Can't delete entity with complex collection

[roji]

Trying to delete an entity which has a complex (JSON) collection seems to fail.

The complex entry at ordinal '0' for the collection 'RootEntity.Users' cannot be accessed as the containing entry is in the deleted state.

Minimal repro

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

var entity = new RootEntity { Users = [new User { Name = "User" }] };
context.RootEntities.Add(entity);
await context.SaveChangesAsync();

context.ChangeTracker.Clear();

RootEntity loadedEntity = await context.RootEntities.SingleAsync();
context.RootEntities.Remove(loadedEntity);
await context.SaveChangesAsync();

public class BlogContext : DbContext
{
    public DbSet<RootEntity> RootEntities { 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<RootEntity>().ComplexCollection(x => x.Users, x => x.ToJson());
    }
}

public class RootEntity
{
    public int Id { get; set; }
    public List<User> Users { get; set; } = [];
}

public class User
{
    public string Name { get; set; }
}

Full exception

Unhandled exception. System.InvalidOperationException: The complex entry at ordinal '0' for the collection 'RootEntity.Users' cannot be accessed as the containing entry is in the deleted state.
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntryBase.InternalComplexCollectionEntry.GetEntry(Int32 ordinal, Boolean original)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.InternalEntryBase.GetComplexCollectionEntry(IComplexProperty property, Int32 ordinal)
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.WriteJson(Utf8JsonWriter writer, Object value, IInternalEntry parentEntry, IPropertyBase property, Nullable`1 ordinal, Boolean isCollection, Boolean isTopLevel)
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.WriteJson(Utf8JsonWriter writer, Object value, IInternalEntry parentEntry, IPropertyBase property, Nullable`1 ordinal, Boolean isCollection, Boolean isTopLevel)
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.<GenerateColumnModifications>g__HandleJson|40_8(List`1 columnModifications, <>c__DisplayClass40_0&)
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.GenerateColumnModifications()
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.<>c.<get_ColumnModifications>b__33_0(ModificationCommand command)
   at Microsoft.EntityFrameworkCore.Internal.NonCapturingLazyInitializer.EnsureInitialized[TParam,TValue](TValue& target, TParam param, Func`2 valueFactory)
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.get_ColumnModifications()
   at Microsoft.EntityFrameworkCore.Update.UpdateSqlGenerator.AppendDeleteReturningOperation(StringBuilder commandStringBuilder, IReadOnlyModificationCommand command, Int32 commandPosition, Boolean& requiresTransaction)
   at Microsoft.EntityFrameworkCore.SqlServer.Update.Internal.SqlServerUpdateSqlGenerator.AppendDeleteOperation(StringBuilder commandStringBuilder, IReadOnlyModificationCommand command, Int32 commandPosition, Boolean& requiresTransaction)
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.AddCommand(IReadOnlyModificationCommand modificationCommand)
   at Microsoft.EntityFrameworkCore.SqlServer.Update.Internal.SqlServerModificationCommandBatch.AddCommand(IReadOnlyModificationCommand modificationCommand)
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.TryAddCommand(IReadOnlyModificationCommand modificationCommand)
   at Microsoft.EntityFrameworkCore.SqlServer.Update.Internal.SqlServerModificationCommandBatch.TryAddCommand(IReadOnlyModificationCommand modificationCommand)
   at Microsoft.EntityFrameworkCore.Update.Internal.CommandBatchPreparer.CreateCommandBatches(IEnumerable`1 commandSet, Boolean moreCommandSets, Boolean assertColumnModification, ParameterNameGenerator parameterNameGenerator)+MoveNext()
   at Microsoft.EntityFrameworkCore.Update.Internal.CommandBatchPreparer.BatchCommands(IList`1 entries, IUpdateAdapter updateAdapter)+MoveNext()
   at Microsoft.EntityFrameworkCore.Update.Internal.BatchExecutor.ExecuteAsync(IEnumerable`1 commandBatches, IRelationalConnection connection, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.Storage.RelationalDatabase.SaveChangesAsync(IList`1 entries, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(IList`1 entriesToSave, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChangesAsync(StateManager stateManager, Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.SqlServer.Storage.Internal.SqlServerExecutionStrategy.ExecuteAsync[TState,TResult](TState state, Func`4 operation, Func`4 verifySucceeded, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChangesAsync(Boolean acceptAllChangesOnSuccess, CancellationToken cancellationToken)
   at Program.<Main>$(String[] args) in /Users/roji/projects/test/Program.cs:line 22
   at Program.<Main>$(String[] args) in /Users/roji/projects/test/Program.cs:line 22
   at Program.<Main>(String[] args)

[peterwurzinger]

Seems like today is the day of complex collections, +1 on this exact issue.

Just to share a minor finding I had here as well (coming from #37361):
This only fails if the complex collection is not empty.
So replacing
var entity = new RootEntity { Users = [new User { Name = "User" }] };
with
var entity = new RootEntity { Users = [] };
does not trigger the exception on save.

@roji Is there a known workaround besides going back to OwnsMany ?

[roji]

@peterwurzinger give us a bit of time to investigate this, we'll see if there's a workaround. In any case, depending on what the fix looks like, IMHO this seems important enough for a 10.0.3 servicing.