feat: Add support for MSC4171

Introduce support for MSC4171, enabling the designation of certain users
as service members. These flagged users are excluded from the room
display name calculation.

MSC: matrix-org/matrix-spec-proposals#4171

Cargo.toml

@@ -18,7 +18,7 @@ default-members = ["benchmarks", "crates/*", "labs/*"]
 resolver = "2"
 
 [workspace.package]
-rust-version = "1.80"
+rust-version = "1.82"
 
 [workspace.dependencies]
 anyhow = "1.0.93"
@@ -56,7 +56,7 @@ proptest = { version = "1.5.0", default-features = false, features = ["std"] }
 rand = "0.8.5"
 reqwest = { version = "0.12.4", default-features = false }
 rmp-serde = "1.3.0"
-ruma = { git = "https://github.com/ruma/ruma.git", rev = "35fda7f2f7811156df2e60b223dbf136fc143bc8", features = [
+ruma = { git = "https://github.com/ruma/ruma", rev = "c91499fc464adc865a7c99d0ce0b35982ad96711", features = [
     "client-api-c",
     "compat-upload-signatures",
     "compat-user-id",
@@ -69,8 +69,9 @@ ruma = { git = "https://github.com/ruma/ruma.git", rev = "35fda7f2f7811156df2e60
     "unstable-msc3489",
     "unstable-msc4075",
     "unstable-msc4140",
+    "unstable-msc4171",
 ] }
-ruma-common = { git = "https://github.com/ruma/ruma.git", rev = "35fda7f2f7811156df2e60b223dbf136fc143bc8" }
+ruma-common = { git = "https://github.com/ruma/ruma", rev = "c91499fc464adc865a7c99d0ce0b35982ad96711" }
 serde = "1.0.151"
 serde_html_form = "0.2.0"
 serde_json = "1.0.91"

crates/matrix-sdk-base/CHANGELOG.md

@@ -6,6 +6,14 @@ All notable changes to this project will be documented in this file.
 
 ## [Unreleased] - ReleaseDate
 
+### Features
+
+- Introduced support for
+  [MSC4171](https://github.com/matrix-org/matrix-rust-sdk/pull/4335), enabling
+  the designation of certain users as service members. These flagged users are
+  excluded from the room display name calculation.
+  ([#4335](https://github.com/matrix-org/matrix-rust-sdk/pull/4335))
+
 ### Bug Fixes
 
 - Fix an off-by-one error in the `ObservableMap` when the `remove()` method is

crates/matrix-sdk-base/src/rooms/normal.rs

@@ -20,6 +20,7 @@ use std::{
     sync::{atomic::AtomicBool, Arc},
 };
 
+use as_variant::as_variant;
 use bitflags::bitflags;
 use eyeball::{SharedObservable, Subscriber};
 use futures_util::{Stream, StreamExt};
@@ -35,6 +36,7 @@ use ruma::{
         call::member::{CallMemberStateKey, MembershipData},
         direct::OwnedDirectUserIdentifier,
         ignored_user_list::IgnoredUserListEventContent,
+        member_hints::MemberHintsEventContent,
         receipt::{Receipt, ReceiptThread, ReceiptType},
         room::{
             avatar::{self, RoomAvatarEventContent},
@@ -50,7 +52,7 @@ use ruma::{
         },
         tag::{TagEventContent, Tags},
         AnyRoomAccountDataEvent, AnyStrippedStateEvent, AnySyncStateEvent,
-        RoomAccountDataEventType,
+        RoomAccountDataEventType, SyncStateEvent,
     },
     room::RoomType,
     serde::Raw,
@@ -59,7 +61,7 @@ use ruma::{
 };
 use serde::{Deserialize, Serialize};
 use tokio::sync::broadcast;
-use tracing::{debug, field::debug, info, instrument, warn};
+use tracing::{debug, field::debug, info, instrument, trace, warn};
 
 use super::{
     members::MemberRoomInfo, BaseRoomInfo, RoomCreateWithCreatorEventContent, RoomDisplayName,
@@ -68,7 +70,9 @@ use super::{
 #[cfg(feature = "experimental-sliding-sync")]
 use crate::latest_event::LatestEvent;
 use crate::{
-    deserialized_responses::{DisplayName, MemberEvent, RawSyncOrStrippedState},
+    deserialized_responses::{
+        DisplayName, MemberEvent, RawSyncOrStrippedState, SyncOrStrippedState,
+    },
     notification_settings::RoomNotificationMode,
     read_receipts::RoomReadReceipts,
     store::{DynStateStore, Result as StoreResult, StateStoreExt},
@@ -222,6 +226,18 @@ impl From<&MembershipState> for RoomState {
 /// try to behave similarly here.
 const NUM_HEROES: usize = 5;
 
