Deserializer throws exception when request body is empty.

[BennieCopeland]

When using the ThothSerializer in Giraffe, attempting to deserialize an empty request body generates an exception from Newtonsoft.Json with Error reading JToken from JsonReader. The default Giraffe serializer (Utf8Json) returns null for the same case.

This happens whether I use ctx.BindJsonAsync, Controller.getJson, or ThothSerializer.ReadBody. For ReadBody, I would prefer this to just be an Error allowing me to return a 403 to the client.

[MangelMaxime]

Hello, in theory, Thoth.Json.Net should capture all the errors coming from Newtonsoft and map them into Error ....

Source:
https://github.com/thoth-org/Thoth.Json.Net/blob/35402a9d8b8b5efd7c61cb1959907a6606fd83f6/src/Decode.fs#L97-L106

Can you please check what is the type of exception you are having?

[BennieCopeland]

Using let! request = ThothSerializer.ReadBody ctx AccountRequest.decode causes:

Giraffe.Middleware.GiraffeErrorHandlerMiddleware[0]
      An unhandled exception has occurred while executing the request.
      Newtonsoft.Json.JsonReaderException: Error reading JToken from JsonReader. Path '', line 0, position 0.
         at Newtonsoft.Json.Linq.JToken.ReadFromAsync(JsonReader reader, JsonLoadSettings settings, CancellationToken cancellationToken)
         at FSharp.Control.Tasks.TaskBuilder.bindTask[a,b](Task`1 task, FSharpFunc`2 continuation)
         at FSharp.Control.Tasks.TaskBuilder.tryFinally[a](FSharpFunc`2 step, FSharpFunc`2 fin)
         at FSharp.Control.Tasks.TaskBuilder.using[a,a](a disp, FSharpFunc`2 body)
         at FSharp.Control.Tasks.TaskBuilder.tryFinally[a](FSharpFunc`2 step, FSharpFunc`2 fin)
         at FSharp.Control.Tasks.TaskBuilder.using[a,a](a disp, FSharpFunc`2 body)
         at FSharp.Control.Tasks.TaskBuilder.run[a](FSharpFunc`2 firstStep)
      --- End of stack trace from previous location ---
         at FSharp.Control.Tasks.TaskBuilder.bindTask[a,b](Task`1 task, FSharpFunc`2 continuation)
         at FSharp.Control.Tasks.TaskBuilder.run[a](FSharpFunc`2 firstStep)
      --- End of stack trace from previous location ---
         at FSharp.Control.Tasks.TaskBuilder.bindTaskConfigureFalse[a,b](Task`1 task, FSharpFunc`2 continuation)
         at Api.Session.Controller.postAction@69.Invoke(Unit unitVar) in C:\Development\IdentityManager\src\TSC.IdentityManager.Server\Api\SessionController.fs:line 69
         at FSharp.Control.Tasks.TaskBuilder.run[a](FSharpFunc`2 firstStep)
      --- End of stack trace from previous location ---
         at FSharp.Control.Tasks.TaskBuilder.bindTaskConfigureFalse[a,b](Task`1 task, FSharpFunc`2 continuation)
         at FSharp.Control.Tasks.TaskBuilder.run[a](FSharpFunc`2 firstStep)
      --- End of stack trace from previous location ---
         at FSharp.Control.Tasks.TaskBuilder.bindTaskConfigureFalse[a,b](Task`1 task, FSharpFunc`2 continuation)
         at FSharp.Control.Tasks.TaskBuilder.run[a](FSharpFunc`2 firstStep)
      --- End of stack trace from previous location ---
         at FSharp.Control.Tasks.TaskBuilder.bindTaskConfigureFalse[a,b](Task`1 task, FSharpFunc`2 continuation)
         at FSharp.Control.Tasks.TaskBuilder.run[a](FSharpFunc`2 firstStep)
      --- End of stack trace from previous location ---
         at FSharp.Control.Tasks.TaskBuilder.bindTaskConfigureFalse[a,b](Task`1 task, FSharpFunc`2 continuation)
         at FSharp.Control.Tasks.TaskBuilder.run[a](FSharpFunc`2 firstStep)
      --- End of stack trace from previous location ---
         at FSharp.Control.Tasks.TaskBuilder.bindTaskConfigureFalse[a,b](Task`1 task, FSharpFunc`2 continuation)
         at FSharp.Control.Tasks.TaskBuilder.run[a](FSharpFunc`2 firstStep)
      --- End of stack trace from previous location ---
         at FSharp.Control.Tasks.TaskBuilder.bindTaskConfigureFalse[a,b](Task`1 task, FSharpFunc`2 continuation)
         at FSharp.Control.Tasks.TaskBuilder.run[a](FSharpFunc`2 firstStep)
      --- End of stack trace from previous location ---
         at FSharp.Control.Tasks.TaskBuilder.bindTaskConfigureFalse[a,b](Task`1 task, FSharpFunc`2 continuation)
         at FSharp.Control.Tasks.TaskBuilder.run[a](FSharpFunc`2 firstStep)
      --- End of stack trace from previous location ---
         at FSharp.Control.Tasks.TaskBuilder.bindTaskConfigureFalse[a,b](Task`1 task, FSharpFunc`2 continuation)
         at FSharp.Control.Tasks.TaskBuilder.run[a](FSharpFunc`2 firstStep)
      --- End of stack trace from previous location ---
         at FSharp.Control.Tasks.TaskBuilder.bindTaskConfigureFalse[a,b](Task`1 task, FSharpFunc`2 continuation)
         at FSharp.Control.Tasks.TaskBuilder.run[a](FSharpFunc`2 firstStep)
      --- End of stack trace from previous location ---
         at FSharp.Control.Tasks.TaskBuilder.bindTaskConfigureFalse[a,b](Task`1 task, FSharpFunc`2 continuation)
         at FSharp.Control.Tasks.TaskBuilder.run[a](FSharpFunc`2 firstStep)
      --- End of stack trace from previous location ---
         at IdentityServer4.Hosting.IdentityServerMiddleware.Invoke(HttpContext context, IEndpointRouter router, IUserSession session, IEventService events, IBackChannelLogoutService backChannelLogoutService)
         at IdentityServer4.Hosting.MutualTlsEndpointMiddleware.Invoke(HttpContext context, IAuthenticationSchemeProvider schemes)
         at Microsoft.AspNetCore.Authentication.AuthenticationMiddleware.Invoke(HttpContext context)
         at IdentityServer4.Hosting.BaseUrlMiddleware.Invoke(HttpContext context)
         at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
         at Microsoft.AspNetCore.Session.SessionMiddleware.Invoke(HttpContext context)
         at Giraffe.Middleware.Invoke@63-5.Invoke(Unit unitVar)
         at FSharp.Control.Tasks.TaskBuilder.tryWith[a](FSharpFunc`2 step, FSharpFunc`2 catch)

