limit alias length in candidateAliasFromRoomName()

matrix-sdk-android/src/main/java/org/matrix/android/sdk/api/MatrixPatterns.kt

@@ -162,12 +162,14 @@ object MatrixPatterns {
         return order != null && order.length < 50 && order matches ORDER_STRING_REGEX
     }
 
-    fun candidateAliasFromRoomName(name: String): String {
-        return Regex("\\s").replace(name.lowercase(), "_").let {
-            "[^a-z0-9._%#@=+-]".toRegex().replace(it, "")
-        }.let { alias ->
-            if (alias.length > 255) alias.substring(0, 255) else alias
-        }
+    fun candidateAliasFromRoomName(roomName: String, domain: String): String {
+        return roomName.lowercase()
+                // Replace spaces by '_'
+                .let { Regex("\\s").replace(it, "_") }
+                // Remove all invalid chars
+                .let { "[^a-z0-9._%#@=+-]".toRegex().replace(it, "") }
+                // limit length
+                .substring(0, MatrixConstants.maxAliasLocalPartLength(domain))
     }
 
     /**

vector/src/main/java/im/vector/app/features/spaces/create/CreateSpaceViewModel.kt

@@ -134,7 +134,7 @@ class CreateSpaceViewModel @AssistedInject constructor(
                         )
                     } else {
                         val tentativeAlias =
-                                MatrixPatterns.candidateAliasFromRoomName(action.name)
+                                MatrixPatterns.candidateAliasFromRoomName(action.name, homeServerName)
                         copy(
                                 nameInlineError = null,
                                 name = action.name,