From 1831bd39acfcf3a90415731ee945e86a19906c3b Mon Sep 17 00:00:00 2001
From: Dag Brattli <dag.brattli@cognite.com>
Date: Tue, 16 Dec 2025 23:24:22 +0100
Subject: [PATCH] feat: FastAPI async handlers

---
 .config/dotnet-tools.json |  2 +-
 examples/fastapi/App.fs   | 57 +++++++++++++++++++++++----------------
 2 files changed, 35 insertions(+), 24 deletions(-)

diff --git a/.config/dotnet-tools.json b/.config/dotnet-tools.json
index 9c39f94..f4f80c3 100644
--- a/.config/dotnet-tools.json
+++ b/.config/dotnet-tools.json
@@ -10,7 +10,7 @@
       "rollForward": false
     },
     "fable": {
-      "version": "5.0.0-alpha.20",
+      "version": "5.0.0-alpha.21",
       "commands": [
         "fable"
       ],
diff --git a/examples/fastapi/App.fs b/examples/fastapi/App.fs
index a47b9ec..f0feb6e 100644
--- a/examples/fastapi/App.fs
+++ b/examples/fastapi/App.fs
@@ -2,6 +2,7 @@
 /// Demonstrates how to use Fable.Python.FastAPI with decorator attributes
 module App
 
+open System.Threading.Tasks
 open Fable.Core
 open Fable.Python.FastAPI
 open Fable.Python.Pydantic
@@ -36,36 +37,42 @@ items.Add(item2)
 type API() =
     /// Root endpoint - welcome message
     [<Get("/")>]
-    static member root() : obj =
-        {| message = "Welcome to Fable.Python + FastAPI!"
+    static member root() : Task<obj> = task {
+        return {|
+           message = "Welcome to Fable.Python + FastAPI!"
            version = "1.0.0" |}
+    }
 
     /// Health check endpoint
     [<Get("/health")>]
-    static member health() : obj =
-        {| status = "healthy"
+    static member health() : Task<obj> = task {
+        return {|
+           status = "healthy"
            users_count = users.Count
            items_count = items.Count |}
+        }
 
     /// Get all users
     [<Get("/users")>]
-    static member get_users() : ResizeArray<User> =
-        users
+    static member get_users() : Task<ResizeArray<User>> = task {
+        return users
+    }
 
     /// Get a user by ID
     [<Get("/users/{user_id}")>]
-    static member get_user(user_id: int) : obj =
+    static member get_user(user_id: int) : Task<obj> = task {
         match users |> Seq.tryFind (fun u -> u.Id = user_id) with
-        | Some user -> user :> obj
-        | None -> {| error = "User not found" |}
-
+        | Some user -> return user :> obj
+        | None -> return {| error = "User not found" |}
+    }
     /// Create a new user
     [<Post("/users")>]
-    static member create_user(request: CreateUserRequest) : obj =
+    static member create_user(request: CreateUserRequest) = task {
         let newId = if users.Count = 0 then 1 else (users |> Seq.map (fun u -> u.Id) |> Seq.max) + 1
         let newUser = User(Id = newId, Name = request.Name, Email = request.Email)
         users.Add(newUser)
-        {| status = "created"; user = newUser |}
+        return {| status = "created"; user = newUser |}
+    }
 
     /// Get all items
     [<Get("/items")>]
@@ -74,34 +81,38 @@ type API() =
 
     /// Get an item by ID
     [<Get("/items/{item_id}")>]
-    static member get_item(item_id: int) : obj =
+    static member get_item(item_id: int) : Task<obj> = task {
         match items |> Seq.tryFind (fun i -> i.Id = item_id) with
-        | Some item -> item :> obj
-        | None -> {| error = "Item not found" |}
+        | Some item -> return item :> obj
+        | None -> return {| error = "Item not found" |}
+    }
 
     /// Create a new item
     [<Post("/items")>]
-    static member create_item(request: CreateItemRequest) : obj =
+    static member create_item(request: CreateItemRequest) : Task<obj> = task {
         let newId = if items.Count = 0 then 1 else (items |> Seq.map (fun i -> i.Id) |> Seq.max) + 1
         let newItem = Item(Id = newId, Name = request.Name, Price = request.Price, InStock = request.InStock)
         items.Add(newItem)
-        {| status = "created"; item = newItem |}
+        return {| status = "created"; item = newItem |}
+    }
 
     /// Update an item
     [<Put("/items/{item_id}")>]
-    static member update_item(item_id: int, request: CreateItemRequest) : obj =
+    static member update_item(item_id: int, request: CreateItemRequest) : Task<obj> = task {
         match items |> Seq.tryFindIndex (fun i -> i.Id = item_id) with
         | Some index ->
             let updatedItem = Item(Id = item_id, Name = request.Name, Price = request.Price, InStock = request.InStock)
             items.[index] <- updatedItem
-            {| status = "updated"; item = updatedItem |}
-        | None -> {| error = "Item not found" |}
+            return {| status = "updated"; item = updatedItem |}
+        | None -> return {| error = "Item not found" |}
+    }
 
     /// Delete an item
     [<Delete("/items/{item_id}")>]
-    static member delete_item(item_id: int) : obj =
+    static member delete_item(item_id: int) : Task<obj> = task {
         match items |> Seq.tryFindIndex (fun i -> i.Id = item_id) with
         | Some index ->
             items.RemoveAt(index)
-            {| status = "deleted"; deleted_id = nativeint item_id |}
-        | None -> {| error = "Item not found" |}
+            return {| status = "deleted"; deleted_id = nativeint item_id |}
+        | None -> return {| error = "Item not found" |}
+    }
\ No newline at end of file