Add helper method for safer realm Find<T>

osu.Game/Database/ModelManager.cs

@@ -3,6 +3,7 @@
 
 using System;
 using System.Collections.Generic;
+using System.Diagnostics;
 using System.IO;
 using System.Linq;
 using osu.Framework.Platform;
@@ -47,13 +48,16 @@ private void performFileOperation(TModel item, Action<TModel> operation)
             // This method should be removed as soon as all the surrounding pieces support non-detached operations.
             if (!item.IsManaged)
             {
-                // We use RealmLive here as it handled re-retrieval and refreshing of realm if required.
-                new RealmLive<TModel>(item.ID, Realm).PerformWrite(i =>
+                // Importantly, begin the realm write *before* re-fetching, else the update realm may not be in a consistent state
+                // (ie. if an async import finished very recently).
+                Realm.Realm.Write(realm =>
                 {
-                    operation(i);
+                    var managed = realm.FindWithRefresh<TModel>(item.ID);
+                    Debug.Assert(managed != null);
+                    operation(managed);
 
                     item.Files.Clear();
-                    item.Files.AddRange(i.Files.Detach());
+                    item.Files.AddRange(managed.Files.Detach());
                 });
             }
             else

osu.Game/Database/RealmExtensions.cs

@@ -8,6 +8,31 @@ namespace osu.Game.Database
 {
     public static class RealmExtensions
     {
+        /// <summary>
+        /// Performs a <see cref="Realm.Find{T}(System.Nullable{long})"/>.
+        /// If a match was not found, a <see cref="Realm.Refresh"/> is performed before trying a second time.
+        /// This ensures that an instance is found even if the realm requested against was not in a consistent state.
+        /// </summary>
+        /// <param name="realm"></param>
+        /// <param name="id"></param>
+        /// <typeparam name="T"></typeparam>
+        /// <returns></returns>
+        public static T? FindWithRefresh<T>(this Realm realm, Guid id) where T : IRealmObject
+        {
+            var found = realm.Find<T>(id);
+
+            if (found == null)
+            {
+                // It may be that we access this from the update thread before a refresh has taken place.
+                // To ensure that behaviour matches what we'd expect (the object *is* available), force
+                // a refresh to bring in any off-thread changes immediately.
+                realm.Refresh();
+                found = realm.Find<T>(id);
+            }
+
+            return found;
+        }
+
         /// <summary>
         /// Perform a write operation against the provided realm instance.
         /// </summary>

osu.Game/Database/RealmLive.cs

@@ -41,24 +41,6 @@ public RealmLive(T data, RealmAccess realm)
             dataIsFromUpdateThread = ThreadSafety.IsUpdateThread;
         }
 
-        /// <summary>
-        /// Construct a new instance of live realm data from an ID.
-        /// </summary>
-        /// <param name="id">The ID of an already-persisting realm instance.</param>
-        /// <param name="realm">The realm factory the data was sourced from. May be null for an unmanaged object.</param>
-        public RealmLive(Guid id, RealmAccess realm)
-            : base(id)
-        {
-            data = retrieveFromID(realm.Realm);
-
-            if (data.IsNull())
-                throw new ArgumentException("Realm instance for provided ID could not be found.", nameof(id));
-
-            this.realm = realm;
-
-            dataIsFromUpdateThread = ThreadSafety.IsUpdateThread;
-        }
-
         /// <summary>
         /// Perform a read operation on this live object.
         /// </summary>
@@ -80,7 +62,7 @@ public override void PerformRead(Action<T> perform)
                     return;
                 }
 
-                perform(retrieveFromID(r));
+                perform(r.FindWithRefresh<T>(ID)!);
                 RealmLiveStatistics.USAGE_ASYNC.Value++;
             });
         }
@@ -102,7 +84,7 @@ public override TReturn PerformRead<TReturn>(Func<T, TReturn> perform)
 
             return realm.Run(r =>
             {
-                var returnData = perform(retrieveFromID(r));
+                var returnData = perform(r.FindWithRefresh<T>(ID)!);
                 RealmLiveStatistics.USAGE_ASYNC.Value++;
 
                 if (returnData is RealmObjectBase realmObject && realmObject.IsManaged)
@@ -159,24 +141,9 @@ private void ensureDataIsFromUpdateThread()
             }
 
             dataIsFromUpdateThread = true;
-            data = retrieveFromID(realm.Realm);
-            RealmLiveStatistics.USAGE_UPDATE_REFETCH.Value++;
-        }
-
-        private T retrieveFromID(Realm realm)
-        {
-            var found = realm.Find<T>(ID);
+            data = realm.Realm.FindWithRefresh<T>(ID)!;
 
-            if (found == null)
-            {
-                // It may be that we access this from the update thread before a refresh has taken place.
-                // To ensure that behaviour matches what we'd expect (the object *is* available), force
-                // a refresh to bring in any off-thread changes immediately.
-                realm.Refresh();
-                found = realm.Find<T>(ID)!;
-            }
-
-            return found;
+            RealmLiveStatistics.USAGE_UPDATE_REFETCH.Value++;
         }
     }