Refresh the room members when a mention is started (#7438)

* Refresh the room members when a mention is started

The mention suggestions read room.membersStateFlow, which is a cache filled
only by an explicit updateMembers() call. Nothing calls it while a room is
open, so a member who joined after the room was opened never appears in the
suggestion list until the room is left and entered again.

Call updateMembers() when a mention search starts. The trigger is
distinctUntilChanged on "the current suggestion is a mention", so it fires
once per mention rather than on every keystroke, and fetchRoomMembers already
no-ops while a fetch is in flight.

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/messagecomposer/MessageComposerPresenter.kt

@@ -86,6 +86,7 @@ import io.element.android.libraries.textcomposer.model.MarkdownTextEditorState
 import io.element.android.libraries.textcomposer.model.Message
 import io.element.android.libraries.textcomposer.model.MessageComposerMode
 import io.element.android.libraries.textcomposer.model.Suggestion
+import io.element.android.libraries.textcomposer.model.SuggestionType
 import io.element.android.libraries.textcomposer.model.TextEditorState
 import io.element.android.libraries.textcomposer.model.rememberMarkdownTextEditorState
 import io.element.android.services.analytics.api.AnalyticsService
@@ -103,7 +104,9 @@ import kotlinx.coroutines.flow.SharingStarted
 import kotlinx.coroutines.flow.collect
 import kotlinx.coroutines.flow.combine
 import kotlinx.coroutines.flow.debounce
+import kotlinx.coroutines.flow.distinctUntilChangedBy
 import kotlinx.coroutines.flow.filter
+import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.merge
 import kotlinx.coroutines.flow.stateIn
 import kotlinx.coroutines.launch
@@ -459,6 +462,14 @@ class MessageComposerPresenter(
 
             val mentionTriggerFlow = merge(mentionStartTrigger, mentionCompletionTrigger)
 
+            // Refresh the room members, which are only loaded on demand, when a mention starts
+            launch {
+                suggestionSearchTrigger
+                    .distinctUntilChangedBy { it?.type }
+                    .filter { it?.type == SuggestionType.Mention }
+                    .collect { room.updateMembers() }
+            }
+
             val roomAliasSuggestionsFlow = roomAliasSuggestionsDataSource
                 .getAllRoomAliasSuggestions()
                 .stateIn(this, SharingStarted.Lazily, emptyList())

features/messages/impl/src/test/kotlin/io/element/android/features/messages/impl/messagecomposer/MessageComposerPresenterTest.kt

@@ -1056,7 +1056,8 @@ class MessageComposerPresenterTest : RobolectricTest() {
             baseRoom = FakeBaseRoom(
                 roomPermissions = FakeRoomPermissions(
                     canTriggerRoomNotification = true,
-                )
+                ),
+                updateMembersResult = {},
             ),
             typingNoticeResult = { Result.success(Unit) }
         ).apply {
@@ -1103,6 +1104,55 @@ class MessageComposerPresenterTest : RobolectricTest() {
         }
     }
 
+    @Test
+    fun `present - mention suggestions refresh the room members`() = runTest {
+        val currentUser = aRoomMember(userId = A_USER_ID, membership = RoomMembershipState.JOIN)
+        val bob = aRoomMember(userId = A_USER_ID_2, membership = RoomMembershipState.JOIN)
+        val updateMembersResult = lambdaRecorder<Unit> { }
+        val room = FakeJoinedRoom(
+            baseRoom = FakeBaseRoom(
+                roomPermissions = FakeRoomPermissions(
+                    canTriggerRoomNotification = true,
+                ),
+                updateMembersResult = updateMembersResult,
+            ),
+            typingNoticeResult = { Result.success(Unit) }
+        ).apply {
+            givenRoomMembersState(
+                RoomMembersState.Ready(
+                    persistentListOf(currentUser, bob),
+                )
+            )
+            givenRoomInfo(aRoomInfo(isDirect = false))
+        }
+        val presenter = createPresenter(
+            room = room,
+            slashCommandService = FakeSlashCommandService(
+                getSuggestionsResult = { _, _ -> emptyList() },
+            ),
+        )
+        presenter.test {
+            val initialState = awaitItem()
+            initialState.eventSink(MessageComposerEvent.SuggestionReceived(Suggestion(0, 0, SuggestionType.Mention, "")))
+            skipItems(1)
+            assertThat(awaitItem().suggestions).containsExactly(ResolvedSuggestion.AtRoom, ResolvedSuggestion.Member(bob))
+            updateMembersResult.assertions().isCalledOnce()
+
+            // Typing after the `@` must not refresh the members again
+            initialState.eventSink(MessageComposerEvent.SuggestionReceived(Suggestion(0, 1, SuggestionType.Mention, "b")))
+            initialState.eventSink(MessageComposerEvent.SuggestionReceived(Suggestion(0, 2, SuggestionType.Mention, "bo")))
+            advanceUntilIdle()
+            updateMembersResult.assertions().isCalledOnce()
+
+            // Starting a new mention refreshes them again
+            initialState.eventSink(MessageComposerEvent.SuggestionReceived(null))
+            initialState.eventSink(MessageComposerEvent.SuggestionReceived(Suggestion(0, 0, SuggestionType.Mention, "")))
+            advanceUntilIdle()
+            updateMembersResult.assertions().isCalledExactly(2)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
     @Test
     fun `present - room mention suggestions no permission`() = runTest {
         val currentUser = aRoomMember(userId = A_USER_ID, membership = RoomMembershipState.JOIN)
@@ -1113,7 +1163,8 @@ class MessageComposerPresenterTest : RobolectricTest() {
             baseRoom = FakeBaseRoom(
                 roomPermissions = FakeRoomPermissions(
                     canTriggerRoomNotification = false,
-                )
+                ),
+                updateMembersResult = {},
             ),
             typingNoticeResult = { Result.success(Unit) }
         ).apply {
@@ -1144,6 +1195,7 @@ class MessageComposerPresenterTest : RobolectricTest() {
         val room = FakeJoinedRoom(
             baseRoom = FakeBaseRoom(
                 roomPermissions = FakeRoomPermissions(canTriggerRoomNotification = true),
+                updateMembersResult = {},
             ),
             typingNoticeResult = { Result.success(Unit) }
         ).apply {