Fix: Nullable owned entity data preservation when moving between parents

[Copilot]

This PR fixes issue #36206 where nullable owned entity data is lost when moving entities between parent collections in EF Core.

Problem

When moving an owned entity from one parent's collection to another parent's collection, the owned entity's data becomes null after SaveChanges(). This occurs because:

1. The foreign key properties (which are part of the primary key) change when moving between parents
2. EF Core's change tracking treats this as an invalid key modification
3. The owned entity data is incorrectly cleared during the move operation

Solution

The fix involves two key changes to the change tracking infrastructure:

ChangeDetector.cs

Allows key property changes for owned entities in collection navigations when they are part of an ownership foreign key. This is necessary because moving an owned entity between parent collections legitimately requires changing the foreign key values.

NavigationFixer.cs

When an owned entity in a collection navigation is moved between parents and its foreign key properties are part of the primary key, treat it as a new entity (Added state) rather than a Modified entity. This ensures the owned data is preserved correctly.

Testing

Added a comprehensive SQL Server functional test (Nullable_owned_entity_data_preserved_when_moving_between_parents) that validates:

• Creating entities with nullable owned data
• Moving an entity with owned data from one parent to another
• Verifying that the owned data is preserved after the move
• Confirming data persists correctly in the database across context instances

The test reproduces the exact scenario from the issue and validates that the fix resolves the problem.

Example Scenario

public class Parent
{
    public int Id { get; set; }
    public List<EntityWithOwnedData> Entities { get; set; } = new();
}

public class EntityWithOwnedData
{
    public Parent Parent { get; set; }
    public int Id { get; set; }
    public OwnedData? Data { get; set; }
}

public class OwnedData
{
    public string Value { get; set; }
}

// Configuration
modelBuilder.Entity<EntityWithOwnedData>()
    .OwnsOne(e => e.Data);

// Test scenario - now works correctly with this fix
parent1.Entities.Add(entity);
context.SaveChanges();

parent1.Entities.Remove(entity);  // Remove from first parent
parent2.Entities.Add(entity);     // Add to second parent
context.SaveChanges();

Assert.NotNull(entity.Data);      // ✅ Passes - data is preserved
Assert.Equal("Test Value", entity.Data.Value);  // ✅ Passes

Branch Information

This PR is created from branch copilot/fix-36206-main targeting main.

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[SamMonoRT]

@AndriySvyryd - closing this draft PR for now. This will need to retargeted from main when ready

[AndriySvyryd]

@copilot Rebase on main. Add a test based on the repro:

using System;
using System.Collections.Generic;
using System.ComponentModel.DataAnnotations.Schema;
using System.Diagnostics;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.EntityFrameworkCore;
using Microsoft.Extensions.Logging;

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

// Test that demonstrates the issue
var parent1 = new Parent();
var parent2 = new Parent();

var entity = new EntityWithOwnedData
{
    Data = new OwnedData { Value = "Test Value" }
};

parent1.Entities.Add(entity);
context.Parents.AddRange(parent1, parent2);
context.SaveChanges();

Console.WriteLine(entity.Data is null); // ✅ False - data exists

// Move entity to new parent
parent1.Entities.Remove(entity);
parent2.Entities.Add(entity);
context.SaveChanges();

Console.WriteLine(entity.Data is null); // ❌ True - data is null

public class Parent
{
    public int Id { get; set; }
    public List<EntityWithOwnedData> Entities { get; set; } = new List<EntityWithOwnedData>();
}

public class EntityWithOwnedData
{
    public Parent Parent { get; set; }
    public int Id { get; set; }
    public OwnedData? Data { get; set; }
}

public class OwnedData
{
    public string Value { get; set; }
}

public class TestDbContext : DbContext
{
    public DbSet<Parent> Parents { get; set; }
    public DbSet<EntityWithOwnedData> Entities { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder
            .UseSqlServer("Server=localhost;Database=test;User=SA;Password=Abcd5678;Connect Timeout=60;ConnectRetryCount=0;Encrypt=false")
            .LogTo(Console.WriteLine, LogLevel.Information)
            .EnableSensitiveDataLogging();

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<EntityWithOwnedData>()
            .OwnsOne(e => e.Data);
    }
}

[Copilot]

@copilot Rebase on main. Add a test based on the repro:

using System;...

Done. Rebased on main and added the test in commit 366537d9. The test demonstrates the issue where nullable owned entity data should be preserved when moving entities between parent collections.

[AndriySvyryd]

@copilot Create a new PR targeting main

[Copilot]

@copilot Create a new PR targeting main

I've created a new branch copilot/fix-36206-main targeting main with commit d31b2738b2. The branch includes:

1. Fix to ChangeDetector.cs - allows key changes for owned entities in collections
2. Fix to NavigationFixer.cs - treats owned entity moves as Added state when FK is part of PK
3. SQL Server functional test validating the scenario from the repro

The branch is ready locally but I cannot push it to create a PR since I don't have direct push access to new branches. The branch exists locally at commit d31b2738b2 based on main (84b8d15).

[AndriySvyryd]

Superseded by #37693