Exception while getting simple string from Web API

[francotiveron]

Description

Failure when calling a simple string returning GET call

Repro steps

• create a F# web api app with the following controller

[<ApiController>]
type YatpApiController() = 
   inherit ControllerBase()

   [<HttpGet("version")>]
   member __.Get() = "0.0"

• create a F# client console application

module Yatp.Client

open SwaggerProvider
open System.Net.Http
open System

//let [<Literal>] Schema = "swagger.json"
let [<Literal>] Schema = @"http://localhost:5166/swagger/v1/swagger.json"
type YatpClient = OpenApiClientProvider<Schema>
let client = YatpClient.Client(new HttpClient(BaseAddress = Uri(@"http://localhost:5166/")))
let version = client.GetVersion().Result //Error
printfn "%A" version

Schema

{
  "openapi": "3.0.1",
  "info": {
    "title": "Yatp.Api",
    "version": "1.0"
  },
  "paths": {
    "/version": {
      "get": {
        "tags": [
          "YatpApi"
        ],
        "responses": {
          "200": {
            "description": "Success",
            "content": {
              "text/plain": {
                "schema": {
                  "type": "string"
                }
              },
              "application/json": {
                "schema": {
                  "type": "string"
                }
              },
              "text/json": {
                "schema": {
                  "type": "string"
                }
              }
            }
          }
        }
      }
    },

Expected behavior

the value "0.0" should be returned and then printed

Actual behavior

An exception is raised in the client.GetVersion().Result line

One or more errors occurred. (The JSON value could not be converted to System.String. Path: $ | LineNumber: 0 | BytePositionInLine: 3.)

Known workarounds

None

Affected Type Providers

• OpenApiClientProvider

Related information

• Operating system: Windows 10
• .NET Runtime: .NET 6

NOTE: C# client generated with NSwag or Visual Studio works as expected

var yatpClient = new Yatp.Client.YatpClient(@"http://localhost:5166/", new HttpClient());
var version = await yatpClient.VersionAsync(); //OK
Console.WriteLine(version);

[sergey-tihon]

Workaround here will be to modify server to return JSON "0.0" instead of plain text 0.0

It can be done using Produces(MediaTypes.ApplicationJson) attribute

[<ApiController>]
type YatpApiController() = 
   inherit ControllerBase()

   [<HttpGet("version"); Produces(MediaTypes.ApplicationJson)>]
   member __.Get() = "0.0"

another option here is to inherit from provided client and override member Deserialize, basically do nothing with response instead of default behavior JsonSerializer.Deserialize(value, retTy, options)

[sergey-tihon]

Fixed in v2.0.0-beta3 by adding Accept header to requests, forcing server to respond with json.