Initial implementation of MSC3981: recursive relations API (#15315)

Adds an optional keyword argument to the /relations API which
will recurse a limited number of event relationships.

This will cause the API to return not just the events related to the
parent event, but also events related to those related to the parent
event, etc.

This is disabled by default behind an experimental configuration
flag and is currently implemented using prefixed parameters.

1 files changed, 120 insertions, 0 deletions

diff --git a/tests/rest/client/test_relations.py b/tests/rest/client/test_relations.py

index fbbbcb23f1..75439416c1 100644
--- a/tests/rest/client/test_relations.py
+++ b/tests/rest/client/test_relations.py
@@ -30,6 +30,7 @@ from tests import unittest
 from tests.server import FakeChannel
 from tests.test_utils import make_awaitable
 from tests.test_utils.event_injection import inject_event
+from tests.unittest import override_config
 
 
 class BaseRelationsTestCase(unittest.HomeserverTestCase):
@@ -949,6 +950,125 @@ class RelationPaginationTestCase(BaseRelationsTestCase):
             )
 
 
+class RecursiveRelationTestCase(BaseRelationsTestCase):
+    @override_config({"experimental_features": {"msc3981_recurse_relations": True}})
+    def test_recursive_relations(self) -> None:
+        """Generate a complex, multi-level relationship tree and query it."""
+        # Create a thread with a few messages in it.
+        channel = self._send_relation(RelationTypes.THREAD, "m.room.test")
+        thread_1 = channel.json_body["event_id"]
+
+        channel = self._send_relation(RelationTypes.THREAD, "m.room.test")
+        thread_2 = channel.json_body["event_id"]
+
+        # Add annotations.
+        channel = self._send_relation(
+            RelationTypes.ANNOTATION, "m.reaction", "a", parent_id=thread_2
+        )
+        annotation_1 = channel.json_body["event_id"]
+
+        channel = self._send_relation(
+            RelationTypes.ANNOTATION, "m.reaction", "b", parent_id=thread_1
+        )
+        annotation_2 = channel.json_body["event_id"]
+
+        # Add a reference to part of the thread, then edit the reference and annotate it.
+        channel = self._send_relation(
+            RelationTypes.REFERENCE, "m.room.test", parent_id=thread_2
+        )
+        reference_1 = channel.json_body["event_id"]
+
+        channel = self._send_relation(
+            RelationTypes.ANNOTATION, "m.reaction", "c", parent_id=reference_1
+        )
+        annotation_3 = channel.json_body["event_id"]
+
+        channel = self._send_relation(
+            RelationTypes.REPLACE,
+            "m.room.test",
+            parent_id=reference_1,
+        )
+        edit = channel.json_body["event_id"]
+
+        # Also more events off the root.
+        channel = self._send_relation(RelationTypes.ANNOTATION, "m.reaction", "d")
+        annotation_4 = channel.json_body["event_id"]
+
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/relations/{self.parent_id}"
+            "?dir=f&limit=20&org.matrix.msc3981.recurse=true",
+            access_token=self.user_token,
+        )
+        self.assertEqual(200, channel.code, channel.json_body)
+
+        # The above events should be returned in creation order.
+        event_ids = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(
+            event_ids,
+            [
+                thread_1,
+                thread_2,
+                annotation_1,
+                annotation_2,
+                reference_1,
+                annotation_3,
+                edit,
+                annotation_4,
+            ],
+        )
+
+    @override_config({"experimental_features": {"msc3981_recurse_relations": True}})
+    def test_recursive_relations_with_filter(self) -> None:
+        """The event_type and rel_type still apply."""
+        # Create a thread with a few messages in it.
+        channel = self._send_relation(RelationTypes.THREAD, "m.room.test")
+        thread_1 = channel.json_body["event_id"]
+
+        # Add annotations.
+        channel = self._send_relation(
+            RelationTypes.ANNOTATION, "m.reaction", "b", parent_id=thread_1
+        )
+        annotation_1 = channel.json_body["event_id"]
+
+        # Add a reference to part of the thread, then edit the reference and annotate it.
+        channel = self._send_relation(
+            RelationTypes.REFERENCE, "m.room.test", parent_id=thread_1
+        )
+        reference_1 = channel.json_body["event_id"]
+
+        channel = self._send_relation(
+            RelationTypes.ANNOTATION, "org.matrix.reaction", "c", parent_id=reference_1
+        )
+        annotation_2 = channel.json_body["event_id"]
+
+        # Fetch only annotations, but recursively.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/relations/{self.parent_id}/{RelationTypes.ANNOTATION}"
+            "?dir=f&limit=20&org.matrix.msc3981.recurse=true",
+            access_token=self.user_token,
+        )
+        self.assertEqual(200, channel.code, channel.json_body)
+
+        # The above events should be returned in creation order.
+        event_ids = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(event_ids, [annotation_1, annotation_2])
+
+        # Fetch only m.reactions, but recursively.
+        channel = self.make_request(
+            "GET",
+            f"/_matrix/client/v1/rooms/{self.room}/relations/{self.parent_id}/{RelationTypes.ANNOTATION}/m.reaction"
+            "?dir=f&limit=20&org.matrix.msc3981.recurse=true",
+            access_token=self.user_token,
+        )
+        self.assertEqual(200, channel.code, channel.json_body)
+
+        # The above events should be returned in creation order.
+        event_ids = [ev["event_id"] for ev in channel.json_body["chunk"]]
+        self.assertEqual(event_ids, [annotation_1])
+
+
 class BundledAggregationsTestCase(BaseRelationsTestCase):
     """
     See RelationsTestCase.test_edit for a similar test for edits.