+/// A filter to remove our own user and the users specified in the member hints
+/// state event, so called service members, from the list of heroes.
+///
+/// The heroes will then be used to calculate a display name for the room if one
+/// wasn't explicitly defined.
+fn heroes_filter<'a>(
+    own_user_id: &'a UserId,
+    member_hints: &'a MemberHintsEventContent,
+) -> impl Fn(&UserId) -> bool + use<'a> {
+    move |user_id| user_id != own_user_id && !member_hints.service_members.contains(user_id)
+}
+
 impl Room {
     /// The size of the latest_encrypted_events RingBuffer
     // SAFETY: `new_unchecked` is safe because 10 is not zero.
@@ -678,12 +694,16 @@ impl Room {
     ///
     /// Returns the display names as a list of strings.
     async fn extract_heroes(&self, heroes: &[RoomHero]) -> StoreResult<Vec<String>> {
-        let own_user_id = self.own_user_id().as_str();
-
         let mut names = Vec::with_capacity(heroes.len());
-        let heroes = heroes.iter().filter(|hero| hero.user_id != own_user_id);
+        let own_user_id = self.own_user_id();
+        let member_hints = self.get_member_hints().await?;
+
+        // Construct a filter that is specific to this own user id, set of member hints,
+        // and accepts a `RoomHero` type.
+        let heroes_filter = heroes_filter(own_user_id, &member_hints);
+        let heroes_filter = |hero: &&RoomHero| heroes_filter(&hero.user_id);
 
-        for hero in heroes {
+        for hero in heroes.iter().filter(heroes_filter) {
             if let Some(display_name) = &hero.display_name {
                 names.push(display_name.clone());
             } else {
@@ -710,12 +730,30 @@ impl Room {
     ///
     /// Returns a `(heroes_names, num_joined_invited)` tuple.
     async fn compute_summary(&self) -> StoreResult<(Vec<String>, u64)> {
+        let member_hints = self.get_member_hints().await?;
+
+        // Construct a filter that is specific to this own user id, set of member hints,
+        // and accepts a `RoomMember` type.
+        let heroes_filter = heroes_filter(&self.own_user_id, &member_hints);
+        let heroes_filter = |u: &RoomMember| heroes_filter(u.user_id());
+
         let mut members = self.members(RoomMemberships::JOIN | RoomMemberships::INVITE).await?;
 
+        // If we have some service members, they shouldn't count to the number of
+        // joined/invited members, otherwise we'll wrongly assume that there are more
+        // members in the room than they are for the "Bob and 2 others" case.
+        let num_service_members = members
+            .iter()
+            .filter(|member| member_hints.service_members.contains(member.user_id()))
+            .count();
+
         // We can make a good prediction of the total number of joined and invited
         // members here. This might be incorrect if the database info is
         // outdated.
-        let num_joined_invited = members.len() as u64;
+        //
+        // Note: Subtracting here is fine because `num_service_members` is a subset of
+        // `members.len()` due to the above filter operation.
+        let num_joined_invited = members.len() - num_service_members;
 
         if num_joined_invited == 0
             || (num_joined_invited == 1 && members[0].user_id() == self.own_user_id)
@@ -729,12 +767,34 @@ impl Room {
 
         let heroes = members
             .into_iter()
-            .filter(|u| u.user_id() != self.own_user_id)
+            .filter(heroes_filter)
             .take(NUM_HEROES)
             .map(|u| u.name().to_owned())
             .collect();
 
-        Ok((heroes, num_joined_invited))
+        trace!(
+            ?heroes,
+            num_joined_invited,
+            num_service_members,
+            "Computed a room summary since we didn't receive one."
+        );
+
+        Ok((heroes, num_joined_invited as u64))
+    }
+
+    async fn get_member_hints(&self) -> StoreResult<MemberHintsEventContent> {
+        Ok(self
+            .store
+            .get_state_event_static::<MemberHintsEventContent>(self.room_id())
+            .await?
+            .and_then(|event| {
+                event
+                    .deserialize()
+                    .inspect_err(|e| warn!("Couldn't deserialize the member hints event: {e}"))
+                    .ok()
+            })
+            .and_then(|event| as_variant!(event, SyncOrStrippedState::Sync(SyncStateEvent::Original(e)) => e.content))
+            .unwrap_or_default())
     }
 
