Fix updating channel's preview message when coming back to online

CHANGELOG.md

@@ -3,7 +3,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 # Upcoming
 
-### 🔄 Changed
+## StreamChat
+### 🐞 Fixed
+- Update channel's preview message when coming back to online [#3574](https://github.com/GetStream/stream-chat-swift/pull/3574)
 
 # [4.71.0](https://github.com/GetStream/stream-chat-swift/releases/tag/4.71.0)
 _January 28, 2025_

Sources/StreamChat/Utils/Database/NSManagedObject+Extensions.swift

@@ -179,7 +179,15 @@ class FetchCache {
 
 extension NSManagedObjectContext {
     func fetch<T>(_ request: NSFetchRequest<T>, using cache: FetchCache) throws -> [T] where T: NSFetchRequestResult {
-        if let objectIds = cache.get(request), !objectIds.contains(where: { $0.isTemporaryID }) {
+        func canUseCachedIds(_ objectIds: [NSManagedObjectID]) -> Bool {
+            // Ignore cache when inserted (but not yet saved) object id is present
+            guard !objectIds.contains(where: { $0.isTemporaryID }) else { return false }
+            // Context has pending inserted or deleted objects of this type (can affect ids returned by the fetch request)
+            guard !insertedObjects.contains(where: { $0 is T }) && !deletedObjects.contains(where: { $0 is T }) else { return false }
+            return true
+        }
+
+        if let objectIds = cache.get(request), canUseCachedIds(objectIds) {
             return try objectIds.compactMap { try existingObject(with: $0) as? T }
         }
 

Tests/StreamChatTests/Database/FetchCache_Tests.swift

@@ -56,6 +56,27 @@ final class FetchCache_Tests: XCTestCase {
 
         XCTAssertEqual(cache.cacheEntriesCount, 3)
     }
+
+    func test_ignoringCacheIfContextHasInsertedOrDeletedObjectsOfThatType() async throws {
+        let database = DatabaseContainer(kind: .inMemory, chatClientConfig: .init(apiKeyString: .unique))
+        let cid = ChannelId.unique
+        try database.createCurrentUser(id: .unique, name: "")
+        try database.createChannel(cid: cid, withMessages: true)
+        try await database.write { session in
+            // FetchCache caches the response
+            guard let firstPreviewMessage = session.preview(for: cid) else { throw ClientError.Unknown("Preview message missing") }
+
+            // Insert a new message what is newer than the current preview message
+            let newMessagePayload = MessagePayload.dummy(createdAt: firstPreviewMessage.createdAt.bridgeDate.addingTimeInterval(1.0))
+            try session.saveMessage(payload: newMessagePayload, for: cid, syncOwnReactions: false, cache: nil)
+
+            guard let secondPreviewMessage = session.preview(for: cid) else { throw ClientError.Unknown("Preview message missing") }
+            XCTAssertEqual(newMessagePayload.id, secondPreviewMessage.id)
+            XCTAssertNotEqual(firstPreviewMessage.id, secondPreviewMessage.id)
+        }
+    }
+
+    // MARK: - Test Data
 
     private var tenIds: [TestId] {
         (1...10).map { _ in TestId() }