Improve mention suggestion search for large channels

CHANGELOG.md

@@ -5,11 +5,17 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## StreamChat
 ### ✅ Added
+- Add `clearResults()` to user, member, role, and user group search APIs [#4213](https://github.com/GetStream/stream-chat-swift/pull/4213)
+- Add `UserGroupSearchController` for debounced user group search [#4213](https://github.com/GetStream/stream-chat-swift/pull/4213)
+- Add `MemberSearch` for debounced channel member search [#4213](https://github.com/GetStream/stream-chat-swift/pull/4213)
 - Add `ChatMessage.member` with the author's channel role, notification mute state, and member extra data [#4206](https://github.com/GetStream/stream-chat-swift/pull/4206)
 - Add `ChannelSearch` and `ChatChannelSearchController` [#4198](https://github.com/GetStream/stream-chat-swift/pull/4198)
 ### 🐞 Fixed
+- Fix mention suggestions not showing members in channels with 100+ members in the `MentionSuggestionsProvider` [#4213](https://github.com/GetStream/stream-chat-swift/pull/4213)
 - Fix concurrent channel watches hanging indefinitely due to a FetchCache deadlock [#4200](https://github.com/GetStream/stream-chat-swift/pull/4200)
 ### 🔄 Changed
+- Apply dynamic search debouncing to `UserGroupSearch` [#4213](https://github.com/GetStream/stream-chat-swift/pull/4213)
+- Apply dynamic search debouncing to `RoleSearch` and `RoleSearchController` [#4213](https://github.com/GetStream/stream-chat-swift/pull/4213)
 - Apply dynamic search debouncing to message, user, and channel search controllers [#4198](https://github.com/GetStream/stream-chat-swift/pull/4198)
 
 ## StreamChatCommonUI

Sources/StreamChat/Controllers/RoleSearchController/RoleSearchController.swift

@@ -13,7 +13,12 @@ public extension ChatClient {
 
 /// A controller for searching roles.
 ///
+/// Text searches are debounced: 500ms for 1-2 characters, 300ms for 3 or more.
+/// Scheduling a new search cancels any pending debounced work.
+///
 /// Results are replaced on every new search.
+///
+/// - Note: For an async-await alternative, please check ``RoleSearch``.
 public class RoleSearchController: DataController, DelegateCallable, DataStoreProvider, @unchecked Sendable {
     /// The `ChatClient` instance this controller belongs to.
     public let client: ChatClient
@@ -44,13 +49,22 @@ public class RoleSearchController: DataController, DelegateCallable, DataStorePr
     }
 
     private let rolesRepository: RolesRepository
+    private let searchDebouncer: SearchDebouncer
 
-    init(client: ChatClient) {
+    init(
+        client: ChatClient,
+        debouncePolicy: SearchDebouncePolicy = .default
+    ) {
         self.client = client
         rolesRepository = client.rolesRepository
+        searchDebouncer = SearchDebouncer(policy: debouncePolicy)
         super.init()
     }
 
+    deinit {
+        searchDebouncer.cancel()
+    }
+
     /// Searches roles by name.
     ///
     /// The `roles` property is updated with the results on completion.
@@ -74,12 +88,41 @@ public class RoleSearchController: DataController, DelegateCallable, DataStorePr
     ///
     /// The `roles` property is updated with the results on completion.
     ///
+    /// - Note: Searches are debounced on the length of ``RoleSearchQuery/query``.
+    ///
     /// - Parameters:
     ///   - query: The query describing the search term and filters.
     ///   - completion: Called with the matching roles or an error.
     public func searchRoles(
         query: RoleSearchQuery,
         completion: (@MainActor (Result<[Role], Error>) -> Void)? = nil
+    ) {
+        let scheduled = searchDebouncer.schedule(queryLength: query.query.count) { [weak self] in
+            self?.fetch(query, completion: completion)
+        }
+        if !scheduled {
+            callback { [weak self] in
+                completion?(.success(self?.roles ?? []))
+            }
+        }
+    }
+
+    /// Cancels any pending search and clears the current results.
+    public func clearResults() {
+        searchDebouncer.cancel()
+        let previousRoles = roles
+        guard !previousRoles.isEmpty else { return }
+
+        roles = []
+        delegateCallback { [weak self] in
+            guard let self else { return }
+            $0.controller(self, didChangeRoles: self.roles)
+        }
+    }
+
+    private func fetch(
+        _ query: RoleSearchQuery,
+        completion: (@MainActor (Result<[Role], Error>) -> Void)?
     ) {
         rolesRepository.searchRoles(query: query) { [weak self] result in
             guard let self else { return }

