Fix a bug with empty RecentlyAdded on the first DB created after bo…

…otstrapping.

src/NexusMods.MnemonicDB/Db.cs

@@ -39,7 +39,7 @@ public Db(ISnapshot snapshot, TxId txId, AttributeRegistry registry)
         _cache = new IndexSegmentCache();
         Snapshot = snapshot;
         BasisTxId = txId;
-        RecentlyAdded = new IndexSegment();
+        RecentlyAdded = snapshot.Datoms(SliceDescriptor.Create(txId, registry));
     }
 
     private Db(ISnapshot snapshot, TxId txId, AttributeRegistry registry, RegistryId registryId, IConnection connection, IndexSegmentCache newCache, IndexSegment recentlyAdded)

tests/NexusMods.MnemonicDB.Tests/DbTests.cs

@@ -2,6 +2,7 @@
 using DynamicData;
 using NexusMods.MnemonicDB.Abstractions;
 using NexusMods.Hashing.xxHash64;
+using NexusMods.MnemonicDB.Abstractions.BuiltInEntities;
 using NexusMods.MnemonicDB.Abstractions.DatomIterators;
 using NexusMods.MnemonicDB.Abstractions.Models;
 using NexusMods.MnemonicDB.Abstractions.Query;
@@ -601,7 +602,7 @@ public async Task CanObserveIndexChanges()
         var slice = SliceDescriptor.Create(Mod.Name, Connection.Db.Registry);
 
         // Setup the subscription
-        using var _ = ObservableDatoms.ObserveDatoms(Connection, slice)
+        using var _ = Connection.ObserveDatoms(slice)
             // Snapshot the values each time
             .QueryWhenChanged(datoms => datoms.Select(d => d.Resolved.ObjectValue.ToString()!).ToArray())
             // Add the changes to the list
@@ -625,6 +626,18 @@ public async Task CanObserveIndexChanges()
         await Verify(changes);
     }
 
+    [Fact]
+    public async Task CanGetInitialDbStateFromObservable()
+    {
+        var attrs = await Connection.ObserveDatoms(AttributeDefinition.UniqueId).FirstAsync();
+        attrs.TotalChanges.Should().BeGreaterThan(0);
+
+
+        attrs = await Connection.ObserveDatoms(AttributeDefinition.UniqueId).FirstAsync();
+        attrs.TotalChanges.Should().BeGreaterThan(0);
+
+    }
+
     /// <summary>
     /// Test for a flickering bug in UI users, where datoms that are changed result in a `add` and a `remove` operation
     /// causing the UI to flicker, instead we want to issue changes on a ScalarAttribute as a refresh/change