patch: async handlers resolution

Author: lucasteles

FSharp.MinimalApi.Interop/AsParameter.cs

@@ -1,18 +1,23 @@
-namespace FSharp.MinimalApi;
+using System.Reflection;
+
+namespace FSharp.MinimalApi;
 
 using Microsoft.FSharp.Core;
 using Microsoft.AspNetCore.Http;
 
 public static class AsParameters
 {
     public static Delegate Of<TParam, TResult>(FSharpFunc<TParam, TResult> requestDelegate) =>
-        typeof(TParam) == typeof(Unit)
-            ? typeof(TResult) == typeof(Unit)
-                ? void () => requestDelegate.Invoke(Operators.Unchecked.DefaultOf<TParam>())
-                : () => requestDelegate.Invoke(Operators.Unchecked.DefaultOf<TParam>())
-            : typeof(TResult) == typeof(Unit)
-                ? void ([AsParameters] TParam parameters) => requestDelegate.Invoke(parameters)
-                : ([AsParameters] TParam parameters) => requestDelegate.Invoke(parameters);
+        typeof(TResult).IsGenericType &&
+        typeof(TResult).GetGenericTypeDefinition() == typeof(Task<>)
+            ? CreateAsTask(requestDelegate)
+            : typeof(TParam) == typeof(Unit)
+                ? typeof(TResult) == typeof(Unit)
+                    ? void () => requestDelegate.Invoke(Operators.Unchecked.DefaultOf<TParam>())
+                    : () => requestDelegate.Invoke(Operators.Unchecked.DefaultOf<TParam>())
+                : typeof(TResult) == typeof(Unit)
+                    ? void ([AsParameters] TParam parameters) => requestDelegate.Invoke(parameters)
+                    : ([AsParameters] TParam parameters) => requestDelegate.Invoke(parameters);
 
     public static Delegate OfTask<TParam, TResult>(
         FSharpFunc<TParam, Task<TResult>> requestDelegate) =>
@@ -25,4 +30,15 @@ public static Delegate OfTask<TParam, TResult>(
             : typeof(TResult) == typeof(Unit)
                 ? Task ([AsParameters] TParam parameters) => requestDelegate.Invoke(parameters)
                 : ([AsParameters] TParam parameters) => requestDelegate.Invoke(parameters);
+
+    static Delegate CreateAsTask<TParam, TResult>(FSharpFunc<TParam, TResult> requestDelegate)
+    {
+        var underType = typeof(TResult).GetGenericArguments()[0];
+        var method =
+            typeof(AsParameters).GetMethod(nameof(OfTask),
+                    BindingFlags.Public | BindingFlags.Static)!
+                .MakeGenericMethod(typeof(TParam), underType);
+
+        return (Delegate) method.Invoke(null, new object?[] {requestDelegate})!;
+    }
 }

FSharp.MinimalApi/Builder/EndpointHandlerBuilder.fs

@@ -61,15 +61,11 @@ type RouterBaseBuilder<'state>() =
     //****************************************************************************************************
     // MapGet
     [<CustomOperation(HttpMethodName.Get)>]
-    member this.MapGet(s, route, f: Delegate, ?config) = this.get s route f config
-
-    [<CustomOperation(HttpMethodName.Get)>]
-    member this.MapGet(s, route, f: 'p -> 'r, ?config) =
+    member inline this.MapGet(s, route, f: 'p -> 'r, ?config) =
         this.get s route (AsParameters.Of f) config
 
     [<CustomOperation(HttpMethodName.Get)>]
-    member this.MapGet(s, route, f: 'p -> Task<'r>, ?config) =
-        this.get s route (AsParameters.OfTask f) config
+    member this.MapGet(s, route, f: Delegate, ?config) = this.get s route f config
 
     // MapPost
     [<CustomOperation(HttpMethodName.Post)>]
@@ -79,10 +75,6 @@ type RouterBaseBuilder<'state>() =
     member this.MapPost(s, route, f: 'p -> 'r, ?config) =
         this.post s route (AsParameters.Of f) config
 
-    [<CustomOperation(HttpMethodName.Post)>]
-    member this.MapPost(s, route, f: 'p -> Task<'r>, ?config) =
-        this.post s route (AsParameters.OfTask f) config
-
     // MapPut
     [<CustomOperation(HttpMethodName.Put)>]
     member this.MapPut(s, route, f: Delegate, ?config) = this.put s route f config
@@ -91,10 +83,6 @@ type RouterBaseBuilder<'state>() =
     member this.MapPut(s, route, f: 'p -> 'r, ?config) =
         this.put s route (AsParameters.Of f) config
 
-    [<CustomOperation(HttpMethodName.Put)>]
-    member this.MapPut(s, route, f: 'p -> Task<'r>, ?config) =
-        this.put s route (AsParameters.OfTask f) config
-
     // MapDelete
     [<CustomOperation(HttpMethodName.Delete)>]
     member this.MapDelete(s, route, f: Delegate, ?config) = this.delete s route f config
@@ -103,11 +91,6 @@ type RouterBaseBuilder<'state>() =
     member this.MapDelete(s, route, f: 'p -> 'r, ?config) =
         this.delete s route (AsParameters.Of f) config
 
-    [<CustomOperation(HttpMethodName.Delete)>]
-    member this.MapDelete(s, route, f: 'p -> Task<'r>, ?config) =
-        this.delete s route (AsParameters.OfTask f) config
-
-
     //****************************************************************************************************
     // TypedResult Maps
     //****************************************************************************************************