Merge pull request canonical#145 from canonical/config-persistence

fixed config mutation in state

pyproject.toml

@@ -8,7 +8,7 @@ build-backend = "setuptools.build_meta"
 [project]
 name = "ops-scenario"
 
-version = "6.1.0"
+version = "6.1.1"
 
 authors = [
     { name = "Pietro Pasotti", email = "pietro.pasotti@canonical.com" }

scenario/consistency_checker.py

@@ -353,7 +353,6 @@ def check_config_consistency(
             )
             continue
 
-        # todo unify with snapshot's when merged.
         converters = {
             "string": str,
             "int": int,

scenario/mocking.py

@@ -263,7 +263,7 @@ def relation_list(self, relation_id: int) -> Tuple[str, ...]:
         )
 
     def config_get(self):
-        state_config = self._state.config
+        state_config = self._state.config.copy()  # dedup or we'll mutate the state!
 
         # add defaults
         charm_config = self._charm_spec.config

tests/test_e2e/test_config.py

@@ -2,7 +2,7 @@
 from ops.charm import CharmBase
 from ops.framework import Framework
 
-from scenario.state import Event, Network, Relation, State, _CharmSpec
+from scenario.state import State
 from tests.helpers import trigger
 
 
@@ -53,9 +53,49 @@ def check_cfg(charm: CharmBase):
         config={
             "options": {
                 "foo": {"type": "string"},
-                "baz": {"type": "integer", "default": 2},
+                "baz": {"type": "int", "default": 2},
                 "qux": {"type": "boolean", "default": False},
             },
         },
         post_event=check_cfg,
     )
+
+
+@pytest.mark.parametrize(
+    "cfg_in",
+    (
+        {"foo": "bar"},
+        {"baz": 4, "foo": "bar"},
+        {"baz": 4, "foo": "bar", "qux": True},
+    ),
+)
+def test_config_in_not_mutated(mycharm, cfg_in):
+    class MyCharm(CharmBase):
+        def __init__(self, framework: Framework):
+            super().__init__(framework)
+            for evt in self.on.events().values():
+                self.framework.observe(evt, self._on_event)
+
+        def _on_event(self, event):
+            # access the config to trigger a config-get
+            foo_cfg = self.config["foo"]
+            baz_cfg = self.config["baz"]
+            qux_cfg = self.config["qux"]
+
+    state_out = trigger(
+        State(
+            config=cfg_in,
+        ),
+        "update_status",
+        MyCharm,
+        meta={"name": "foo"},
+        config={
+            "options": {
+                "foo": {"type": "string"},
+                "baz": {"type": "int", "default": 2},
+                "qux": {"type": "boolean", "default": False},
+            },
+        },
+    )
+    # check config was not mutated by scenario
+    assert state_out.config == cfg_in