Be explicit that the returned object should be JSON

[dbrattli]

Got a bug in a private repo that took me forever to debug down through Thoth not wanting to run the extra encoders/decoders given to the ThothSerializer. The error I got was:

09:24:47 [Error] () Connection id ""0HLMNEG9T1D5V"", Request id ""0HLMNEG9T1D5V:00000001"": An unhandled exception was thrown by the application.
System.AggregateException: One or more errors occurred. (Could not determine JSON object type for type Shared.Model+Msg+HomeMsg.) ---> System.ArgumentException: Could not determine JSON object type for type Shared.Model+Msg+HomeMsg.
   at Newtonsoft.Json.Linq.JValue.GetValueType(Nullable`1 current, Object value)
   at Thoth.Json.Net.Encode.autoEncoder@454-14.Invoke(Object v)
   at Thoth.Json.Giraffe.ThothSerializer.Giraffe-Serialization-Json-IJsonSerializer-SerializeToBytes[T](T o)
   at Giraffe.ResponseWriters.HttpContext.WriteJsonAsync[T](HttpContext this, T dataObj) in C:\projects\giraffe\src\Giraffe\ResponseWriters.fs:line 137
   at Server.webApp@72-10.Invoke(FSharpOption`1 _arg2) in /Users/dbrattli/Developer/GitHub/xyz/src/Server/Server.fs:line 74
   at FSharp.Control.Tasks.TaskBuilder.StepStateMachine`1.nextAwaitable() in C:\Users\humbo\source\repos\TaskBuilder.fs\TaskBuilder.fs:line 38

The fix was to be explicit and use the json function e.g:

return! Successful.ok (json msg) next ctx

instead of the current:

return! Successful.OK msg next ctx

I propose this fix so that other developers that start off with the SAFE template will not get the same error when they extend their app with more complex types that eventually will make the handler fail with the bug above. The Saturn template btw already uses the json function for returning the object, so this fix should make the Giraffe and Saturn templates equivalent with regards to JSON handling.

[theimowski]

/cc @isaacabraham is that the same change you made a while ago for Saturn?

[dbrattli]

I guess it's OK to simplify this to:

return! json counter next ctx

Should I update the PR?

[isaacabraham]

@theimowski yes that sounds familiar - we should use json and not ok - json counter next ctx should be all we need.

[theimowski]

Thanks! released in 1.5.1