client-api: Allow receiving read receipts for all subscribed rooms in sync::v4

Given "rooms: '*'", the sliding sync proxy will return read receipts for all the subscribed rooms at any
time. This patch adds safe static support for this option, still allowing individual room ids too.

crates/ruma-client-api/src/sync/sync_events/v4.rs

@@ -10,15 +10,15 @@ use js_int::UInt;
 use ruma_common::{
     api::{request, response, Metadata},
     metadata,
-    serde::{duration::opt_ms, Raw},
+    serde::{deserialize_cow_str, duration::opt_ms, Raw},
-    DeviceKeyAlgorithm, MilliSecondsSinceUnixEpoch, OwnedMxcUri, OwnedRoomId,
+    DeviceKeyAlgorithm, MilliSecondsSinceUnixEpoch, OwnedMxcUri, OwnedRoomId, RoomId,
 };
 use ruma_events::{
     receipt::SyncReceiptEvent, typing::SyncTypingEvent, AnyGlobalAccountDataEvent,
     AnyRoomAccountDataEvent, AnyStrippedStateEvent, AnySyncStateEvent, AnySyncTimelineEvent,
     AnyToDeviceEvent, StateEventType, TimelineEventType,
 };
-use serde::{Deserialize, Serialize};
+use serde::{de::Error as _, Deserialize, Serialize};
 
 use super::{DeviceLists, UnreadNotificationsCount};
 
@@ -741,6 +741,42 @@ impl AccountData {
     }
 }
 
+/// Single entry for a room-related read receipt configuration in `ReceiptsConfig`.
+#[derive(Clone, Debug, PartialEq)]
+#[cfg_attr(not(feature = "unstable-exhaustive-types"), non_exhaustive)]
+pub enum RoomReceiptConfig {
+    /// Get read receipts for all the subscribed rooms.
+    AllSubscribed,
+    /// Get read receipts for this particular room.
+    Room(OwnedRoomId),
+}
+
+impl Serialize for RoomReceiptConfig {
+    fn serialize<S>(&self, serializer: S) -> Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        match self {
+            RoomReceiptConfig::AllSubscribed => serializer.serialize_str("*"),
+            RoomReceiptConfig::Room(r) => r.serialize(serializer),
+        }
+    }
+}
+
+impl<'de> Deserialize<'de> for RoomReceiptConfig {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: serde::de::Deserializer<'de>,
+    {
+        match deserialize_cow_str(deserializer)?.as_ref() {
+            "*" => Ok(RoomReceiptConfig::AllSubscribed),
+            other => Ok(RoomReceiptConfig::Room(
+                RoomId::parse(other).map_err(D::Error::custom)?.to_owned(),
+            )),
+        }
+    }
+}
+
 /// Receipt extension configuration.
 ///
 /// According to [MSC3960](https://github.com/matrix-org/matrix-spec-proposals/pull/3960)
@@ -767,7 +803,7 @@ pub struct ReceiptsConfig {
     ///
     /// Sticky.
     #[serde(skip_serializing_if = "Option::is_none")]
-    pub rooms: Option<Vec<OwnedRoomId>>,
+    pub rooms: Option<Vec<RoomReceiptConfig>>,
 }
 
 impl ReceiptsConfig {
@@ -850,3 +886,32 @@ impl Typing {
         self.rooms.is_empty()
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use ruma_common::owned_room_id;
+
+    use crate::sync::sync_events::v4::RoomReceiptConfig;
+
+    #[test]
+    fn serialize_room_receipt_config() {
+        let entry = RoomReceiptConfig::AllSubscribed;
+        assert_eq!(serde_json::to_string(&entry).unwrap().as_str(), r#""*""#);
+
+        let entry = RoomReceiptConfig::Room(owned_room_id!("!n8f893n9:example.com"));
+        assert_eq!(serde_json::to_string(&entry).unwrap().as_str(), r#""!n8f893n9:example.com""#);
+    }
+
+    #[test]
+    fn deserialize_room_receipt_config() {
+        assert_eq!(
+            serde_json::from_str::<RoomReceiptConfig>(r#""*""#).unwrap(),
+            RoomReceiptConfig::AllSubscribed
+        );
+
+        assert_eq!(
+            serde_json::from_str::<RoomReceiptConfig>(r#""!n8f893n9:example.com""#).unwrap(),
+            RoomReceiptConfig::Room(owned_room_id!("!n8f893n9:example.com"))
+        );
+    }
+}