Drop the sender's name from the room list preview of two-person rooms

The room list preview prefixes the sender's name unless the room is a
direct message. A room that was created as a group and later converted to
a direct message is not marked as one by the server, so its preview kept
naming the only other person in it on every message, while iOS did not.

The prefix now depends on how many people are actually in the room rather
than on the direct message flag, which is the behaviour asked for in the
issue: no name while only two people can be talking, the name back as
soon as a third joins.

Part of #1548

features/home/impl/src/main/kotlin/io/element/android/features/home/impl/datasource/RoomListRoomSummaryFactory.kt

@@ -19,6 +19,7 @@ import io.element.android.libraries.designsystem.components.avatar.AvatarSize
 import io.element.android.libraries.eventformatter.api.RoomLatestEventFormatter
 import io.element.android.libraries.matrix.api.room.CallIntentConsensus
 import io.element.android.libraries.matrix.api.room.CurrentUserMembership
+import io.element.android.libraries.matrix.api.room.RoomInfo
 import io.element.android.libraries.matrix.api.roomlist.LatestEventValue
 import io.element.android.libraries.matrix.api.roomlist.RoomSummary
 import io.element.android.libraries.matrix.ui.model.dmUserStatus
@@ -47,7 +48,7 @@ class RoomListRoomSummaryFactory(
                 mode = DateFormatterMode.TimeOrDate,
                 useRelative = true,
             ),
-            latestEvent = computeLatestEvent(roomSummary.latestEvent, roomInfo.isDm),
+            latestEvent = computeLatestEvent(roomSummary.latestEvent, roomInfo.hasOnlyTwoMembers()),
             avatarData = avatarData,
             userDefinedNotificationMode = roomInfo.userDefinedNotificationMode,
             hasRoomCall = roomInfo.hasRoomCall,
@@ -81,6 +82,10 @@ class RoomListRoomSummaryFactory(
         )
     }
 
+    private fun RoomInfo.hasOnlyTwoMembers(): Boolean {
+        return isDm || activeMembersCount <= 2
+    }
+
     private fun computeLatestEvent(latestEvent: LatestEventValue, dm: Boolean): LatestEvent {
         return when (latestEvent) {
             is LatestEventValue.None -> {

features/home/impl/src/test/kotlin/io/element/android/features/home/impl/datasource/RoomListRoomSummaryFactoryTest.kt

@@ -8,10 +8,36 @@
 
 package io.element.android.features.home.impl.datasource
 
+import com.google.common.truth.Truth.assertThat
 import io.element.android.libraries.dateformatter.api.DateFormatter
 import io.element.android.libraries.dateformatter.test.FakeDateFormatter
 import io.element.android.libraries.eventformatter.api.RoomLatestEventFormatter
 import io.element.android.libraries.eventformatter.test.FakeRoomLatestEventFormatter
+import io.element.android.libraries.matrix.test.room.aRoomInfo
+import io.element.android.libraries.matrix.test.room.aRoomSummary
+import org.junit.Test
+
+class RoomListRoomSummaryFactoryTest {
+    @Test
+    fun `a room with two members does not prefix its preview with the sender`() {
+        val formatter = FakeRoomLatestEventFormatter()
+        val factory = aRoomListRoomSummaryFactory(roomLatestEventFormatter = formatter)
+
+        factory.create(aRoomSummary(info = aRoomInfo(isDm = false, activeMembersCount = 2)))
+
+        assertThat(formatter.lastIsDmRoom).isTrue()
+    }
+
+    @Test
+    fun `a room with more than two members prefixes its preview with the sender`() {
+        val formatter = FakeRoomLatestEventFormatter()
+        val factory = aRoomListRoomSummaryFactory(roomLatestEventFormatter = formatter)
+
+        factory.create(aRoomSummary(info = aRoomInfo(isDm = false, activeMembersCount = 3)))
+
+        assertThat(formatter.lastIsDmRoom).isFalse()
+    }
+}
 
 fun aRoomListRoomSummaryFactory(
     dateFormatter: DateFormatter = FakeDateFormatter { _, _, _ -> "Today" },

libraries/eventformatter/test/src/main/kotlin/io/element/android/libraries/eventformatter/test/FakeRoomLatestEventFormatter.kt

@@ -14,11 +14,16 @@ import io.element.android.libraries.matrix.api.roomlist.LatestEventValue
 class FakeRoomLatestEventFormatter : RoomLatestEventFormatter {
     private var result: CharSequence? = null
 
+    var lastIsDmRoom: Boolean? = null
+        private set
+
     override fun format(latestEvent: LatestEventValue.Local, isDmRoom: Boolean): CharSequence? {
+        lastIsDmRoom = isDmRoom
         return result
     }
 
     override fun format(latestEvent: LatestEventValue.Remote, isDmRoom: Boolean): CharSequence? {
+        lastIsDmRoom = isDmRoom
         return result
     }