Sources/StreamChat/Controllers/UserGroupSearchController/UserGroupSearchController.swift

@@ -0,0 +1,151 @@
+//
+// Copyright © 2026 Stream.io Inc. All rights reserved.
+//
+
+import Foundation
+
+public extension ChatClient {
+    /// Creates a new `UserGroupSearchController`.
+    func userGroupSearchController() -> UserGroupSearchController {
+        .init(client: self)
+    }
+}
+
+/// A controller for searching user groups.
+///
+/// Text searches are debounced: 500ms for 1-2 characters, 300ms for 3 or more.
+/// Scheduling a new search cancels any pending debounced work.
+///
+/// Results are replaced on every new search.
+///
+/// - Note: For an async-await alternative, please check ``UserGroupSearch``.
+public class UserGroupSearchController: DataController, DelegateCallable, DataStoreProvider, @unchecked Sendable {
+    /// The `ChatClient` instance this controller belongs to.
+    public let client: ChatClient
+
+    /// The user groups returned by the last search.
+    public private(set) var userGroups: [UserGroup] = []
+
+    /// Set the delegate of `UserGroupSearchController` to observe changes.
+    public weak var delegate: UserGroupSearchControllerDelegate? {
+        get { multicastDelegate.mainDelegate }
+        set { multicastDelegate.set(mainDelegate: newValue) }
+    }
+
+    var multicastDelegate: MulticastDelegate<UserGroupSearchControllerDelegate> = .init() {
+        didSet {
+            stateMulticastDelegate.set(mainDelegate: multicastDelegate.mainDelegate)
+            stateMulticastDelegate.set(additionalDelegates: multicastDelegate.additionalDelegates)
+        }
+    }
+
+    private let userGroupsRepository: UserGroupsRepository
+    private let searchDebouncer: SearchDebouncer
+
+    init(
+        client: ChatClient,
+        debouncePolicy: SearchDebouncePolicy = .default
+    ) {
+        self.client = client
+        userGroupsRepository = client.userGroupsRepository
+        searchDebouncer = SearchDebouncer(policy: debouncePolicy)
+        super.init()
+    }
+
+    deinit {
+        searchDebouncer.cancel()
+    }
+
+    /// Searches user groups by name.
+    ///
+    /// The `userGroups` property is updated with the results on completion.
+    ///
+    /// - Parameters:
+    ///   - text: The search term used to match group names.
+    ///   - teamId: When set, restricts the search to groups scoped to the given team.
+    ///   - completion: Called with the matching user groups or an error.
+    public func searchUserGroups(
+        text: String,
+        teamId: String? = nil,
+        completion: (@MainActor (Result<[UserGroup], Error>) -> Void)? = nil
+    ) {
+        searchUserGroups(
+            query: UserGroupSearchQuery(query: text, teamId: teamId),
+            completion: completion
+        )
+    }
+
+    /// Searches user groups using the provided query.
+    ///
+    /// The `userGroups` property is updated with the results on completion.
+    ///
+    /// - Note: Searches are debounced on the length of ``UserGroupSearchQuery/query``.
+    ///
+    /// - Parameters:
+    ///   - query: The query describing the search term and filters.
+    ///   - completion: Called with the matching user groups or an error.
+    public func searchUserGroups(
+        query: UserGroupSearchQuery,
+        completion: (@MainActor (Result<[UserGroup], Error>) -> Void)? = nil
+    ) {
+        let scheduled = searchDebouncer.schedule(queryLength: query.query.count) { [weak self] in
+            self?.fetch(query, completion: completion)
+        }
+        if !scheduled {
+            callback { [weak self] in
+                completion?(.success(self?.userGroups ?? []))
+            }
+        }
+    }
+
+    /// Cancels any pending search and clears the current results.
+    public func clearResults() {
+        searchDebouncer.cancel()
+        let previousUserGroups = userGroups
+        guard !previousUserGroups.isEmpty else { return }
+
+        userGroups = []
+        delegateCallback { [weak self] in
+            guard let self else { return }
+            $0.controller(self, didChangeUserGroups: self.userGroups)
+        }
+    }
+
+    private func fetch(
+        _ query: UserGroupSearchQuery,
+        completion: (@MainActor (Result<[UserGroup], Error>) -> Void)?
+    ) {
+        userGroupsRepository.searchUserGroups(query: query) { [weak self] result in
+            guard let self else { return }
+            switch result {
+            case .success(let fetchedUserGroups):
+                self.userGroups = fetchedUserGroups
+                self.state = .remoteDataFetched
+                self.delegateCallback { [weak self] in
+                    guard let self else { return }
+                    $0.controller(self, didChangeUserGroups: self.userGroups)
+                }
+                self.callback { completion?(.success(fetchedUserGroups)) }
+            case .failure(let error):
+                self.state = .remoteDataFetchFailed(ClientError(with: error))
+                self.callback { completion?(.failure(error)) }
+            }
+        }
+    }
+}
+
+/// `UserGroupSearchController` uses this protocol to communicate changes to its delegate.
+public protocol UserGroupSearchControllerDelegate: DataControllerStateDelegate {
+    /// The controller updated its list of user groups.
+    func controller(
+        _ controller: UserGroupSearchController,
+        didChangeUserGroups userGroups: [UserGroup]
+    )
+}
+
+public extension UserGroupSearchControllerDelegate {
+    func controller(
+        _ controller: UserGroupSearchController,
+        didChangeUserGroups userGroups: [UserGroup]
+    ) {}
+}

