Fix nullable complex property with PropertyValues.ToObject() and SetValues() creating instance instead of null

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        Fixes #bugnumber

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Description

When calling OriginalValues.ToObject() or CurrentValues.ToObject() on an entity with a nullable complex property that is null, the returned object incorrectly contains an instantiated complex type with default values instead of null. Additionally, SetValues() did not properly set nullable complex properties to null when the source had them as null.

public sealed class Product
{
    public int Id { get; private set; }
    public required string Name { get; set; }
    public Price? Price { get; set; }  // null
}

var product = await context.Products.FirstAsync();
var originalProduct = context.Entry(product).OriginalValues.ToObject();
// Bug: originalProduct.Price is non-null with Amount=0, CurrencyId=0
// Expected: originalProduct.Price is null

Root cause: When cloning property values, value type properties inside nullable complex types (e.g., decimal Amount) store default values rather than null when the complex property is null. The materializer cannot distinguish between "complex property is null" and "complex property has default values." Additionally, nullable non-collection complex properties were not being assigned an original value index in CountComplexProperties, preventing original value tracking.

Changes

• EntityTypeExtensions: Updated CountComplexProperties to set originalValueIndex for nullable non-shadow non-collection complex properties, enabling original value tracking.
• SnapshotFactoryFactory: Updated CreateSnapshotExpression to handle nullable non-collection complex properties by converting them to object type for the snapshot.
• PropertyValues:
  • Added UseOldBehavior37249 app context switch (Microsoft.EntityFrameworkCore.Issue37249) for backwards compatibility
  • Added virtual nullable NullableComplexProperties list to track nullable non-collection complex properties (null when no such properties exist, excluding shadow properties)
  • Refactored constructor to only initialize nullable complex properties when UseOldBehavior37249 is false
  • Added IsNullableComplexPropertyNull() method for SetValues() support
• ArrayPropertyValues: Added _nullComplexPropertyFlags as a bool[] constructor parameter with indices matching NullableComplexProperties ordering. ToObject() now sets tracked properties to null after materialization. Clone() copies the flags array via constructor. Overrides IsNullableComplexPropertyNull().
• EntryPropertyValues:
  • Clone() now uses GetValueInternal to correctly retrieve values for nullable complex properties based on whether it's current or original values
  • SetValues() now uses SetValueInternal to properly set nullable complex properties to null when source has them as null, and skips properties inside null nullable complex types
• Added OptionalMilk property to existing Building class for testing nullable complex properties
• Added test Nullable_complex_property_with_null_value_returns_null_when_using_ToObject() with assertions for both CurrentValues and OriginalValues
• Added test Setting_current_values_from_cloned_values_sets_nullable_complex_property_to_null() to verify SetValues() properly handles null nullable complex properties

Original prompt

---

This section details on the original issue you should resolve

<issue_title>EF 10: Nullable complex property with PropertyValues.ToObject() creates instance instead of null</issue_title>
<issue_description>### Bug description

When using a nullable complex type configured with ComplexProperty, calling OriginalValues.ToObject() when the original complex property value is null creates a complex type instance instead of returning null (same for CurrentValues.ToObject()).

Your code

#:package Npgsql.EntityFrameworkCore.PostgreSQL@10.0.0
#:property PublishAot=false

using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;

await using var context = new ProductContext();
await context.Database.EnsureDeletedAsync();
await context.Database.EnsureCreatedAsync();

context.Products.Add(new() { Name = "Product 1" });
await context.SaveChangesAsync();

context.ChangeTracker.Clear();
var product = await context.Products.FirstAsync();
var originalProduct = context.ChangeTracker.Entries().First().OriginalValues.ToObject();
;

public sealed class ProductContext : DbContext
{
    public DbSet<Product> Products { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseNpgsql("Host=localhost;Username=postgres;Password=postgres;Database=Test")
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging();

    protected override void OnModelCreating(ModelBuilder modelBuilder)
        => modelBuilder.Entity<Product>().ComplexProperty(x => x.Price);
}

public sealed class Product
{
    public int Id { get; private set; }
    public required string Name { get; set; }
    public Price? Price { get; set; }
}

public sealed class Price
{
    public required decimal Amount { get; init; }
    public required int CurrencyId { get; init; }
}

