fix(revisions): publish a delta for a collected model instead of raising

src/trame_dataclass/module/revisions.py

@@ -48,9 +48,14 @@ def snapshot(self, obj):
 
     def push_delta(self, msg):
         """Publish a state delta to all connected clients via the ``trame.dataclass.publish`` topic."""
-        # Only a live model flushes, and every model registers itself on creation, so
-        # its id always resolves and every publication carries a revision.
-        key = self._track_revisions(self.find_instance(msg["id"]))
+        obj = self.find_instance(msg["id"])
+        if obj is None:
+            # The registry holds weak references, so a delta flushed after its model
+            # was collected has no instance. Publish it without a revision, as
+            # get_state already answers {"id": ..., "state": None} for such an id.
+            self.publish("trame.dataclass.publish", msg)
+            return
+        key = self._track_revisions(obj)
         revision = self.state_revisions[key] + 1
         self.state_revisions[key] = revision
         self.publish("trame.dataclass.publish", {**deepcopy(msg), "revision": revision})

tests/test_protocol_revisions.py

@@ -143,6 +143,18 @@ def test_a_retired_id_keeps_the_existing_missing_state_protocol(version):
     assert p.get_state("gone") == {"id": "gone", "state": None}
 
 
+def test_a_delta_for_a_collected_model_is_published_without_a_revision(version):
+    """A delta flushed after its model was collected must not raise."""
+    p, a = protocol(version), version.Sample()
+    retired = a._id
+    del a
+    gc.collect()
+    p.push_delta({"id": retired, "state": {"value": 1}})
+    published = p.publish.call_args.args[1]
+    assert published == {"id": retired, "state": {"value": 1}}
+    assert "revision" not in published
+
+
 def test_a_model_that_compares_by_value_can_still_be_read_and_revised(version):
     """MUTATION (run): key ``state_revisions`` by ``obj``. Both calls raise TypeError."""
     p, a = protocol(version), version.ValueEqual()