Reload room member list when active members count changes (#5129)

features/roomdetails/impl/src/main/kotlin/io/element/android/features/roomdetails/impl/members/RoomMemberListPresenter.kt

@@ -38,8 +38,10 @@ import kotlinx.collections.immutable.ImmutableMap
 import kotlinx.collections.immutable.persistentMapOf
 import kotlinx.collections.immutable.toImmutableList
 import kotlinx.collections.immutable.toPersistentMap
+import kotlinx.coroutines.flow.distinctUntilChanged
 import kotlinx.coroutines.flow.first
 import kotlinx.coroutines.flow.launchIn
+import kotlinx.coroutines.flow.map
 import kotlinx.coroutines.flow.onEach
 import kotlinx.coroutines.withContext
 import javax.inject.Inject
@@ -64,6 +66,11 @@ class RoomMemberListPresenter @Inject constructor(
         val syncUpdateFlow = room.syncUpdateFlow.collectAsState()
         val canInvite by room.canInviteAsState(syncUpdateFlow.value)
         val roomModerationState = roomMembersModerationPresenter.present()
+        val activeRoomMemberCount by produceState(0L) {
+            room.roomInfoFlow.map { it.activeMembersCount }
+                .distinctUntilChanged()
+                .collect { value = it }
+        }
 
         val roomMemberIdentityStates by produceState(persistentMapOf<UserId, IdentityState>()) {
             room.roomMemberIdentityStateChange(waitForEncryption = true)
@@ -73,8 +80,8 @@ class RoomMemberListPresenter @Inject constructor(
                 .launchIn(this)
         }
 
-        // Ensure we load the latest data when entering this screen
-        LaunchedEffect(Unit) {
+        // Update the room members when the screen is loaded or the active member count changes
+        LaunchedEffect(activeRoomMemberCount) {
             room.updateMembers()
         }
 

features/roomdetails/impl/src/test/kotlin/io/element/android/features/roomdetails/impl/members/RoomMemberListPresenterTest.kt

@@ -23,12 +23,20 @@ import io.element.android.libraries.matrix.test.room.FakeBaseRoom
 import io.element.android.libraries.matrix.test.room.FakeJoinedRoom
 import io.element.android.libraries.matrix.test.room.aRoomInfo
 import io.element.android.tests.testutils.WarmUpRule
+import io.element.android.tests.testutils.lambda.lambdaRecorder
 import io.element.android.tests.testutils.testCoroutineDispatchers
+import kotlinx.collections.immutable.persistentListOf
 import kotlinx.coroutines.ExperimentalCoroutinesApi
+import kotlinx.coroutines.launch
+import kotlinx.coroutines.sync.Mutex
+import kotlinx.coroutines.sync.withLock
 import kotlinx.coroutines.test.TestScope
 import kotlinx.coroutines.test.runTest
+import kotlinx.coroutines.time.withTimeout
+import kotlinx.coroutines.withTimeout
 import org.junit.Rule
 import org.junit.Test
+import kotlin.time.Duration.Companion.seconds
 
 @ExperimentalCoroutinesApi
 class RoomMemberListPresenterTest {
@@ -67,6 +75,59 @@ class RoomMemberListPresenterTest {
         }
     }
 
+    @Test
+    fun `member loading is done automatically when RoomInfo's activeMemberCount changes`() = runTest {
+        val reloadMembersMutex = Mutex()
+        val updateMembersLambda = lambdaRecorder<Unit> {
+            if (reloadMembersMutex.isLocked) {
+                reloadMembersMutex.unlock()
+            }
+        }
+        val room = FakeJoinedRoom(
+            baseRoom = FakeBaseRoom(
+                updateMembersResult = updateMembersLambda,
+                canInviteResult = { Result.success(true) }
+            ).apply {
+                // Needed to avoid discarding the loaded members as a partial and invalid result
+                givenRoomInfo(aRoomInfo(joinedMembersCount = 2))
+            }
+        )
+        val presenter = createPresenter(joinedRoom = room)
+        moleculeFlow(RecompositionMode.Immediate) {
+            presenter.present()
+        }.test {
+            skipItems(1)
+            val initialState = awaitItem()
+            assertThat(initialState.roomMembers.isLoading()).isTrue()
+            room.givenRoomMembersState(RoomMembersState.Ready(aRoomMemberList()))
+            // Skip item while the new members state is processed
+            skipItems(1)
+            val loadedMembersState = awaitItem()
+            assertThat(loadedMembersState.roomMembers.isLoading()).isFalse()
+            assertThat(loadedMembersState.roomMembers.dataOrNull()?.joined).isNotEmpty()
+
+            // Assert no events are emitted only with that change
+            expectNoEvents()
+
+            // This will only progress if the `Room.updateMembers()` function is called, triggered by the RoomInfo change
+            withTimeout(10.seconds) {
+                reloadMembersMutex.withLock {
+                    launch { room.givenRoomInfo(aRoomInfo(activeMembersCount = 0L)) }
+                }
+            }
+
+            // Wait for the update to be processed
+            skipItems(1)
+
+            // Update the room members state as `Room.updateMembers()` would have done with the actual implementation
+            room.givenRoomMembersState(RoomMembersState.Ready(persistentListOf()))
+            // Wait for another update
+            skipItems(1)
+            // The members should be reloaded now
+            assertThat(awaitItem().roomMembers.dataOrNull()?.joined).isEmpty()
+        }
+    }
+
     @Test
     fun `open search`() = runTest {
         val presenter = createPresenter(