feat: use event for information

Using the event reveals all the information required, no need to ask
for the information from somewhere else.

Author: SimonRichardson

src/charm.py

@@ -15,7 +15,7 @@
 from charms.certificate_transfer_interface.v1.certificate_transfer import (
     CertificateTransferRequires,
 )
-from charms.data_platform_libs.v0.s3 import S3Requirer
+from charms.data_platform_libs.v0.s3 import CredentialsChangedEvent, S3Requirer
 from ops.charm import CharmBase, CollectStatusEvent
 from ops.framework import StoredState
 from ops.charm import InstallEvent, RelationJoinedEvent, RelationDepartedEvent
@@ -365,13 +365,18 @@ def _update_charm_tracing_config(self):
             ca_cert=self._stored.ca_cert,
         )
 
-    def _on_s3_credentials_changed(self, _event):
+    def _on_s3_credentials_changed(self, event: CredentialsChangedEvent):
         """Handle new or updated S3 credentials."""
         if self.unit.is_leader():
-            credentials = self._s3.get_s3_connection_info()
+            credentials = {
+                'access_key': event.access_key,
+                'secret_key': event.secret_key,
+                'endpoint': event.endpoint,
+            }
             self._stored.s3_credentials = credentials
 
             try:
+                logger.info("applying new S3 credentials")
                 self._control_socket.add_s3_credentials(credentials)
                 self.unit.status = MaintenanceStatus("applying s3 credentials")
             except Exception as exc:  # pragma: no cover - defensive
@@ -383,10 +388,10 @@ def _on_s3_credentials_gone(self, _event):
         if self.unit.is_leader():
             try:
                 self._control_socket.remove_s3_credentials()
+                self._stored.s3_credentials = dict()
             except Exception as exc:  # pragma: no cover - defensive
                 logger.error("failed to remove S3 credentials: %s", exc)
                 self.unit.status = BlockedStatus("failed to remove s3 credentials")
-        self._stored.s3_credentials = dict()
 
 def metrics_username(relation: Relation) -> str:
     """

tests/test_charm.py

@@ -501,16 +501,16 @@ def test_s3_relation_credentials_changed(self, mock_add_s3_credentials):
             },
         )
 
+        expected_credentials = {
+            "access_key": "ak",
+            "secret_key": "sk",
+            "endpoint": "https://s3.example",
+        }
         self.assertEqual(
             harness.charm._stored.s3_credentials,
-            {
-                "access-key": "ak",
-                "secret-key": "sk",
-                "bucket": "test-bucket",
-                "endpoint": "https://s3.example",
-            },
+            expected_credentials,
         )
-        mock_add_s3_credentials.assert_called_once_with(harness.charm._stored.s3_credentials)
+        mock_add_s3_credentials.assert_called_once_with(expected_credentials)
         self.assertIsInstance(harness.charm.unit.status, MaintenanceStatus)
 
     @patch(
@@ -532,7 +532,7 @@ def test_s3_relation_credentials_changed_failure_sets_blocked(self, _mock_add):
 
         self.assertEqual(
             harness.charm._stored.s3_credentials,
-            {"access-key": "ak", "secret-key": "sk", "bucket": "test-bucket"},
+            {"access_key": "ak", "secret_key": "sk", "endpoint": None},
         )
         self.assertIsInstance(harness.charm.unit.status, BlockedStatus)
         self.assertIn(
@@ -570,7 +570,10 @@ def test_s3_relation_credentials_updated(self, mock_add_s3_credentials):
             "s3-integrator",
             {"access-key": "ak", "secret-key": "sk", "bucket": "test-bucket"},
         )
-        self.assertEqual(harness.charm._stored.s3_credentials["access-key"], "ak")
+        self.assertEqual(
+            harness.charm._stored.s3_credentials,
+            {"access_key": "ak", "secret_key": "sk", "endpoint": None},
+        )
 
         harness.update_relation_data(
             relation_id,
@@ -579,10 +582,10 @@ def test_s3_relation_credentials_updated(self, mock_add_s3_credentials):
         )
         self.assertEqual(
             harness.charm._stored.s3_credentials,
-            {"access-key": "ak2", "secret-key": "sk2", "bucket": "test-bucket"},
+            {"access_key": "ak2", "secret_key": "sk2", "endpoint": None},
         )
         mock_add_s3_credentials.assert_called_with(
-            {"access-key": "ak2", "secret-key": "sk2", "bucket": "test-bucket"}
+            {"access_key": "ak2", "secret_key": "sk2", "endpoint": None}
         )
         self.assertIsInstance(harness.charm.unit.status, MaintenanceStatus)
 
@@ -612,7 +615,8 @@ def test_s3_relation_credentials_gone(self, *_):
             "s3-integrator",
             {"access-key": "ak", "secret-key": "sk"},
         )
-        self.assertIn("access-key", harness.charm._stored.s3_credentials)
+        expected_credentials = {"access_key": "ak", "secret_key": "sk", "endpoint": None}
+        self.assertEqual(harness.charm._stored.s3_credentials, expected_credentials)
 
         harness.remove_relation(relation_id)
         self.assertEqual(harness.charm._stored.s3_credentials, {})
@@ -654,7 +658,10 @@ def test_s3_relation_credentials_gone_failure_sets_blocked(self, _mock_remove):
 
         harness.remove_relation(relation_id)
 
-        self.assertEqual(harness.charm._stored.s3_credentials, {})
+        self.assertEqual(
+            harness.charm._stored.s3_credentials,
+            {"access_key": "ak", "secret_key": "sk", "endpoint": None},
+        )
         self.assertIsInstance(harness.charm.unit.status, BlockedStatus)
         self.assertIn("failed to remove s3 credentials", harness.charm.unit.status.message)