[BennieCopeland]

The code you linked looks like it is from the string decoder and is wrapped in a try catch, but the call in ThothSerializer is not wrapped in a try catch.

Thoth.Json.Giraffe/src/ThothSerializer.fs

Lines 56 to 68 in 4a18b7e

	static member ReadBodyRaw (ctx: HttpContext) =
	task {
	use stream = new System.IO.StreamReader(ctx.Request.Body, Utf8EncodingWithoutBom, true, DefaultBufferSize, true)
	use jsonReader = new JsonTextReader(stream)
	let! json = JValue.ReadFromAsync jsonReader
	return json
	}
	static member ReadBody (ctx: HttpContext) (decoder: Decoder<'T>) =
	task {
	let! json = ThothSerializer.ReadBodyRaw ctx
	return Decode.fromValue "$" decoder json
	}

[MangelMaxime]

Hum, you are right it is using Decode.fromValue I tought it was Decode.fromString.

I guess we are using Decode.fromValue here because we want to use a StreamReader instead of JsonTextReader. Probably for performance or something like that.

We should definitely port the try-catch from Decode.fromString here.

[BennieCopeland]

I forked it to take a look. Did you know the solution file (.sln) is missing?

[MangelMaxime]

@BennieCopeland I just released a new version 4.3.0 with your changes in it.

I forked it to take a look. Did you know the solution file (.sln) is missing?

I don't remember if Visual Studio requires it but Ionide, Rider, dotnet cli can work without it. As you can open a folder instead of a solution.

I find sln files not really useful in general because it hides files from you or you have to add all your files to it. Where the file system already does that (kind of).

Also, I am not really a .NET user more of a Fable user where sln are not needed either so I can be wrong.