Allow the charm to set extra-labels it wishes to manage not set by user

ops/charms/node_base.py

@@ -62,6 +62,7 @@ def __init__(
         kubectl: Optional[PathLike] = "/snap/bin/kubectl",
         user_label_key: str = "labels",
         timeout: Optional[PositiveInt] = None,
+        raise_invalid_label: bool = False,
     ) -> None:
         """Initialize the LabelMaker.
 
@@ -71,6 +72,7 @@ def __init__(
             kubectl (Optional[PathLike], optional): Path to the kubectl binary. Defaults to "/snap/bin/kubectl".
             user_label_key (str, optional): The key in the charm config where the user labels are stored. Defaults to "labels".
             timeout (Optional[PositiveInt], optional): Number of seconds to retry a command. Defaults to None.
+            raise_invalid_label (bool, optional): Whether to raise an exception when an invalid label is found. Defaults to False.
         """
         super().__init__(parent=charm, key="NodeBase")
         self.charm = charm
@@ -79,6 +81,7 @@ def __init__(
         self.user_labels_key = user_label_key
         self.timeout = DEFAULT_TIMEOUT if timeout is None else timeout
         self._stored.set_default(current_labels=dict())
+        self._raise_invalid_label = raise_invalid_label
 
     def _retried_call(
         self, cmd: List[str], retry_msg: str, timeout: Optional[int] = None
@@ -185,7 +188,9 @@ def user_labels(self) -> Mapping[str, str]:
             try:
                 key, val = item.split("=")
             except ValueError:
-                log.info(f"Skipping malformed option: {item}.")
+                if self._raise_invalid_label:
+                    raise self.NodeLabelError(f"Malformed label: {item}.")
+                log.error(f"Skipping Malformed label: {item}.")
             else:
                 user_labels[key] = val
         return user_labels
@@ -210,8 +215,12 @@ def apply_node_labels(self) -> None:
 
             # Add any new labels.
             for key, val in user_labels.items():
-                self.set_label(key, val)
-                self._stored.current_labels[key] = val
+                if val.endswith("-"):
+                    # Remove the label if the value ends with a dash.
+                    self.remove_label(key)
+                else:
+                    self.set_label(key, val)
+                    self._stored.current_labels[key] = val
 
             # Set the juju-application and juju-charm labels.
             self.set_label("juju-application", self.charm.model.app.name)

ops/tests/unit/test_ops.py

@@ -127,14 +127,19 @@ def test_active_labels_apply_layers_from_config(
     subprocess_run, harness, label_maker, caplog
 ):
     harness.update_config(
-        {"my-labels": "node-role.kubernetes.io/control-plane= invalid"}
+        {
+            "my-labels": "node-role.kubernetes.io/control-plane= invalid extra-label.removable-"
+        }
     )
     subprocess_run.return_value = RunResponse(0)
-    label_maker._stored.current_labels = {"node-role.kubernetes.io/worker": ""}
+    label_maker._stored.current_labels = {
+        "node-role.kubernetes.io/worker": "",
+        "extra-label.removable": "",
+    }
     label_maker.apply_node_labels()
-    assert "Skipping malformed option: invalid." in caplog.messages
+    assert "Skipping Malformed label: invalid." in caplog.messages
     assert label_maker._stored.current_labels == {
-        "node-role.kubernetes.io/control-plane": ""
+        "node-role.kubernetes.io/control-plane": "",
     }
     subprocess_run.assert_has_calls(
         [
@@ -151,10 +156,19 @@ def test_active_labels_apply_layers_from_config(
             )
             for label_args in [
                 ("node-role.kubernetes.io/worker-",),
+                ("extra-label.removable-",),
                 ("node-role.kubernetes.io/control-plane=", "--overwrite"),
                 ("juju-application=test-charm", "--overwrite"),
                 ("juju-charm=test-charm", "--overwrite"),
                 ("juju.io/cloud-",),
             ]
         ],
     )
+
+
+def test_raise_invalid_label(subprocess_run, harness, label_maker):
+    harness.update_config({"my-labels": "this=isn't=valid"})
+    subprocess_run.return_value = RunResponse(0)
+    label_maker._raise_invalid_label = True
+    with pytest.raises(node_base.LabelMaker.NodeLabelError):
+        label_maker.apply_node_labels()