[Python] Fix mainloop async warnings

src/fable-library-py/fable_library/async_.py

@@ -189,6 +189,23 @@ def callback(conts: Continuations[_T]) -> None:
     return from_continuations(callback)
 
 
+def run_in_loop(computation: Callable[..., None]) -> Any:
+    """Run a computation on the event loop.
+
+    If no event loop is running, then one is created and run.
+    """
+
+    async def runner() -> None:
+        return computation()
+
+    try:
+        asyncio.get_running_loop()
+    except RuntimeError:
+        return asyncio.run(runner())
+    else:
+        return computation()
+
+
 def start_with_continuations(
     computation: Async[_T],
     continuation: Callable[[_T], None] | None = None,
@@ -214,7 +231,10 @@ def start_with_continuations(
         cancellation_token or default_cancellation_token,
     )
 
-    return computation(ctx)
+    def runner() -> None:
+        computation(ctx)
+
+    run_in_loop(runner)
 
 
 def start_as_task(
@@ -281,20 +301,7 @@ def start_immediate(
     Runs an asynchronous computation, starting immediately on the
     current operating system thread
     """
-    try:
-        asyncio.get_event_loop()
-    except RuntimeError:
-
-        async def runner() -> None:
-            return start_with_continuations(
-                computation, cancellation_token=cancellation_token
-            )
-
-        return asyncio.run(runner())
-    else:
-        return start_with_continuations(
-            computation, cancellation_token=cancellation_token
-        )
+    start_with_continuations(computation, cancellation_token=cancellation_token)
 
 
 _executor: ThreadPoolExecutor | None = None

src/fable-library-py/fable_library/async_builder.py

@@ -256,7 +256,7 @@ def protected_bind(
     computation: Callable[[IAsyncContext[_T]], None],
     binder: Callable[[_T], Async[_U]],
 ) -> Async[_U]:
-    def cont(ctx: IAsyncContext[_T]):
+    def cont(ctx: IAsyncContext[_U]) -> None:
         def on_success(x: _T) -> None:
             try:
                 binder(x)(ctx)