Initial support for MSC3931: Room version push rule feature flags (#14520)

* Add support for MSC3931: Room Version Supports push rule condition

* Create experimental flag for future work, and use it to gate MSC3931

* Changelog entry

8 files changed, 76 insertions, 1 deletions

diff --git a/changelog.d/14520.feature b/changelog.d/14520.feature
new file mode 100644
index 0000000000..210acaa8ee
--- /dev/null
+++ b/changelog.d/14520.feature
@@ -0,0 +1 @@
+Add unstable support for an Extensible Events room version (`org.matrix.msc1767.10`) via [MSC1767](https://github.com/matrix-org/matrix-spec-proposals/pull/1767), [MSC3931](https://github.com/matrix-org/matrix-spec-proposals/pull/3931), [MSC3932](https://github.com/matrix-org/matrix-spec-proposals/pull/3932), and [MSC3933](https://github.com/matrix-org/matrix-spec-proposals/pull/3933).
\ No newline at end of file
diff --git a/rust/src/push/evaluator.rs b/rust/src/push/evaluator.rs
index cedd42c54d..e8e3d604ee 100644
--- a/rust/src/push/evaluator.rs
+++ b/rust/src/push/evaluator.rs
@@ -29,6 +29,10 @@ use super::{
 lazy_static! {
     /// Used to parse the `is` clause in the room member count condition.
     static ref INEQUALITY_EXPR: Regex = Regex::new(r"^([=<>]*)([0-9]+)$").expect("valid regex");
+
+    /// Used to determine which MSC3931 room version feature flags are actually known to
+    /// the push evaluator.
+    static ref KNOWN_RVER_FLAGS: Vec<String> = vec![];
 }
 
 /// Allows running a set of push rules against a particular event.
@@ -57,6 +61,13 @@ pub struct PushRuleEvaluator {
 
     /// If msc3664, push rules for related events, is enabled.
     related_event_match_enabled: bool,
+
+    /// If MSC3931 is applicable, the feature flags for the room version.
+    room_version_feature_flags: Vec<String>,
+
+    /// If MSC3931 (room version feature flags) is enabled. Usually controlled by the same
+    /// flag as MSC1767 (extensible events core).
+    msc3931_enabled: bool,
 }
 
 #[pymethods]
@@ -70,6 +81,8 @@ impl PushRuleEvaluator {
         notification_power_levels: BTreeMap<String, i64>,
         related_events_flattened: BTreeMap<String, BTreeMap<String, String>>,
         related_event_match_enabled: bool,
+        room_version_feature_flags: Vec<String>,
+        msc3931_enabled: bool,
     ) -> Result<Self, Error> {
         let body = flattened_keys
             .get("content.body")
@@ -84,6 +97,8 @@ impl PushRuleEvaluator {
             sender_power_level,
             related_events_flattened,
             related_event_match_enabled,
+            room_version_feature_flags,
+            msc3931_enabled,
         })
     }
 
@@ -204,6 +219,15 @@ impl PushRuleEvaluator {
                     false
                 }
             }
+            KnownCondition::RoomVersionSupports { feature } => {
+                if !self.msc3931_enabled {
+                    false
+                } else {
+                    let flag = feature.to_string();
+                    KNOWN_RVER_FLAGS.contains(&flag)
+                        && self.room_version_feature_flags.contains(&flag)
+                }
+            }
         };
 
         Ok(result)
@@ -362,6 +386,8 @@ fn push_rule_evaluator() {
         BTreeMap::new(),
         BTreeMap::new(),
         true,
+        vec![],
+        true,
     )
     .unwrap();
 
diff --git a/rust/src/push/mod.rs b/rust/src/push/mod.rs
index d57800aa4a..eef39f6472 100644
--- a/rust/src/push/mod.rs
+++ b/rust/src/push/mod.rs
@@ -277,6 +277,10 @@ pub enum KnownCondition {
     SenderNotificationPermission {
         key: Cow<'static, str>,
     },
+    #[serde(rename = "org.matrix.msc3931.room_version_supports")]
+    RoomVersionSupports {
+        feature: Cow<'static, str>,
+    },
 }
 
 impl IntoPy<PyObject> for Condition {
@@ -492,6 +496,18 @@ fn test_deserialize_unstable_msc3664_condition() {
 }
 
