fix(k8s): field_manager on the reparent apply + ServiceDict typing (ty)

single_kernel_postgresql/charms/k8s_charm.py

@@ -10,7 +10,7 @@
 import sys
 from functools import cached_property
 from pathlib import Path
-from typing import TYPE_CHECKING, cast
+from typing import TYPE_CHECKING, Any, cast
 
 import psycopg2
 from lightkube import Client
@@ -62,6 +62,9 @@
 class PostgreSQLK8sCharm(AbstractPostgreSQLCharm):
     """PostgreSQL K8s Charm."""
 
+    # COS requirers are constructed charm-side and assigned by the consuming charm.
+    metrics_endpoint: Any = None
+
     # Built by build_k8s_manager() while the abstract __init__ wires the
     # async-replication subsystem; never None on the K8s substrate.
     k8s_manager: K8sManager
@@ -284,9 +287,7 @@ def _restart_metrics_service(self) -> None:
                 Layer(
                     LayerDict({
                         "services": {
-                            K8S_METRICS_SERVER_SERVICE_NAME: cast(
-                                "ServiceDict", self._generate_metrics_service()
-                            )
+                            K8S_METRICS_SERVER_SERVICE_NAME: self._generate_metrics_service()
                         }
                     })
                 ),
@@ -341,7 +342,7 @@ def _generate_metrics_jobs(self, enable_tls: bool) -> list[dict]:
             },
         ]
 
-    def _generate_metrics_service(self) -> dict:
+    def _generate_metrics_service(self) -> "ServiceDict":
         """Generate the metrics exporter service definition (port)."""
         workload = cast("K8sWorkload", self.workload)
         monitoring_password = self.state.get_secret(APP_SCOPE, MONITORING_PASSWORD_KEY)

single_kernel_postgresql/managers/k8s.py

@@ -315,6 +315,7 @@ def reparent_services_on_stop(self) -> None:
                     name=resource.metadata.name,
                     namespace=resource.metadata.namespace,
                     force=True,
+                    field_manager=app_name,
                 )
             except ApiError:
                 logger.exception(

single_kernel_postgresql/workload/k8s.py

@@ -807,7 +807,7 @@ def generate_ldap_service(
 
     def generate_metrics_service(
         self, monitoring_password: str | None, postgresql_service: str
-    ) -> dict:
+    ) -> ServiceDict:
         """Generate the metrics exporter service definition (port)."""
         return {
             "override": "replace",

tests/unit/test_k8s_resources.py

@@ -118,6 +118,9 @@ def test_reparent_services_on_stop(harness, k8s_manager):
     # The same Patroni-created resource is listed twice (Service + Endpoints) and
     # reparented on each sighting — faithful to the charm's double-listing flow.
     assert client.apply.call_count == 4
+    # The charm builds its stop-flow Client with field_manager=self.model.app.name:
+    # lightkube's APPLY patch requires one (bare Client() + apply() raises ValueError).
+    assert all(call.kwargs.get("field_manager") == app for call in client.apply.call_args_list)
 
 
 def test_cleanup_old_cluster_resources_deletes_suffixes(harness, k8s_manager):