Merge pull request #2460 from vitorpamplona/claude/fix-empty-groups-display-MO6E9

Show placeholder notes for empty Marmot groups in chat list

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/AccountFeedContentStates.kt

@@ -56,6 +56,8 @@ import com.vitorpamplona.amethyst.ui.screen.loggedIn.shorts.dal.ShortsFeedFilter
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.video.dal.VideoFeedFilter
 import com.vitorpamplona.amethyst.ui.screen.loggedIn.webBookmarks.dal.WebBookmarkFeedFilter
 import kotlinx.coroutines.CoroutineScope
+import kotlinx.coroutines.Dispatchers
+import kotlinx.coroutines.launch
 
 class AccountFeedContentStates(
     val account: Account,
@@ -100,6 +102,19 @@ class AccountFeedContentStates(
 
     val webBookmarks = FeedContentState(WebBookmarkFeedFilter(account), scope, LocalCache)
 
+    init {
+        // Marmot group list changes (new group, group marked known, group
+        // metadata synced) don't flow through LocalCache.newEventBundles, so
+        // the additive update path can't see them. Force a full feed rebuild
+        // whenever the list changes so empty groups appear and placeholder
+        // rows get replaced by real messages.
+        scope.launch(Dispatchers.IO) {
+            account.marmotGroupList.groupListChanges.collect {
+                dmKnown.invalidateData()
+            }
+        }
+    }
+
     suspend fun init() {
         notificationSummary.initializeSuspend()
     }

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/rooms/ChatroomHeaderCompose.kt

@@ -85,7 +85,11 @@ fun ChatroomHeaderCompose(
     accountViewModel: AccountViewModel,
     nav: INav,
 ) {
-    if (baseNote.event != null) {
+    val isEmptyMarmotPlaceholder =
+        baseNote.event == null &&
+            baseNote.inGatherers?.any { it is MarmotGroupChatroom } == true
+
+    if (baseNote.event != null || isEmptyMarmotPlaceholder) {
         ChatroomComposeChannelOrUser(baseNote, accountViewModel, nav)
     } else {
         val hasEvent by observeNoteHasEvent(baseNote, accountViewModel)
@@ -248,21 +252,27 @@ private fun MarmotGroupRoomCompose(
     accountViewModel: AccountViewModel,
     nav: INav,
 ) {
-    val authorName by observeUserName(lastMessage.author!!, accountViewModel)
     val displayName by chatroom.displayName.collectAsStateWithLifecycle()
     val unread by chatroom.unreadCount.collectAsStateWithLifecycle()
 
+    val author = lastMessage.author
     val noteEvent = lastMessage.event
-    val description = noteEvent?.content?.take(200)
-
     val groupName = displayName?.takeIf { it.isNotBlank() } ?: "Group ${chatroom.nostrGroupId.take(8)}"
 
+    val lastContent =
+        if (author != null && noteEvent != null) {
+            val authorName by observeUserName(author, accountViewModel)
+            "$authorName: ${noteEvent.content.take(200)}"
+        } else {
+            stringRes(R.string.marmot_group_no_messages_yet)
+        }
+
     ChannelName(
         channelIdHex = chatroom.nostrGroupId,
         channelPicture = null,
         channelTitle = { modifier -> ChannelTitleWithLabelInfo(groupName, R.string.marmot_group, modifier) },
         channelLastTime = lastMessage.createdAt(),
-        channelLastContent = "$authorName: $description",
+        channelLastContent = lastContent,
         hasNewMessages = unread > 0,
         loadProfilePicture = accountViewModel.settings.showProfilePictures(),
         loadRobohash = accountViewModel.settings.isNotPerformanceMode(),

amethyst/src/main/java/com/vitorpamplona/amethyst/ui/screen/loggedIn/chats/rooms/dal/ChatroomListKnownFeedFilter.kt

@@ -79,7 +79,7 @@ class ChatroomListKnownFeedFilter(
 
         val marmotGroups =
             account.marmotGroupList.rooms.mapNotNull { _, chatroom ->
-                chatroom.newestMessage
+                chatroom.newestMessage ?: chatroom.placeholderNote()
             }
 
         return (privateMessages + publicChannels + ephemeralChats + marmotGroups).sortedWith(DefaultFeedOrder)

amethyst/src/main/res/values/strings.xml

@@ -284,6 +284,7 @@
 
     <string name="public_chat">Public Chat</string>
     <string name="marmot_group">MLS Group</string>
+    <string name="marmot_group_no_messages_yet">No messages yet</string>
     <string name="public_chat_title">Public Chat Metadata</string>
     <string name="public_chat_explainer">Public chats are visible to everyone on Nostr and anyone
         can participate on them. They are great for open communities around specific topics.

commons/src/commonMain/kotlin/com/vitorpamplona/amethyst/commons/model/marmotGroups/MarmotGroupChatroom.kt

@@ -69,6 +69,27 @@ class MarmotGroupChatroom(
      */
     var ownerSentMessage: Boolean = false
 
+    // Synthetic note used by list views to represent the group when no
+    // messages have been received yet. Lazily created and kept stable so
+    // equality-based feed diffing treats it as the same row across refreshes.
+    private var cachedPlaceholder: Note? = null
+
+    @Synchronized
+    fun placeholderNote(): Note {
+        val existing = cachedPlaceholder
+        if (existing != null) return existing
+        val created =
+            Note(placeholderIdHex(nostrGroupId)).apply {
+                addGatherer(this@MarmotGroupChatroom)
+            }
+        cachedPlaceholder = created
+        return created
+    }
+
+    companion object {
+        fun placeholderIdHex(nostrGroupId: HexKey): HexKey = "marmot-empty-$nostrGroupId"
+    }
+
     private var changesFlow: WeakReference<MutableSharedFlow<ListChange<Note>>> = WeakReference(null)
 
     fun changesFlow(): MutableSharedFlow<ListChange<Note>> {