From 2a235d8ea670b68c7484beb2e703dd6da638ecdf Mon Sep 17 00:00:00 2001
From: Benjamin Bouvier <public@benj.me>
Date: Mon, 25 Sep 2023 17:17:35 +0200
Subject: [PATCH] fix: signal that a concurrent request failed to the caller,
 instead of assuming it succeeded

---
 crates/matrix-sdk/src/client/mod.rs |  2 +-
 crates/matrix-sdk/src/error.rs      |  4 ++++
 crates/matrix-sdk/src/room/mod.rs   | 13 +++++++------
 3 files changed, 12 insertions(+), 7 deletions(-)

diff --git a/crates/matrix-sdk/src/client/mod.rs b/crates/matrix-sdk/src/client/mod.rs
index 61e74a2c9..bc7beacc2 100644
--- a/crates/matrix-sdk/src/client/mod.rs
+++ b/crates/matrix-sdk/src/client/mod.rs
@@ -165,7 +165,7 @@ pub(crate) struct ClientInner {
     pub(crate) key_claim_lock: Mutex<()>,
     /// Lock to ensure that only one members request is running at a time, per
     /// room.
-    pub(crate) members_request_locks: Mutex<BTreeMap<OwnedRoomId, Arc<Mutex<()>>>>,
+    pub(crate) members_request_locks: Mutex<BTreeMap<OwnedRoomId, Arc<Mutex<Result<(), ()>>>>>,
     /// Locks for requests on the encryption state of rooms.
     pub(crate) encryption_state_request_locks: Mutex<BTreeMap<OwnedRoomId, Arc<Mutex<()>>>>,
     pub(crate) typing_notice_times: DashMap<OwnedRoomId, Instant>,
diff --git a/crates/matrix-sdk/src/error.rs b/crates/matrix-sdk/src/error.rs
index ed457ec3f..d2a87392f 100644
--- a/crates/matrix-sdk/src/error.rs
+++ b/crates/matrix-sdk/src/error.rs
@@ -266,6 +266,10 @@ pub enum Error {
     #[error(transparent)]
     Oidc(#[from] crate::oidc::OidcError),
 
+    /// A concurrent request to a deduplicated request has failed.
+    #[error("a concurrent request failed; see logs for details")]
+    ConcurrentRequestFailed,
+
     /// An other error was raised
     /// this might happen because encryption was enabled on the base-crate
     /// but not here and that raised.
diff --git a/crates/matrix-sdk/src/room/mod.rs b/crates/matrix-sdk/src/room/mod.rs
index 1a3e63eb0..564d9719f 100644
--- a/crates/matrix-sdk/src/room/mod.rs
+++ b/crates/matrix-sdk/src/room/mod.rs
@@ -388,14 +388,12 @@ impl Room {
             // If a member request is already going on, await the release of
             // the lock.
             drop(map);
-            _ = mutex.lock().await;
-
-            Ok(None)
+            return mutex.lock().await.map(|()| None).map_err(|()| Error::ConcurrentRequestFailed);
         } else {
-            let mutex = Arc::new(Mutex::new(()));
-            map.insert(self.inner.room_id().to_owned(), mutex.clone());
+            let request_mutex = Arc::new(Mutex::new(Ok(())));
+            map.insert(self.inner.room_id().to_owned(), request_mutex.clone());
 
-            let _guard = mutex.lock().await;
+            let mut request_guard = request_mutex.lock().await;
             drop(map);
 
             let request = get_member_events::v3::Request::new(self.inner.room_id().to_owned());
@@ -420,6 +418,9 @@ impl Room {
                 }
 
                 Err(err) => {
+                    // Mark the request as failed.
+                    *request_guard = Err(());
+
                     // Remove the request from the in-flights set.
                     self.client
                         .inner