implement MSC4267 automatically forgetting room on leave

Signed-off-by: strawberry <june@girlboss.ceo>

Author: x86pup

conduwuit-example.toml

@@ -445,10 +445,19 @@
 #
 #allow_federation = true
 
-# This item is undocumented. Please contribute documentation for it.
+# Allows federation requests to be made to itself
+#
+# This isn't intended and is very likely a bug if federation requests are
+# being sent to yourself. This currently mainly exists for development
+# purposes.
 #
 #federation_loopback = false
 
+# Always calls /forget on behalf of the user if leaving a room. This is a
+# part of MSC4267 "Automatically forgetting rooms on leave"
+#
+#forget_forced_upon_leave = false
+
 # Set this to true to require authentication on the normally
 # unauthenticated profile retrieval endpoints (GET)
 # "/_matrix/client/v3/profile/{userId}".

src/api/client/capabilities.rs

@@ -42,5 +42,12 @@ pub(crate) async fn get_capabilities_route(
 		.set("uk.tcpip.msc4133.profile_fields", json!({"enabled": true}))
 		.expect("this is valid JSON we created");
 
+	capabilities
+		.set(
+			"org.matrix.msc4267.forget_forced_upon_leave",
+			json!({"enabled": services.config.forget_forced_upon_leave}),
+		)
+		.expect("valid JSON we created");
+
 	Ok(get_capabilities::v3::Response { capabilities })
 }

src/core/config/mod.rs

@@ -558,9 +558,19 @@ pub struct Config {
 	#[serde(default = "true_fn")]
 	pub allow_federation: bool,
 
+	/// Allows federation requests to be made to itself
+	///
+	/// This isn't intended and is very likely a bug if federation requests are
+	/// being sent to yourself. This currently mainly exists for development
+	/// purposes.
 	#[serde(default)]
 	pub federation_loopback: bool,
 
+	/// Always calls /forget on behalf of the user if leaving a room. This is a
+	/// part of MSC4267 "Automatically forgetting rooms on leave"
+	#[serde(default)]
+	pub forget_forced_upon_leave: bool,
+
 	/// Set this to true to require authentication on the normally
 	/// unauthenticated profile retrieval endpoints (GET)
 	/// "/_matrix/client/v3/profile/{userId}".

src/service/rooms/state_cache/mod.rs

@@ -28,7 +28,7 @@ use ruma::{
 	serde::Raw,
 };
 
-use crate::{Dep, account_data, appservice::RegistrationInfo, globals, rooms, users};
+use crate::{Dep, account_data, appservice::RegistrationInfo, config, globals, rooms, users};
 
 pub struct Service {
 	appservice_in_room_cache: AppServiceInRoomCache,
@@ -38,6 +38,7 @@ pub struct Service {
 
 struct Services {
 	account_data: Dep<account_data::Service>,
+	config: Dep<config::Service>,
 	globals: Dep<globals::Service>,
 	state_accessor: Dep<rooms::state_accessor::Service>,
 	users: Dep<users::Service>,
@@ -70,6 +71,7 @@ impl crate::Service for Service {
 			appservice_in_room_cache: RwLock::new(HashMap::new()),
 			services: Services {
 				account_data: args.depend::<account_data::Service>("account_data"),
+				config: args.depend::<config::Service>("config"),
 				globals: args.depend::<globals::Service>("globals"),
 				state_accessor: args
 					.depend::<rooms::state_accessor::Service>("rooms::state_accessor"),
@@ -268,7 +270,9 @@ impl Service {
 			| MembershipState::Leave | MembershipState::Ban => {
 				self.mark_as_left(user_id, room_id);
 
-				if self.services.globals.user_is_local(user_id) {
+				if self.services.globals.user_is_local(user_id)
+					&& self.services.config.forget_forced_upon_leave
+				{
 					self.forget(room_id, user_id);
 				}
 			},