wip: #268

src/SwaggerProvider.DesignTime/v3/OperationCompiler.fs

@@ -73,6 +73,12 @@ type OperationCompiler(schema: OpenApiDocument, defCompiler: DefinitionCompiler,
             | true, mediaTyObj -> Some(mediaTyObj)
             | _ -> None
 
+        let (|TextReturn|_|)(input: string) =
+            if input.StartsWith("text/") then Some(input) else None
+
+        let (|TextMediaType|_|)(content: IDictionary<string, OpenApiMediaType>) =
+            content.Keys |> Seq.tryPick (|TextReturn|_|)
+
         let (|NoMediaType|_|)(content: IDictionary<string, OpenApiMediaType>) =
             if content.Count = 0 then Some() else None
 
@@ -176,6 +182,7 @@ type OperationCompiler(schema: OpenApiDocument, defCompiler: DefinitionCompiler,
                             defCompiler.CompileTy providedMethodName "Response" mediaTy.Schema true
 
                     Some(MediaTypes.ApplicationOctetStream, ty)
+                | TextMediaType mediaTy -> Some(mediaTy, typeof<string>)
                 | _ -> None)
 
         let retMime = retMimeAndTy |> Option.map fst |> Option.defaultValue null
@@ -373,6 +380,17 @@ type OperationCompiler(schema: OpenApiDocument, defCompiler: DefinitionCompiler,
                                 }
                             @>
 
+                        let responseString =
+                            <@
+                                let x = %action
+
+                                task {
+                                    let! response = x
+                                    let! data = response.ReadAsStringAsync()
+                                    return data
+                                }
+                            @>
+
                         let responseUnit =
                             <@
                                 let x = %action
@@ -389,15 +407,21 @@ type OperationCompiler(schema: OpenApiDocument, defCompiler: DefinitionCompiler,
                             match retTy with
                             | None -> responseUnit.Raw
                             | Some t when t = typeof<IO.Stream> -> <@ %responseStream @>.Raw
-                            | Some t -> Expr.Coerce(<@ RuntimeHelpers.taskCast t %responseObj @>, overallReturnType)
+                            | Some t ->
+                                match retMime with
+                                | TextReturn _ -> <@ %responseString @>.Raw
+                                | _ -> Expr.Coerce(<@ RuntimeHelpers.taskCast t %responseObj @>, overallReturnType)
                         else
                             let awaitTask t =
                                 <@ Async.AwaitTask(%t) @>
 
                             match retTy with
                             | None -> (awaitTask responseUnit).Raw
                             | Some t when t = typeof<IO.Stream> -> <@ %(awaitTask responseStream) @>.Raw
-                            | Some t -> Expr.Coerce(<@ RuntimeHelpers.asyncCast t %(awaitTask responseObj) @>, overallReturnType)
+                            | Some t ->
+                                match retMime with
+                                | TextReturn _ -> <@ %(awaitTask responseString) @>.Raw
+                                | _ -> Expr.Coerce(<@ RuntimeHelpers.asyncCast t %(awaitTask responseObj) @>, overallReturnType)
             )
 
         if not <| String.IsNullOrEmpty(operation.Summary) then

src/SwaggerProvider.Runtime/RuntimeHelpers.fs

@@ -18,7 +18,6 @@ module MediaTypes =
     [<Literal>]
     let MultipartFormData = "multipart/form-data"
 
-
 type AsyncExtensions() =
     static member cast<'t> asyncOp =
         async {

tests/SwaggerProvider.ProviderTests/SwaggerProvider.ProviderTests.fsproj

@@ -26,6 +26,7 @@
     <Compile Include="v3\Swagger.I0181.Tests.fs" />
     <Compile Include="v3\Swagger.I0219.Tests.fs" />
     <Compile Include="v3\Swashbuckle.ReturnControllers.Tests.fs" />
+    <Compile Include="v3\Swashbuckle.ReturnTextControllers.Tests.fs" />
     <Compile Include="v3\Swashbuckle.UpdateControllers.Tests.fs" />
     <Compile Include="v3\Swashbuckle.ResourceControllers.Tests.fs" />
     <Compile Include="v3\Swashbuckle.FileController.Tests.fs" />

tests/SwaggerProvider.ProviderTests/v3/Swashbuckle.ReturnTextControllers.Tests.fs