     /// Returns the cached computed display name, if available.
@@ -1854,6 +1914,7 @@ fn compute_display_name_from_heroes(
 #[cfg(test)]
 mod tests {
     use std::{
+        collections::BTreeSet,
         ops::{Not, Sub},
         str::FromStr,
         sync::Arc,
@@ -1894,6 +1955,7 @@ mod tests {
         OwnedEventId, OwnedUserId, UserId,
     };
     use serde_json::json;
+    use similar_asserts::assert_eq;
     use stream_assert::{assert_pending, assert_ready};
 
     use super::{compute_display_name_from_heroes, Room, RoomHero, RoomInfo, RoomState, SyncInfo};
@@ -2546,6 +2608,53 @@ mod tests {
         );
     }
 
+    #[async_test]
+    async fn test_display_name_dm_joined_service_members() {
+        let (store, room) = make_room_test_helper(RoomState::Joined);
+        let room_id = room_id!("!test:localhost");
+
+        let matthew = user_id!("@sahasrhala:example.org");
+        let me = user_id!("@me:example.org");
+        let bot = user_id!("@bot:example.org");
+
+        let mut changes = StateChanges::new("".to_owned());
+        let summary = assign!(RumaSummary::new(), {
+            joined_member_count: Some(2u32.into()),
+            heroes: vec![me.to_owned(), matthew.to_owned(), bot.to_owned()],
+        });
+
+        let f = EventFactory::new().room(room_id!("!test:localhost"));
+
+        let members = changes
+            .state
+            .entry(room_id.to_owned())
+            .or_default()
+            .entry(StateEventType::RoomMember)
+            .or_default();
+        members.insert(matthew.into(), f.member(matthew).display_name("Matthew").into_raw());
+        members.insert(me.into(), f.member(me).display_name("Me").into_raw());
+        members.insert(bot.into(), f.member(bot).display_name("Bot").into_raw());
+
+        let member_hints_content =
+            f.member_hints(BTreeSet::from([bot.to_owned()])).sender(me).into_raw();
+        changes
+            .state
+            .entry(room_id.to_owned())
+            .or_default()
+            .entry(StateEventType::MemberHints)
+            .or_default()
+            .insert("".to_owned(), member_hints_content);
+
+        store.save_changes(&changes).await.unwrap();
+
+        room.inner.update_if(|info| info.update_from_ruma_summary(&summary));
+        // Bot should not contribute to the display name.
+        assert_eq!(
+            room.compute_display_name().await.unwrap(),
+            RoomDisplayName::Calculated("Matthew".to_owned())
+        );
+    }
+
     #[async_test]
     async fn test_display_name_dm_joined_no_heroes() {
         let (store, room) = make_room_test_helper(RoomState::Joined);
@@ -2573,6 +2682,47 @@ mod tests {
         );
     }
 
+    #[async_test]
+    async fn test_display_name_dm_joined_no_heroes_service_members() {
+        let (store, room) = make_room_test_helper(RoomState::Joined);
+        let room_id = room_id!("!test:localhost");
+
+        let matthew = user_id!("@matthew:example.org");
+        let me = user_id!("@me:example.org");
+        let bot = user_id!("@bot:example.org");
+
+        let mut changes = StateChanges::new("".to_owned());
+
+        let f = EventFactory::new().room(room_id!("!test:localhost"));
+
+        let members = changes
+            .state
+            .entry(room_id.to_owned())
+            .or_default()
+            .entry(StateEventType::RoomMember)
+            .or_default();
+        members.insert(matthew.into(), f.member(matthew).display_name("Matthew").into_raw());
+        members.insert(me.into(), f.member(me).display_name("Me").into_raw());
+        members.insert(bot.into(), f.member(bot).display_name("Bot").into_raw());
+
+        let member_hints_content =
+            f.member_hints(BTreeSet::from([bot.to_owned()])).sender(me).into_raw();
+        changes
+            .state
+            .entry(room_id.to_owned())
+            .or_default()
+            .entry(StateEventType::MemberHints)
+            .or_default()
+            .insert("".to_owned(), member_hints_content);
+
+        store.save_changes(&changes).await.unwrap();
+
+        assert_eq!(
+            room.compute_display_name().await.unwrap(),
+            RoomDisplayName::Calculated("Matthew".to_owned())
+        );
+    }
+
     #[async_test]
     async fn test_display_name_deterministic() {
         let (store, room) = make_room_test_helper(RoomState::Joined);