How to contribute genericSeq implementation?

[njlr]

Hello!

I think I have figured out how to implement an Auto decoder for seq<'t>:

    open System
    open System.Collections
    open System.Collections.Generic

    type private UnboxedSeq<'t> (inner : obj seq) =
        interface seq<'t> with
          member this.GetEnumerator() : IEnumerator<'t> =
            (seq {
              for x in inner do
                yield x :?> 't
            }).GetEnumerator()

          member this.GetEnumerator() =
            (this :> seq<'t>).GetEnumerator() :> IEnumerator

    let private genericSeq (elementT : Type) (decoder: BoxedDecoder) =
        let unboxedSeqT = typedefof<UnboxedSeq<_>>
        let seqT = unboxedSeqT.MakeGenericType(elementT)

        fun (path : string) (value: JsonValue) ->
            if not (Helpers.isArray value) then
                (path, BadPrimitive ("a seq", value)) |> Error
            else
                let values = value.Value<JArray>()
                (values, Ok []) ||> Seq.foldBack (fun value acc ->
                    match acc with
                    | Error _ -> acc
                    | Ok acc ->
                        match decoder.Decode(path, value) with
                        | Error er -> Error er
                        | Ok result -> result :: acc |> Ok)
                |> Result.map (fun xs -> Activator.CreateInstance(seqT, xs))

However, I'm not sure how to contribute it.

Should I add tests to this repo first?

[MangelMaxime]

Hello,

Yes the tests are hosted on Thoth.Json repository to make sure that both libraries support the same API.

If you need to test locally the test from your fork, you need to publish the forked version of Thoth.Json on github and then update paket.dependencies file to use your fork.

Thoth.Json.Net/paket.dependencies

Lines 11 to 17 in 6c375e1

	group tests
	# Get the tests from Thoth.Json repo so both project are in sync
	github thoth-org/Thoth.Json:main tests/Types.fs
	github thoth-org/Thoth.Json:main tests/Decoders.fs
	github thoth-org/Thoth.Json:main tests/Encoders.fs
	github thoth-org/Thoth.Json:main tests/ExtraCoders.fs
	github thoth-org/Thoth.Json:main tests/BackAndForth.fs

Also, the generic seq has already been implemented in an unreleased version of Thoth.Json. That specific version of Thoth.Json will never be released because it was too ambitious and I didn't track correctly all the changes I made in it so I am afraid to break people JSON.

I think, it can be a good idea to have a look at it because I think it follows the same API as the current implementation. Using reflection API is always hard to read especially with the need to use boxed/unboxed type to circle around F# limitation.

Here are the places where to find the unreleased implementation:

1. Place where the auto decoder is registered for the type
2. Actual auto decoder code

Note: The unreleased implementation use heavily compiler directive because the goal was to unify Thoth.Json and Thoth.Json.Net so you need to pick what code you want to pick depending on the target runtime.

[MangelMaxime]

I tried your solution but it seems to be hurting the same wall I had in the past:

Object of type 'Microsoft.FSharp.Collections.FSharpList1[System.Object]' cannot be converted to type 'System.Collections.Generic.IEnumerable1[System.String]'.

[njlr]

thoth-org/Thoth.Json#26