@@ -0,0 +1,23 @@
+module Swashbuckle.v3.ReturnTextControllersTests
+
+open Xunit
+open FsUnitTyped
+open SwaggerProvider
+open System
+open System.Net.Http
+
+open Swashbuckle.v3.ReturnControllersTests
+
+let asyncEqual expected actualTask =
+    task {
+        let! actual = actualTask
+        actual |> shouldEqual expected
+    }
+
+[<Fact>]
+let ``Return text/plain GET Test``() =
+    api.GetApiReturnPlain() |> asyncEqual "Hello world"
+
+[<Fact>]
+let ``Return text/csv GET Test``() =
+    api.GetApiReturnCsv() |> asyncEqual "Hello,world"

tests/Swashbuckle.WebApi.Server/Controllers/ReturnTextControllers.fs

@@ -0,0 +1,40 @@
+namespace Swashbuckle.WebApi.Server.Controllers
+
+open System.Text
+open Microsoft.AspNetCore.Mvc
+open Microsoft.AspNetCore.Mvc.Formatters
+open Swagger.Internal
+
+[<Route("api/[controller]")>]
+[<ApiController>]
+type ReturnPlainController() =
+    [<HttpGet; Consumes(MediaTypes.ApplicationJson); Produces("text/plain")>]
+    member this.Get() =
+        "Hello world" |> ActionResult<string>
+
+[<Route("api/[controller]")>]
+[<ApiController>]
+type ReturnCsvController() =
+    [<HttpGet; Consumes(MediaTypes.ApplicationJson); Produces("text/csv")>]
+    member this.Get() =
+        "Hello,world" |> ActionResult<string>
+
+// Simple CSV output formatter
+// This formatter assumes the controller returns a string (already CSV-formatted)
+type CsvOutputFormatter() as this =
+    inherit TextOutputFormatter()
+
+    do
+        this.SupportedMediaTypes.Add("text/csv")
+        this.SupportedEncodings.Add(Encoding.UTF8)
+        this.SupportedEncodings.Add(Encoding.Unicode)
+
+    override _.CanWriteType(t) =
+        // Accept string type only (for simplicity)
+        t = typeof<string>
+
+    override _.WriteResponseBodyAsync(context, encoding) =
+        let response = context.HttpContext.Response
+        let value = context.Object :?> string
+        let bytes = encoding.GetBytes(value)
+        response.Body.WriteAsync(bytes, 0, bytes.Length)

tests/Swashbuckle.WebApi.Server/Startup.fs

@@ -24,6 +24,7 @@ type Startup private () =
                 let converters = options.JsonSerializerOptions.Converters
                 converters.Add(JsonFSharpConverter())
                 converters.Add(JsonStringEnumConverter()))
+            .AddMvcOptions(_.OutputFormatters.Add(CsvOutputFormatter()))
         |> ignore
         // Register the Swagger & OpenApi services
         services.AddSwaggerGen(fun c ->

tests/Swashbuckle.WebApi.Server/Swashbuckle.WebApi.Server.fsproj

@@ -9,6 +9,7 @@
   <ItemGroup>
     <Compile Include="Controllers\Types.fs" />
     <Compile Include="Controllers\ReturnControllers.fs" />
+    <Compile Include="Controllers\ReturnTextControllers.fs" />
     <Compile Include="Controllers\UpdateControllers.fs" />
     <Compile Include="Controllers\ResourceControllers.fs" />
     <Compile Include="Controllers\ValuesController.fs" />