WIP: draft work to test Juju's Pebble Notices integration

ops/charm.py

@@ -711,6 +711,38 @@ class PebbleReadyEvent(WorkloadEvent):
     """
 
 
+# TODO(benhoyt): should these class names have a "Pebble" prefix?
+class PebbleNoticeEvent(WorkloadEvent):
+    def __init__(self, handle: 'Handle', workload: 'model.Container', notice_type: str, notice_key: str):
+        super().__init__(handle, workload)
+        self._notice_type = notice_type
+        self._notice_key = notice_key
+
+    def snapshot(self) -> Dict[str, Any]:
+        d = super().snapshot()
+        d['notice_type'] = self._notice_type
+        d['notice_key'] = self._notice_key
+        return d
+
+    def restore(self, snapshot: Dict[str, Any]):
+        self._notice_type = snapshot.pop('notice_type')
+        self._notice_key = snapshot.pop('notice_key')
+        super().restore(snapshot)
+
+    @property
+    def notice(self) -> model.Notice:
+        # TODO(benhoyt): should probably use notice-get hook tool, but only lazily if
+        #                attributes other than type or key are accessed?
+        return model.Notice(type=self._notice_type, key=self._notice_key)
+
+
+class PebbleCustomNoticeEvent(PebbleNoticeEvent):
+    pass
+
+class PebbleChangeUpdatedEvent(PebbleNoticeEvent):
+    pass
+
+
 class SecretEvent(HookEvent):
     """Base class for all secret events."""
 
@@ -1083,6 +1115,8 @@ def __init__(self, framework: Framework):
         for container_name in self.framework.meta.containers:
             container_name = container_name.replace('-', '_')
             self.on.define_event(f"{container_name}_pebble_ready", PebbleReadyEvent)
+            self.on.define_event(f"{container_name}_pebble_change_updated", PebbleChangeUpdatedEvent)
+            self.on.define_event(f"{container_name}_pebble_custom_notice", PebbleCustomNoticeEvent)
 
     @property
     def app(self) -> model.Application:

ops/main.py

@@ -153,7 +153,12 @@ def _get_event_args(charm: 'ops.charm.CharmBase',
     if issubclass(event_type, ops.charm.WorkloadEvent):
         workload_name = os.environ['JUJU_WORKLOAD_NAME']
         container = model.unit.get_container(workload_name)
-        return [container], {}
+        args: List[Any] = [container]
+        if issubclass(event_type, ops.charm.PebbleNoticeEvent):
+            notice_type = os.environ['JUJU_NOTICE_TYPE']
+            notice_key = os.environ['JUJU_NOTICE_KEY']
+            args.extend([notice_type, notice_key])
+        return args, {}
     elif issubclass(event_type, ops.charm.SecretEvent):
         args: List[Any] = [
             os.environ['JUJU_SECRET_ID'],

ops/model.py

@@ -1082,6 +1082,15 @@ def __repr__(self):
                 ).format(self=self)
 
 
+# TODO(benhoyt): where should this go in the file?
+@dataclasses.dataclass(frozen=True)
+class Notice:
+    type: str
+    key: str
+
+    # TODO(benhoyt): add other attributes got using notice-get hook tool
+
+
 class Secret:
     """Represents a single secret in the model.