 #[test]
+fn test_deserialize_unstable_msc3931_condition() {
+    let json =
+        r#"{"kind":"org.matrix.msc3931.room_version_supports","feature":"org.example.feature"}"#;
+
+    let condition: Condition = serde_json::from_str(json).unwrap();
+    assert!(matches!(
+        condition,
+        Condition::Known(KnownCondition::RoomVersionSupports { feature: _ })
+    ));
+}
+
+#[test]
 fn test_deserialize_custom_condition() {
     let json = r#"{"kind":"custom_tag"}"#;
 
diff --git a/stubs/synapse/synapse_rust/push.pyi b/stubs/synapse/synapse_rust/push.pyi
index ceade65ef9..cbeb49663c 100644
--- a/stubs/synapse/synapse_rust/push.pyi
+++ b/stubs/synapse/synapse_rust/push.pyi
@@ -41,6 +41,8 @@ class PushRuleEvaluator:
         notification_power_levels: Mapping[str, int],
         related_events_flattened: Mapping[str, Mapping[str, str]],
         related_event_match_enabled: bool,
+        room_version_feature_flags: list[str],
+        msc3931_enabled: bool,
     ): ...
     def run(
         self,
diff --git a/synapse/api/room_versions.py b/synapse/api/room_versions.py
index e37acb0f1e..1bd1ef3e2b 100644
--- a/synapse/api/room_versions.py
+++ b/synapse/api/room_versions.py
@@ -12,7 +12,7 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Callable, Dict, Optional
+from typing import Callable, Dict, List, Optional
 
 import attr
 
@@ -91,6 +91,12 @@ class RoomVersion:
     msc3787_knock_restricted_join_rule: bool
     # MSC3667: Enforce integer power levels
     msc3667_int_only_power_levels: bool
+    # MSC3931: Adds a push rule condition for "room version feature flags", making
+    # some push rules room version dependent. Note that adding a flag to this list
+    # is not enough to mark it "supported": the push rule evaluator also needs to
+    # support the flag. Unknown flags are ignored by the evaluator, making conditions
+    # fail if used.
+    msc3931_push_features: List[str]
 
