Merge pull request #64 from canonical/fix-no-remote-unit-ids-evt

fix error when no remote unit data is passed to relation

pyproject.toml

@@ -8,7 +8,7 @@ build-backend = "setuptools.build_meta"
 [project]
 name = "ops-scenario"
 
-version = "5.3"
+version = "5.3.1"
 
 authors = [
     { name = "Pietro Pasotti", email = "[email protected]" }

scenario/runtime.py

@@ -231,13 +231,18 @@ def _get_event_env(self, state: "State", event: "Event", charm_root: Path):
                         "but you probably should be parametrizing the event with `remote_unit_id` "
                         "to be explicit.",
                     )
-                else:
+                elif len(remote_unit_ids) > 1:
                     remote_unit_id = remote_unit_ids[0]
                     logger.warning(
                         "remote unit ID unset, and multiple remote unit IDs are present; "
                         "We will pick the first one and hope for the best. You should be passing "
                         "`remote_unit_id` to the Event constructor.",
                     )
+                else:
+                    logger.warning(
+                        "remote unit ID unset; no remote unit data present. "
+                        "Is this a realistic scenario?",  # TODO: is it?
+                    )
 
             if remote_unit_id is not None:
                 remote_unit = f"{remote_app_name}/{remote_unit_id}"

scenario/state.py

@@ -193,7 +193,7 @@ def _update_metadata(
 
 
 def normalize_name(s: str):
-    """Event names need underscores instead of dashes."""
+    """Event names, in Scenario, uniformly use underscores instead of dashes."""
     return s.replace("-", "_")
 
 
@@ -927,9 +927,6 @@ def __call__(self, remote_unit_id: Optional[int] = None) -> "Event":
         return self.replace(relation_remote_unit_id=remote_unit_id)
 
     def __post_init__(self):
-        if "-" in self.path:
-            logger.warning(f"Only use underscores in event paths. {self.path!r}")
-
         path = normalize_name(self.path)
         # bypass frozen dataclass
         object.__setattr__(self, "path", path)

tests/test_e2e/test_relations.py

@@ -223,6 +223,42 @@ def callback(charm: CharmBase, event):
     )
 
 
+@pytest.mark.parametrize(
+    "evt_name",
+    ("changed", "broken", "departed", "joined", "created"),
+)
+def test_relation_events_no_remote_units(mycharm, evt_name, caplog):
+    relation = Relation(
+        endpoint="foo",
+        interface="foo",
+        remote_units_data={},  # no units
+    )
+
+    def callback(charm: CharmBase, event):
+        assert event.app  # that's always present
+        assert not event.unit
+
+    mycharm._call = callback
+
+    trigger(
+        State(
+            relations=[
+                relation,
+            ],
+        ),
+        getattr(relation, f"{evt_name}_event"),
+        mycharm,
+        meta={
+            "name": "local",
+            "requires": {
+                "foo": {"interface": "foo"},
+            },
+        },
+    )
+
+    assert "remote unit ID unset; no remote unit data present" in caplog.text
+
+
 @pytest.mark.parametrize("data", (set(), {}, [], (), 1, 1.0, None, b""))
 def test_relation_unit_data_bad_types(mycharm, data):
     with pytest.raises(StateValidationError):