Finish the implementation of the SaveChanges support for JSON-mapped complex collections

src/EFCore/ChangeTracking/ComplexEntry`.cs → src/EFCore/ChangeTracking/ComplexElementEntry`.cs

@@ -81,7 +81,7 @@ public ComplexElementEntry(InternalComplexEntry internalEntry)
     /// </param>
     /// <returns>An object that exposes change tracking information and operations for the given property.</returns>
     public virtual PropertyEntry<TEntity, TProperty> Property<TProperty>(
-        Expression<Func<TComplexProperty, TProperty>> propertyExpression)
+        Expression<Func<TComplexProperty, TProperty?>> propertyExpression)
     {
         Check.NotNull(propertyExpression, nameof(propertyExpression));
 

src/EFCore/ChangeTracking/ComplexPropertyEntry`.cs

@@ -95,7 +95,7 @@ public virtual PropertyEntry<TEntity, TProperty> Property<TProperty>(
     /// </param>
     /// <returns>An object that exposes change tracking information and operations for the given property.</returns>
     public virtual ComplexPropertyEntry<TEntity, TNestedComplexProperty> ComplexProperty<TNestedComplexProperty>(
-        Expression<Func<TComplexProperty, TNestedComplexProperty>> propertyExpression)
+        Expression<Func<TComplexProperty, TNestedComplexProperty?>> propertyExpression)
     {
         Check.NotNull(propertyExpression);
 

src/EFCore/ChangeTracking/EntityEntry`.cs

@@ -74,7 +74,7 @@ public virtual PropertyEntry<TEntity, TProperty> Property<TProperty>(
     /// </param>
     /// <returns>An object that exposes change tracking information and operations for the given property.</returns>
     public virtual ComplexPropertyEntry<TEntity, TProperty> ComplexProperty<TProperty>(
-        Expression<Func<TEntity, TProperty>> propertyExpression)
+        Expression<Func<TEntity, TProperty?>> propertyExpression)
     {
         Check.NotNull(propertyExpression);
 

src/EFCore/ChangeTracking/Internal/ChangeDetector.cs

@@ -321,11 +321,11 @@ public bool DetectComplexCollectionChanges(InternalEntryBase entry, IComplexProp
 
         Check.DebugAssert(!complexProperty.ComplexType.ClrType.IsValueType, $"Expected {complexProperty.Name} to be a collection of reference types.");
 
-        var changesFound = false;
         var originalEntries = new Dictionary<object, InternalComplexEntry>(ReferenceEqualityComparer.Instance);
         var currentCollection = (IList?)entry[complexProperty];
         // The elements in the original collection might be the same instances as in the current collection, so their properties shouldn't be used for comparison.
         var originalCollection = (IList?)entry.GetOriginalValue(complexProperty);
+        var changesFound = (currentCollection == null) != (originalCollection == null);
 
         entry.EnsureComplexCollectionEntriesCapacity(complexProperty, currentCollection?.Count ?? 0, originalCollection?.Count ?? 0, trim: false);
         var originalNulls = new HashSet<int>();

src/EFCore/ChangeTracking/Internal/InternalComplexEntry.cs

@@ -255,8 +255,9 @@ protected override void OnStateChanged(EntityState oldState)
     /// </summary>
     public override void AcceptChanges()
     {
-        if (EntityState == EntityState.Added
-            || ContainingEntry.GetComplexCollectionEntry(ComplexProperty, Ordinal) == this)
+        if (Ordinal != -1
+            && (EntityState == EntityState.Added
+                || ContainingEntry.GetComplexCollectionOriginalEntry(ComplexProperty, Ordinal) == this))
         {
             OriginalOrdinal = Ordinal;
         }

src/EFCore/ChangeTracking/Internal/InternalEntryBase.InternalComplexCollectionEntry.cs

@@ -149,24 +149,31 @@ public void AcceptChanges()
 
             if (_originalEntries != null)
             {
-                foreach (var entry in _originalEntries)
+                for (var i = 0; i < _originalEntries.Count; i++)
                 {
+                    var entry = _originalEntries[i];
                     if (entry == null
                         || entry.EntityState != EntityState.Deleted)
                     {
                         continue;
                     }
                     entry.AcceptChanges();
+                    // The entry was deleted, so AcceptChanges removed it from the list
+                    i--;
                 }
             }
 
             if (_entries != null)
             {
-                _originalEntries = new List<InternalComplexEntry?>(_entries.Count);
-                foreach (var entry in _entries)
+                _originalEntries ??= new List<InternalComplexEntry?>(_entries.Count);
+                _originalEntries.Clear();
+                for (var i = 0; i < _entries.Count; i++)
+                {
+                    _originalEntries.Add(_entries[i]);
+                }
+                for (var i = 0; i < _originalEntries.Count; i++)
                 {
-                    _originalEntries.Add(entry);
-                    entry?.AcceptChanges();
+                    _originalEntries[i]?.AcceptChanges();
                 }
             }
             else
@@ -195,10 +202,14 @@ public void RejectChanges()
 
             if (_originalEntries != null)
             {
-                _entries = new List<InternalComplexEntry?>(_originalEntries.Count);
-                foreach (var entry in _originalEntries)
+                _entries ??= new List<InternalComplexEntry?>(_originalEntries.Count);
+                _entries.Clear();
+                for (var i = 0; i < _originalEntries.Count; i++)
+                {
+                    _entries.Add(_originalEntries[i]);
+                }
+                foreach (var entry in _entries)
                 {
-                    _entries.Add(entry);
                     entry?.Ordinal = entry.OriginalOrdinal;
                 }
             }