Fix Suggestion Pattern when text is empty (#1943)

* fix + debounce improvement

* comment

* improved existing function to be more generic

ElementX/Sources/Other/Extensions/Publisher.swift

@@ -25,16 +25,23 @@ extension Publisher where Self.Failure == Never {
     }
 }
 
-extension Publisher where Output == String, Failure == Never {
-    /// Debounce text queries and remove duplicates.
-    /// Clearing the text publishes the update immediately.
-    func debounceAndRemoveDuplicates() -> AnyPublisher<String, Never> {
+extension Publisher where Output: Equatable, Failure == Never {
+    func debounceAndRemoveDuplicates<S: Scheduler>(on scheduler: S, delay: @escaping (Output) -> S.SchedulerTimeType.Stride) -> AnyPublisher<Output, Never> {
         map { query in
-            let milliseconds = query.isEmpty ? 0 : 250
-            return Just(query).delay(for: .milliseconds(milliseconds), scheduler: DispatchQueue.main)
+            Just(query).delay(for: delay(query), scheduler: scheduler)
         }
         .switchToLatest()
         .removeDuplicates()
         .eraseToAnyPublisher()
     }
 }
+
+extension Publisher where Output == String, Failure == Never {
+    /// Debounce text queries and remove duplicates.
+    /// Clearing the text publishes the update immediately.
+    func debounceTextQueriesAndRemoveDuplicates() -> AnyPublisher<String, Never> {
+        debounceAndRemoveDuplicates(on: DispatchQueue.main) { query in
+            query.isEmpty ? .milliseconds(0) : .milliseconds(250)
+        }
+    }
+}

ElementX/Sources/Screens/ComposerToolbar/CompletionSuggestionService.swift

@@ -55,8 +55,10 @@ final class CompletionSuggestionService: CompletionSuggestionServiceProtocol {
                     return membersSuggestion
                 }
             }
-            .debounce(for: 0.5, scheduler: DispatchQueue.main)
-            .eraseToAnyPublisher()
+            // We only debounce if the suggestion is nil
+            .debounceAndRemoveDuplicates(on: DispatchQueue.main) { [weak self] _ in
+                self?.suggestionTriggerSubject.value != nil ? .milliseconds(500) : .milliseconds(0)
+            }
         
         Task {
             switch await roomProxy.canUserTriggerRoomNotification(userID: roomProxy.ownUserID) {
@@ -73,6 +75,10 @@ final class CompletionSuggestionService: CompletionSuggestionServiceProtocol {
     }
     
     private static func isIncluded(searchText: String, userID: String, displayName: String?) -> Bool {
+        // If the search text is empty give back all the results
+        guard !searchText.isEmpty else {
+            return true
+        }
         let containedInUserID = userID.localizedStandardContains(searchText.lowercased())
         
         let containedInDisplayName: Bool

ElementX/Sources/Screens/InviteUsersScreen/InviteUsersScreenViewModel.swift

@@ -95,7 +95,7 @@ class InviteUsersScreenViewModel: InviteUsersScreenViewModelType, InviteUsersScr
     private func setupSubscriptions(selectedUsers: CurrentValuePublisher<[UserProfileProxy], Never>) {
         context.$viewState
             .map(\.bindings.searchQuery)
-            .debounceAndRemoveDuplicates()
+            .debounceTextQueriesAndRemoveDuplicates()
             .sink { [weak self] _ in
                 self?.fetchUsers()
             }

ElementX/Sources/Screens/StartChatScreen/StartChatScreenViewModel.swift

@@ -92,7 +92,7 @@ class StartChatScreenViewModel: StartChatScreenViewModelType, StartChatScreenVie
     private func setupBindings() {
         context.$viewState
             .map(\.bindings.searchQuery)
-            .debounceAndRemoveDuplicates()
+            .debounceTextQueriesAndRemoveDuplicates()
             .sink { [weak self] _ in
                 self?.fetchUsers()
             }

UnitTests/Sources/CompletionSuggestionServiceTests.swift

@@ -87,4 +87,26 @@ final class CompletionSuggestionServiceTests: XCTestCase {
         service.setSuggestionTrigger(.init(type: .user, text: "every"))
         try await deferred.fulfill()
     }
+    
+    func testUserSuggestionsWithEmptyText() async throws {
+        let alice: RoomMemberProxyMock = .mockAlice
+        let bob: RoomMemberProxyMock = .mockBob
+        let members: [RoomMemberProxyMock] = [alice, bob, .mockMe]
+        let roomProxyMock = RoomProxyMock(with: .init(displayName: "test", members: members, canUserTriggerRoomNotification: true))
+        let service = CompletionSuggestionService(roomProxy: roomProxyMock, areSuggestionsEnabled: true)
+                
+        var deferred = deferFulfillment(service.suggestionsPublisher) { suggestions in
+            suggestions == []
+        }
+        
+        try await deferred.fulfill()
+        
+        deferred = deferFulfillment(service.suggestionsPublisher) { suggestions in
+            suggestions == [.user(item: .init(id: alice.userID, displayName: alice.displayName, avatarURL: alice.avatarURL)),
+                            .user(item: .init(id: bob.userID, displayName: bob.displayName, avatarURL: bob.avatarURL)),
+                            .allUsers(item: .allUsersMention(roomAvatar: nil))]
+        }
+        service.setSuggestionTrigger(.init(type: .user, text: ""))
+        try await deferred.fulfill()
+    }
 }