words, the generated JSON cannot be deserialized back to original type.

After tracking down the issue at Fable.Remoting, I narrowed it down to the following code that doesn’t work:

open Fable.Core
open Fable.Core.JsInterop

type SingleCase  = SingleCase of int64

let input = SingleCase 20L
printfn "%A" (ofJson<SingleCase> (toJson input))

You will get the error:

Uncaught Error: Cannot deserialize into Test.SingleCase - Error (inflate): Input string was not in a correct format. - Data: '{"SingleCase":{"low":20,"high":0,"unsigned":false}}'

Note: the same issue happens even with unions of multiple cases.

The Fable JsonConverter on the server is also unable to deserialize the date {"low":20,"high":0,"unsigned":false} into a proper int64 and throws this exception:

System.Exception: Expecting int64 but got StartObject.
/*
rest of irrelevant stack strace
*/ 

where the StartObject indicates that the deserializer encountered an object literal where it was expecting int64

Related information

• Fable version (dotnet fable --version): 1.3.17 && repl
• Operating system: Windows 10 && linux on Travis CI

[MangelMaxime]

Thank you 😃

I think it will not pass the test suite yet. I need to had more primitive type like Dates for example 😃

[Zaid-Ajaj]

@MangelMaxime I took a closer look, very interesting way for deserialization, I wonder if it can handle the exhaustive test suite of Fable.Remoting, I will try it soon and otherwise I will be swarming you with issues 😂 😜