Fix kernel shutdown behavior

jupyter_server/services/kernels/kernelmanager.py

@@ -398,10 +398,9 @@ def shutdown_kernel(self, kernel_id, now=False, restart=False):
         if kernel_id in self._pending_kernel_tasks:
             task = self._pending_kernel_tasks.pop(kernel_id)
             task.cancel()
-            return
-
-        self.stop_watching_activity(kernel_id)
-        self.stop_buffering(kernel_id)
+        else:
+            self.stop_watching_activity(kernel_id)
+            self.stop_buffering(kernel_id)
 
         self.pinned_superclass.shutdown_kernel(self, kernel_id, now=now, restart=restart)
 
@@ -661,10 +660,9 @@ async def shutdown_kernel(self, kernel_id, now=False, restart=False):
         if kernel_id in self._pending_kernel_tasks:
             task = self._pending_kernel_tasks.pop(kernel_id)
             task.cancel()
-            return
-
-        self.stop_watching_activity(kernel_id)
-        self.stop_buffering(kernel_id)
+        else:
+            self.stop_watching_activity(kernel_id)
+            self.stop_buffering(kernel_id)
 
         # Finish shutting down the kernel before clearing state to avoid a race condition.
         return await self.pinned_superclass.shutdown_kernel(

tests/services/kernels/test_api.py

@@ -158,7 +158,7 @@ async def test_main_kernel_handler(jp_fetch, jp_base_url, jp_serverapp, pending_
 
 
 @pytest.mark.timeout(TEST_TIMEOUT)
-async def test_kernel_handler(jp_fetch, pending_kernel_is_ready):
+async def test_kernel_handler(jp_fetch, jp_serverapp, pending_kernel_is_ready):
     # Create a kernel
     r = await jp_fetch(
         "api", "kernels", method="POST", body=json.dumps({"name": NATIVE_KERNEL_NAME})