ArgumentNullException when inserting record contains nested objects

Start by running the supplied .NET 9 reproduction with Npgsql.EntityFrameworkCore.PostgreSQL 9.0.4 and nested owned JSON objects. Trace the failure through the stack locations ModificationCommand.GenerateColumnModifications and NpgsqlUpdateSqlGenerator.AppendInsertOperation. Done means inserting the reproduced record no longer throws and the relevant regression is covered by a test.

Dears,

At first, thank you for this great library which is making our lives easy :)

I'm running into an issue when trying to insert a new record that contains nested objects into my table.

The error is below followed by a complete code to reproduce the error.

Unhandled exception. System.ArgumentNullException: Value cannot be null. (Parameter 'key')
   at System.Collections.Generic.Dictionary`2.FindValue(TKey key)
   at System.Collections.Generic.Dictionary`2.TryGetValue(TKey key, TValue& value)
   at Microsoft.EntityFrameworkCore.Update.ModificationCommand.<GenerateColumnModifications>g__HandleJson|41_4(List`1 columnModifications, <>c__DisplayClass41_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 Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlUpdateSqlGenerator.AppendInsertOperation(StringBuilder commandStringBuilder, IReadOnlyModificationCommand command, Int32 commandPosition, Boolean overridingSystemValue, Boolean& requiresTransaction)
   at Npgsql.EntityFrameworkCore.PostgreSQL.Update.Internal.NpgsqlUpdateSqlGenerator.AppendInsertOperation(StringBuilder commandStringBuilder, IReadOnlyModificationCommand command, Int32 commandPosition, Boolean& requiresTransaction)
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.AddCommand(IReadOnlyModificationCommand modificationCommand)
   at Microsoft.EntityFrameworkCore.Update.ReaderModificationCommandBatch.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.Execute(IEnumerable`1 commandBatches, IRelationalConnection connection)
   at Microsoft.EntityFrameworkCore.Storage.RelationalDatabase.SaveChanges(IList`1 entries)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(IList`1 entriesToSave)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(StateManager stateManager, Boolean acceptAllChangesOnSuccess)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.<>c.<SaveChanges>b__112_0(DbContext _, ValueTuple`2 t)
   at Npgsql.EntityFrameworkCore.PostgreSQL.Storage.Internal.NpgsqlExecutionStrategy.Execute[TState,TResult](TState state, Func`3 operation, Func`3 verifySucceeded)
   at Microsoft.EntityFrameworkCore.ChangeTracking.Internal.StateManager.SaveChanges(Boolean acceptAllChangesOnSuccess)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChanges(Boolean acceptAllChangesOnSuccess)
   at Microsoft.EntityFrameworkCore.DbContext.SaveChanges()

Code:

// I'm using Npgsql.EntityFrameworkCore.PostgreSQL

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using Microsoft.EntityFrameworkCore;


using var context = new BloggingContext();

context.Blogs.Add(new Blog
{
    JustJson = new JustJson
    {
        Name = "SomeJson",
        ChildJustJson = new ChildJustJson()
    },
    Url = "SomeUrl"
});

context.SaveChanges();

public class BloggingContext : DbContext
{
    public DbSet<Blog> Blogs { get; set; }
    public DbSet<Post> Posts { get; set; }

    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Blog>()
            .OwnsOne(c => c.JustJson, d =>
            {
                d.ToJson();
                d.OwnsOne(x => x.ChildJustJson, builder => builder.ToJson());
            });
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        => optionsBuilder.UseNpgsql("Host=localhost:5432;Username=postgres;Password=06DKqM9jyLcEtd8n;Database=test");
}

public class Blog
{
    [DatabaseGenerated(DatabaseGeneratedOption.Identity)]
    [Key]
    public int BlogId { get; set; }
    public string? Url { get; set; }
    public JustJson? JustJson { get; set; }
    public List<Post> Posts { get; set; } = new List<Post>();
}

public class Post
{
    public int PostId { get; set; }
    public string? Title { get; set; }
    public string? Content { get; set; }

    public int BlogId { get; set; }
    public Blog Blog { get; set; }
}

public class JustJson
{
    public string? Name { get; set; }
    public ChildJustJson? ChildJustJson { get; set; }
}

public class ChildJustJson
{
    public string? Name { get; set; }
}

I tried everything I can think of, from enabling and tracing logging, searching on the internet but can't find an answer to the issue. The work around is to store the the property as serialized text but would love to keep that as a last resort.

  options.EnableDetailedErrors();
  options.EnableSensitiveDataLogging();
  options.LogTo(Console.WriteLine, (_, level) => level == LogLevel.Trace);

I hope if anyone can help me in solving this issue.

Thanks,
Asif

Versions:
.Net: v9
Npgsql.EntityFrameworkCore.PostgreSQL: v9.0.4
Microsoft.EntityFrameworkCore.Design: 9.0.4