Add default push rules for live location share start (MSCxxxx draft)

Underride rules .io.element.rule.beacon_info(_one_to_one) matching
org.matrix.msc3672.beacon_info with content.live == true, so recipients
are pushed when someone starts a live location share (incl. E2EE rooms,
since beacon_info is an unencrypted state event). Gated behind
experimental_features.mscxxxx_beacon_push_rules_enabled; rule ids and
flag to be renamed once the MSC is numbered.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

rust/src/push/base_rules.rs

@@ -721,6 +721,43 @@ pub const BASE_APPEND_UNDERRIDE_RULES: &[PushRule] = &[
         default: true,
         default_enabled: true,
     },
+    PushRule {
+        rule_id: Cow::Borrowed("global/underride/.io.element.rule.beacon_info_one_to_one"),
+        priority_class: 1,
+        conditions: Cow::Borrowed(&[
+            Condition::Known(KnownCondition::RoomMemberCount {
+                is: Some(Cow::Borrowed("2")),
+            }),
+            Condition::Known(KnownCondition::EventMatch(EventMatchCondition {
+                key: Cow::Borrowed("type"),
+                pattern: Cow::Borrowed("org.matrix.msc3672.beacon_info"),
+            })),
+            Condition::Known(KnownCondition::EventPropertyIs(EventPropertyIsCondition {
+                key: Cow::Borrowed("content.live"),
+                value: Cow::Owned(SimpleJsonValue::Bool(true)),
+            })),
+        ]),
+        actions: Cow::Borrowed(&[Action::Notify, SOUND_ACTION]),
+        default: true,
+        default_enabled: true,
+    },
+    PushRule {
+        rule_id: Cow::Borrowed("global/underride/.io.element.rule.beacon_info"),
+        priority_class: 1,
+        conditions: Cow::Borrowed(&[
+            Condition::Known(KnownCondition::EventMatch(EventMatchCondition {
+                key: Cow::Borrowed("type"),
+                pattern: Cow::Borrowed("org.matrix.msc3672.beacon_info"),
+            })),
+            Condition::Known(KnownCondition::EventPropertyIs(EventPropertyIsCondition {
+                key: Cow::Borrowed("content.live"),
+                value: Cow::Owned(SimpleJsonValue::Bool(true)),
+            })),
+        ]),
+        actions: Cow::Borrowed(&[Action::Notify]),
+        default: true,
+        default_enabled: true,
+    },
 ];
 
 lazy_static! {

rust/src/push/evaluator.rs

@@ -637,6 +637,7 @@ fn test_requires_room_version_supports_condition() {
             false,
             false,
             false,
+            false,
         ),
         None,
         None,

rust/src/push/mod.rs

@@ -559,6 +559,7 @@ pub struct FilteredPushRules {
     msc4028_push_encrypted_events: bool,
     msc4210_enabled: bool,
     msc4306_enabled: bool,
+    mscxxxx_beacon_push_rules_enabled: bool,
 }
 
 #[pymethods]
@@ -574,6 +575,7 @@ impl FilteredPushRules {
         msc4028_push_encrypted_events: bool,
         msc4210_enabled: bool,
         msc4306_enabled: bool,
+        mscxxxx_beacon_push_rules_enabled: bool,
     ) -> Self {
         Self {
             push_rules,
@@ -584,6 +586,7 @@ impl FilteredPushRules {
             msc4028_push_encrypted_events,
             msc4210_enabled,
             msc4306_enabled,
+            mscxxxx_beacon_push_rules_enabled,
         }
     }
 
@@ -620,6 +623,12 @@ impl FilteredPushRules {
                     return false;
                 }
 
+                if !self.mscxxxx_beacon_push_rules_enabled
+                    && rule.rule_id.contains("/.io.element.rule.beacon_info")
+                {
+                    return false;
+                }
+
                 if !self.msc4028_push_encrypted_events
                     && rule.rule_id == "global/override/.org.matrix.msc4028.encrypted_event"
                 {

synapse/config/experimental.py

@@ -156,6 +156,13 @@ class ExperimentalConfig(Config):
             "msc3381_polls_enabled", False
         )
 
+        # MSCXXXX (unnumbered draft): default push rules for live location share
+        # beacon_info start events (the MSC3672 state event). Unstable rule ids:
+        # .io.element.rule.beacon_info(_one_to_one).
+        self.mscxxxx_beacon_push_rules_enabled: bool = experimental.get(
+            "mscxxxx_beacon_push_rules_enabled", False
+        )
+
         # MSC3912: Relation-based redactions.
         self.msc3912_enabled: bool = experimental.get("msc3912_enabled", False)
 

synapse/storage/databases/main/push_rule.py

@@ -107,6 +107,7 @@ def _load_rules(
         msc4028_push_encrypted_events=experimental_config.msc4028_push_encrypted_events,
         msc4210_enabled=experimental_config.msc4210_enabled,
         msc4306_enabled=experimental_config.msc4306_enabled,
+        mscxxxx_beacon_push_rules_enabled=experimental_config.mscxxxx_beacon_push_rules_enabled,
     )
 
     return filtered_rules

synapse/synapse_rust/push.pyi

@@ -50,6 +50,7 @@ class FilteredPushRules:
         msc4028_push_encrypted_events: bool,
         msc4210_enabled: bool,
         msc4306_enabled: bool,
+        mscxxxx_beacon_push_rules_enabled: bool,
     ): ...
     def rules(self) -> Collection[tuple[PushRule, bool]]: ...