 
 class RoomVersions:
@@ -111,6 +117,7 @@ class RoomVersions:
         msc2716_redactions=False,
         msc3787_knock_restricted_join_rule=False,
         msc3667_int_only_power_levels=False,
+        msc3931_push_features=[],
     )
     V2 = RoomVersion(
         "2",
@@ -129,6 +136,7 @@ class RoomVersions:
         msc2716_redactions=False,
         msc3787_knock_restricted_join_rule=False,
         msc3667_int_only_power_levels=False,
+        msc3931_push_features=[],
     )
     V3 = RoomVersion(
         "3",
@@ -147,6 +155,7 @@ class RoomVersions:
         msc2716_redactions=False,
         msc3787_knock_restricted_join_rule=False,
         msc3667_int_only_power_levels=False,
+        msc3931_push_features=[],
     )
     V4 = RoomVersion(
         "4",
@@ -165,6 +174,7 @@ class RoomVersions:
         msc2716_redactions=False,
         msc3787_knock_restricted_join_rule=False,
         msc3667_int_only_power_levels=False,
+        msc3931_push_features=[],
     )
     V5 = RoomVersion(
         "5",
@@ -183,6 +193,7 @@ class RoomVersions:
         msc2716_redactions=False,
         msc3787_knock_restricted_join_rule=False,
         msc3667_int_only_power_levels=False,
+        msc3931_push_features=[],
     )
     V6 = RoomVersion(
         "6",
@@ -201,6 +212,7 @@ class RoomVersions:
         msc2716_redactions=False,
         msc3787_knock_restricted_join_rule=False,
         msc3667_int_only_power_levels=False,
+        msc3931_push_features=[],
     )
     MSC2176 = RoomVersion(
         "org.matrix.msc2176",
@@ -219,6 +231,7 @@ class RoomVersions:
         msc2716_redactions=False,
         msc3787_knock_restricted_join_rule=False,
         msc3667_int_only_power_levels=False,
+        msc3931_push_features=[],
     )
     V7 = RoomVersion(
         "7",
@@ -237,6 +250,7 @@ class RoomVersions:
         msc2716_redactions=False,
         msc3787_knock_restricted_join_rule=False,
         msc3667_int_only_power_levels=False,
+        msc3931_push_features=[],
     )
     V8 = RoomVersion(
         "8",
@@ -255,6 +269,7 @@ class RoomVersions:
         msc2716_redactions=False,
         msc3787_knock_restricted_join_rule=False,
         msc3667_int_only_power_levels=False,
+        msc3931_push_features=[],
     )
     V9 = RoomVersion(
         "9",
@@ -273,6 +288,7 @@ class RoomVersions:
         msc2716_redactions=False,
         msc3787_knock_restricted_join_rule=False,
         msc3667_int_only_power_levels=False,
+        msc3931_push_features=[],
     )
     MSC3787 = RoomVersion(
         "org.matrix.msc3787",
@@ -291,6 +307,7 @@ class RoomVersions:
         msc2716_redactions=False,
         msc3787_knock_restricted_join_rule=True,
         msc3667_int_only_power_levels=False,
+        msc3931_push_features=[],
     )
     V10 = RoomVersion(
         "10",
@@ -309,6 +326,7 @@ class RoomVersions:
         msc2716_redactions=False,
         msc3787_knock_restricted_join_rule=True,
         msc3667_int_only_power_levels=True,
+        msc3931_push_features=[],
     )
     MSC2716v4 = RoomVersion(
         "org.matrix.msc2716v4",
@@ -327,6 +345,7 @@ class RoomVersions:
         msc2716_redactions=True,
         msc3787_knock_restricted_join_rule=False,
         msc3667_int_only_power_levels=False,
+        msc3931_push_features=[],
     )
 
 
diff --git a/synapse/config/experimental.py b/synapse/config/experimental.py
index a503abf364..b3f51fc57d 100644
--- a/synapse/config/experimental.py
+++ b/synapse/config/experimental.py
@@ -128,3 +128,6 @@ class ExperimentalConfig(Config):
 
         # MSC3912: Relation-based redactions.
         self.msc3912_enabled: bool = experimental.get("msc3912_enabled", False)
+
+        # MSC1767 and friends: Extensible Events
+        self.msc1767_enabled: bool = experimental.get("msc1767_enabled", False)
diff --git a/synapse/push/bulk_push_rule_evaluator.py b/synapse/push/bulk_push_rule_evaluator.py
index 75b7e126ca..9cc3da6d91 100644
--- a/synapse/push/bulk_push_rule_evaluator.py
+++ b/synapse/push/bulk_push_rule_evaluator.py
@@ -338,6 +338,10 @@ class BulkPushRuleEvaluator:
             for user_id, level in notification_levels.items():
                 notification_levels[user_id] = int(level)
 
+        room_version_features = event.room_version.msc3931_push_features
+        if not room_version_features:
+            room_version_features = []
+
         evaluator = PushRuleEvaluator(
             _flatten_dict(event),
             room_member_count,
@@ -345,6 +349,8 @@ class BulkPushRuleEvaluator:
             notification_levels,
             related_events,
             self._related_event_match_enabled,
+            room_version_features,
+            self.hs.config.experimental.msc1767_enabled,  # MSC3931 flag
         )
 
         users = rules_by_user.keys()
diff --git a/tests/push/test_push_rule_evaluator.py b/tests/push/test_push_rule_evaluator.py
index fe7c145840..5ababe6a39 100644
--- a/tests/push/test_push_rule_evaluator.py
+++ b/tests/push/test_push_rule_evaluator.py
@@ -62,6 +62,8 @@ class PushRuleEvaluatorTestCase(unittest.TestCase):
             power_levels.get("notifications", {}),
             {} if related_events is None else related_events,
             True,
+            event.room_version.msc3931_push_features,
+            True,
         )
 
     def test_display_name(self) -> None: