prompt check before proceed

Author: reneeli@microsoft.com

src/aks-preview/azext_aks_preview/managed_cluster_decorator.py

@@ -2821,7 +2821,13 @@ def get_migrate_vmas_to_vms(self) -> bool:
 
         :return: bool
         """
-        return self.raw_param.get("migrate_vmas_to_vms")
+        migrate_vmas_to_vms = self.raw_param.get("migrate_vmas_to_vms")
+        if migrate_vmas_to_vms:
+            msg = "This node image upgrade operation will run across every node pool in the cluster " \
+            "and might take a while. Do you wish to continue?"
+            if not self.context.get_yes() and not prompt_y_n(msg, default="n"):
+                return None
+        return migrate_vmas_to_vms
 
 
 # pylint: disable=too-many-public-methods

src/aks-preview/azext_aks_preview/tests/latest/test_aks_commands.py

@@ -15895,7 +15895,7 @@ def test_aks_loadbalancer_commands(
     #     # update -- migrate vmas to vma
     #     update_cmd = (
     #         "aks update --resource-group {resource_group} --name {name} "
-    #         "--migrate-vmas-to-vms "
+    #         "--migrate-vmas-to-vms --yes "
     #     )
     #     self.cmd(update_cmd, checks=[
     #         self.check('provisioningState', 'Succeeded'),