Sources/StreamChat/MentionSuggestions/DefaultMentionSuggestionsProvider.swift

@@ -9,12 +9,17 @@ import Foundation
 /// Suggests users only, preserving the historical mention behaviour. By default
 /// it searches the channel's members and watchers; pass `mentionAllAppUsers: true`
 /// at initialization to search across all app users instead.
+///
+/// When the channel has more members than are available in
+/// `ChatChannel.lastActiveMembers`, members are searched remotely via
+/// ``MemberSearch``.
 public final class DefaultMentionSuggestionsProvider: MentionSuggestionsProvider, Sendable {
     /// When `true`, user suggestions are searched across all app users instead
     /// of only the channel's members and watchers.
     public let mentionAllAppUsers: Bool
 
     private let userSearch: UserSearch
+    private let memberSearch: MemberSearch
     private let currentUserId: @Sendable () -> UserId?
 
     /// Creates a new default mention suggestions provider.
@@ -25,22 +30,23 @@ public final class DefaultMentionSuggestionsProvider: MentionSuggestionsProvider
     public init(client: ChatClient, mentionAllAppUsers: Bool = false) {
         self.mentionAllAppUsers = mentionAllAppUsers
         userSearch = client.makeUserSearch()
+        memberSearch = client.makeMemberSearch()
         currentUserId = { [weak client] in client?.currentUserId }
     }
 
     public func mentionSuggestions(for request: MentionSuggestionsRequest) async throws -> [MentionSuggestion] {
-        let users: [ChatUser]
-        if mentionAllAppUsers {
-            let query = MentionSuggestionsSearch.allAppUsersQuery(for: request.text)
-            users = try await userSearch.search(query: query)
-        } else {
-            let channel = request.channel
-            users = MentionSuggestionsSearch.searchUsers(
-                channel.lastActiveWatchers.map(\.self) + channel.lastActiveMembers.map(\.self),
-                by: request.text,
-                excludingId: currentUserId()
-            )
-        }
+        let users = try await MentionSuggestionsSearch.fetchUsers(
+            for: request,
+            mentionAllAppUsers: mentionAllAppUsers,
+            currentUserId: currentUserId(),
+            userSearch: userSearch,
+            memberSearch: memberSearch
+        )
         return users.map { MentionSuggestion.user($0) }
     }
+
+    public func clearResults() async {
+        await userSearch.clearResults()
+        await memberSearch.clearResults()
+    }
 }