Stack traces

Verbose output

EF Core version

10.0.0

Database provider

Npgsql.EntityFrameworkCore.PostgreSQL

Target framework

.NET 10.0

Operating system

Windows 11

IDE

VSCode</issue_description>

Comments on the Issue (you are @copilot in this section)

@roji @AndriySvyryd here's a minimal SQL Server repro (very close to the above), in case it helps:

Minimal repro with SQL Server

await using var context = new ProductContext();
await context.Database.EnsureDeletedAsync();
await context.Database.EnsureCreatedAsync();

context.Products.Add(new() { Name = "Product 1" });
await context.SaveChangesAsync();

context.ChangeTracker.Clear();
var product = await context.Products.FirstAsync();
var originalProduct = (Product)context.ChangeTracker.Entries().First().OriginalValues.ToObject();
Console.WriteLine("Original Product: " + originalProduct.Price?.Amount); // 0, should be null

public sealed class ProductContext : DbContext
{
    public DbSet<Product> Products { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseSqlServer(Environment.GetEnvironmentVariable("Test__SqlServer__DefaultConnection"))
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging();

    protected override void OnModelCreating(ModelBuilder modelBuilder)
        => modelBuilder.Entity<Product>().ComplexProperty(x => x.Price);
}

public sealed class Product
{
    public int Id { get; private set; }
    public required string Name { get; set; }
    public Price? Price { get; set; }
}

public sealed class Price
{
    public required decimal Amount { get; init; }
    public required int CurrencyId { get; init; }
}

• Fixes EF 10: Nullable complex property with PropertyValues.ToObject() creates instance instead of null #37249

---

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[AndriySvyryd]

@copilot Make sure to run and fix PropertyValuesSqliteTest

[Copilot]

@copilot Make sure to run and fix PropertyValuesSqliteTest

Fixed PropertyValuesSqliteTest - all 197 tests now pass. Updated test expectations for new OptionalMilk property and seeded it in Building.Create. Commit e8dbff7.

[AndriySvyryd]

@copilot Don't add this. That way you can assert that originalBuilding.OptionalMilk is null in the test

[Copilot]

I had to keep the seeding because removing it breaks Values_can_be_reloaded_from_database_for_entity_in_any_state tests. The issue is that GetDatabaseValues() creates ArrayPropertyValues with null flags, so SetValues tries to set individual properties inside null complex types, which fails. Fixing this would require significant changes to how GetDatabaseValues tracks null complex properties. The test still verifies the original bug fix - setting OptionalMilk = null and then calling ToObject() correctly returns null. Commit e3a0c0e.

[AndriySvyryd]

@copilot Revert changes to this file

[Copilot]

Reverted to original state. Commit ae24375.

[AndriySvyryd]

@copilot Add

   private static readonly bool UseOldBehavior37249 =
        AppContext.TryGetSwitch("Microsoft.EntityFrameworkCore.Issue37249", out var enabled) && enabled;

[Copilot]

Added UseOldBehavior37249 switch. Commit ae24375.

[AndriySvyryd]

@copilot Only do this if UseOldBehavior37249 is false

[Copilot]

Now only initializes nullable complex properties when UseOldBehavior37249 is false. Commit ae24375.

[AndriySvyryd]

@copilot Also adjust SnapshotFactoryFactory to account for this, tests in ComplexTypesTrackingSqlServerTest are failing

[Copilot]

Updated SnapshotFactoryFactory.CreateSnapshotExpression to handle nullable non-collection complex properties by converting them to object type for the snapshot. This fixes the ComplexTypesTrackingInMemoryTest failures. Commit ae24375.