Implement calcDisplayname without local part

lib/src/room.dart

@@ -1134,8 +1134,13 @@ class Room {
   final Set<String> _requestingMatrixIds = {};
 
   /// Requests a missing [User] for this room. Important for clients using
-  /// lazy loading.
-  Future<User> requestUser(String mxID, {bool ignoreErrors = false}) async {
+  /// lazy loading. If the user can't be found this method tries to fetch
+  /// the displayname and avatar from the profile if [requestProfile] is true.
+  Future<User> requestUser(
+    String mxID, {
+    bool ignoreErrors = false,
+    bool requestProfile = true,
+  }) async {
     if (getState(EventTypes.RoomMember, mxID) != null) {
       return getState(EventTypes.RoomMember, mxID).asUser;
     }
@@ -1147,10 +1152,24 @@ class Room {
         EventTypes.RoomMember,
         mxID,
       );
+    } catch (exception) {
+      if (!ignoreErrors) {
+        _requestingMatrixIds.remove(mxID);
+        rethrow;
+      }
+    }
+    if (resp == null && requestProfile) {
+      try {
+        final profile = await client.api.requestProfile(mxID);
+        resp = {
+          'displayname': profile.displayname,
+          'avatar_url': profile.avatarUrl,
+        };
       } catch (exception) {
         _requestingMatrixIds.remove(mxID);
         if (!ignoreErrors) rethrow;
       }
+    }
     if (resp == null) {
       return null;
     }

lib/src/user.dart

@@ -97,11 +97,14 @@ class User extends Event {
   /// has no displayname. If [formatLocalpart] is true, then the localpart will
   /// be formatted in the way, that all "_" characters are becomming white spaces and
   /// the first character of each word becomes uppercase.
-  String calcDisplayname({bool formatLocalpart = true}) {
+  /// If [mxidLocalPartFallback] is true, then the local part of the mxid will be shown
+  /// if there is no other displayname available. If not then this will return "Unknown user".
+  String calcDisplayname(
+      {bool formatLocalpart = true, bool mxidLocalPartFallback = true}) {
     if (displayName?.isNotEmpty ?? false) {
       return displayName;
     }
-    if (stateKey != null) {
+    if (stateKey != null && mxidLocalPartFallback) {
       if (!formatLocalpart) {
         return stateKey.localpart;
       }
@@ -113,7 +116,7 @@ class User extends Event {
       }
       return words.join(' ');
     }
-    return 'Unknown User';
+    return 'Unknown user';
   }
 
   /// Call the Matrix API to kick this user from this room.

test/user_test.dart

@@ -81,6 +81,8 @@ void main() {
       expect(user2.calcDisplayname(), 'SuperAlice');
       expect(user3.calcDisplayname(), 'Alice Mep');
       expect(user3.calcDisplayname(formatLocalpart: false), 'alice_mep');
+      expect(
+          user3.calcDisplayname(mxidLocalPartFallback: false), 'Unknown user');
     });
     test('kick', () async {
       await client.checkServer('https://fakeserver.notexisting');