Sources/StreamChat/MentionSuggestions/EnhancedMentionSuggestionsProvider.swift

@@ -9,6 +9,10 @@ import Foundation
 /// In addition to user mentions, it suggests `@here`, `@channel`, roles and user groups.
 /// Which of these types is suggested is determined by the channel's own
 /// capabilities (`notify-here`, `notify-channel`, `notify-role`, `notify-group`).
+///
+/// When the channel has more members than are available in
+/// `ChatChannel.lastActiveMembers`, members are searched remotely via
+/// ``MemberSearch``.
 public final class EnhancedMentionSuggestionsProvider: MentionSuggestionsProvider, Sendable {
     /// When `true`, user suggestions are searched across all app users instead
     /// of only the channel's members and watchers.
@@ -17,6 +21,7 @@ public final class EnhancedMentionSuggestionsProvider: MentionSuggestionsProvide
     private let userSearch: UserSearch
     private let roleSearch: RoleSearch
     private let userGroupSearch: UserGroupSearch
+    private let memberSearch: MemberSearch
     private let currentUserId: @Sendable () -> UserId?
 
     /// Creates a new enhanced mention suggestions provider.
@@ -29,6 +34,7 @@ public final class EnhancedMentionSuggestionsProvider: MentionSuggestionsProvide
         userSearch = client.makeUserSearch()
         roleSearch = client.makeRoleSearch()
         userGroupSearch = client.makeUserGroupSearch()
+        memberSearch = client.makeMemberSearch()
         currentUserId = { [weak client] in client?.currentUserId }
     }
 
@@ -98,23 +104,25 @@ public final class EnhancedMentionSuggestionsProvider: MentionSuggestionsProvide
     }
 
     private func fetchUsers(for request: MentionSuggestionsRequest) async -> [MentionSuggestion] {
-        let users: [ChatUser]
-        if mentionAllAppUsers {
-            do {
-                let query = MentionSuggestionsSearch.allAppUsersQuery(for: request.text)
-                users = try await userSearch.search(query: query)
-            } catch {
-                log.error("Failed to fetch user suggestions: \(error)")
-                users = []
-            }
-        } else {
-            let channel = request.channel
-            users = MentionSuggestionsSearch.searchUsers(
-                channel.lastActiveWatchers.map(\.self) + channel.lastActiveMembers.map(\.self),
-                by: request.text,
-                excludingId: currentUserId()
+        do {
+            let users = try await MentionSuggestionsSearch.fetchUsers(
+                for: request,
+                mentionAllAppUsers: mentionAllAppUsers,
+                currentUserId: currentUserId(),
+                userSearch: userSearch,
+                memberSearch: memberSearch
             )
+            return users.map { MentionSuggestion.user($0) }
+        } catch {
+            log.error("Failed to fetch user suggestions: \(error)")
+            return []
         }
-        return users.map { MentionSuggestion.user($0) }
+    }
+
+    public func clearResults() async {
+        await userSearch.clearResults()
+        await memberSearch.clearResults()
+        await roleSearch.clearResults()
+        await userGroupSearch.clearResults()
     }
 }

Sources/StreamChat/MentionSuggestions/MentionSuggestionsProvider.swift

@@ -30,6 +30,12 @@ public protocol MentionSuggestionsProvider: Sendable {
     /// - Parameter request: The context describing the current mention query.
     /// - Returns: The suggestions to present, in display order.
     func mentionSuggestions(for request: MentionSuggestionsRequest) async throws -> [MentionSuggestion]
+
+    /// Cancels any pending or in-flight suggestion searches and clears cached results.
+    ///
+    /// Call this when the mention query ends (for example when the user deletes `@`)
+    /// so a slower, superseded search cannot surface stale suggestions.
+    func clearResults() async
 }
 
 public extension MentionSuggestionsProvider {
@@ -55,4 +61,6 @@ public extension MentionSuggestionsProvider {
             }
         }
     }
+
+    func clearResults() async {}
 }