Name a sender the timeline has no profile for from the room member list

The timeline renders a message with the sender's raw Matrix ID whenever the
SDK has no profile for them, even though the room member list the same screen
already holds usually knows their display name and avatar.

The timeline item factory now falls back to the room member for a sender whose
profile is not resolved, both when the item is first built and when the member
list arrives afterwards, so the name and the avatar settle on the display name
instead of staying on the ID.

features/messages/impl/src/main/kotlin/io/element/android/features/messages/impl/timeline/factories/event/TimelineItemEventFactory.kt

@@ -28,10 +28,12 @@ import io.element.android.libraries.dateformatter.api.DateFormatterMode
 import io.element.android.libraries.designsystem.components.avatar.AvatarData
 import io.element.android.libraries.designsystem.components.avatar.AvatarSize
 import io.element.android.libraries.matrix.api.MatrixClient
+import io.element.android.libraries.matrix.api.core.UserId
 import io.element.android.libraries.matrix.api.permalink.PermalinkParser
 import io.element.android.libraries.matrix.api.room.RoomMember
 import io.element.android.libraries.matrix.api.timeline.MatrixTimelineItem
 import io.element.android.libraries.matrix.api.timeline.item.EventThreadInfo
+import io.element.android.libraries.matrix.api.timeline.item.event.ProfileDetails
 import io.element.android.libraries.matrix.api.timeline.item.event.getAvatarUrl
 import io.element.android.libraries.matrix.api.timeline.item.event.getDisambiguatedDisplayName
 import io.element.android.libraries.matrix.ui.messages.reply.map
@@ -64,7 +66,7 @@ class TimelineItemEventFactory(
         val currentSender = currentTimelineItem.event.sender
         val groupPosition =
             computeGroupPosition(currentTimelineItem, timelineItems, index)
-        val senderProfile = currentTimelineItem.event.senderProfile
+        val senderProfile = currentTimelineItem.event.senderProfile.orFallbackTo(roomMembers, currentSender)
         val sentTime = dateFormatter.format(
             timestamp = currentTimelineItem.event.timestamp,
             mode = DateFormatterMode.TimeOnly,
@@ -138,11 +140,32 @@ class TimelineItemEventFactory(
         roomMembers: List<RoomMember>,
         renderReadReceipts: Boolean,
     ): TimelineItem.Event {
+        val senderProfile = receivedMatrixTimelineItem.event.senderProfile.orFallbackTo(roomMembers, timelineItem.senderId)
         return timelineItem.copy(
+            senderProfile = senderProfile,
+            senderAvatar = timelineItem.senderAvatar.copy(
+                name = senderProfile.getDisambiguatedDisplayName(timelineItem.senderId),
+                url = senderProfile.getAvatarUrl(),
+            ),
             readReceiptState = receivedMatrixTimelineItem.computeReadReceiptState(roomMembers, renderReadReceipts)
         )
     }
 
+    /**
+     * The timeline only knows the profiles the SDK has resolved, so a sender it has nothing for is rendered as a raw
+     * user ID. The room member list usually knows that user, so use it rather than showing the ID.
+     */
+    private fun ProfileDetails.orFallbackTo(roomMembers: List<RoomMember>, senderId: UserId): ProfileDetails {
+        if (this is ProfileDetails.Ready) return this
+        val member = roomMembers.find { it.userId == senderId } ?: return this
+        return ProfileDetails.Ready(
+            displayName = member.displayName,
+            displayNameAmbiguous = member.isNameAmbiguous,
+            avatarUrl = member.avatarUrl,
+            displayedStatus = member.displayedStatus,
+        )
+    }
+
     private fun MatrixTimelineItem.Event.computeReactionsState(): TimelineItemReactions {
         if (!config.computeReactions) {
             return TimelineItemReactions(reactions = persistentListOf())

features/messages/impl/src/test/kotlin/io/element/android/features/messages/impl/timeline/factories/TimelineItemsFactoryTest.kt

@@ -16,7 +16,10 @@ import io.element.android.features.messages.impl.timeline.model.event.TimelineIt
 import io.element.android.libraries.matrix.api.core.UniqueId
 import io.element.android.libraries.matrix.api.timeline.MatrixTimelineItem
 import io.element.android.libraries.matrix.api.timeline.item.event.OtherMessageType
+import io.element.android.libraries.matrix.api.timeline.item.event.ProfileDetails
 import io.element.android.libraries.matrix.test.A_USER_ID
+import io.element.android.libraries.matrix.test.A_USER_ID_2
+import io.element.android.libraries.matrix.test.room.aRoomMember
 import io.element.android.libraries.matrix.test.timeline.aMessageContent
 import io.element.android.libraries.matrix.test.timeline.anEventTimelineItem
 import kotlinx.coroutines.test.TestScope
@@ -128,6 +131,74 @@ class TimelineItemsFactoryTest {
         }
     }
 
+    @Test
+    fun `a sender the timeline knows nothing about is named from the room member list`() = runTest {
+        val factory = aTimelineItemsFactory(
+            config = TimelineItemsFactoryConfig(
+                computeReadReceipts = false,
+                computeReactions = false,
+            )
+        )
+        val items = listOf(
+            MatrixTimelineItem.Event(
+                uniqueId = UniqueId("event-0"),
+                event = anEventTimelineItem(
+                    sender = A_USER_ID,
+                    senderProfile = ProfileDetails.Unavailable,
+                    content = aMessageContent(body = "A regular message"),
+                ),
+            ),
+        )
+        factory.timelineItems.test {
+            factory.replaceWith(
+                timelineItems = items,
+                roomMembers = listOf(aRoomMember(userId = A_USER_ID, displayName = "Alice")),
+                renderReadReceipts = false,
+            )
+            val event = awaitItem().filterIsInstance<TimelineItem.Event>().single()
+            assertThat(event.senderProfile).isEqualTo(
+                ProfileDetails.Ready(
+                    displayName = "Alice",
+                    displayNameAmbiguous = false,
+                    avatarUrl = null,
+                    displayedStatus = null,
+                )
+            )
+            assertThat(event.senderAvatar.name).isEqualTo("Alice")
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
+    @Test
+    fun `a sender the room member list knows nothing about keeps the profile the timeline gave`() = runTest {
+        val factory = aTimelineItemsFactory(
+            config = TimelineItemsFactoryConfig(
+                computeReadReceipts = false,
+                computeReactions = false,
+            )
+        )
+        val items = listOf(
+            MatrixTimelineItem.Event(
+                uniqueId = UniqueId("event-0"),
+                event = anEventTimelineItem(
+                    sender = A_USER_ID,
+                    senderProfile = ProfileDetails.Unavailable,
+                    content = aMessageContent(body = "A regular message"),
+                ),
+            ),
+        )
+        factory.timelineItems.test {
+            factory.replaceWith(
+                timelineItems = items,
+                roomMembers = listOf(aRoomMember(userId = A_USER_ID_2, displayName = "Bob")),
+                renderReadReceipts = false,
+            )
+            val event = awaitItem().filterIsInstance<TimelineItem.Event>().single()
+            assertThat(event.senderProfile).isEqualTo(ProfileDetails.Unavailable)
+            cancelAndIgnoreRemainingEvents()
+        }
+    }
+
     private suspend fun TestScope.groupPositionsOf(timestamps: List<Long>): List<TimelineItemGroupPosition> {
         val factory = aTimelineItemsFactory(
             config = TimelineItemsFactoryConfig(