Stack overflow when using circular composite key dependencies

[Stratster]

After upgrading to .net6 release version 6.0.0 from 6.0.0-rc2 we encountered a fatal stack overflow while running our application.
We searched for a while and found that our cyclic entity dependencies with composite keys are now broken.

I attached a very simple test project for reproducing the error.
It is a very simple file structure: 2 entities and the DbContext

public partial class Parent
{
    public long ID { get; set; }

    public long? FavoriteChildID { get; set; }

    public virtual Child FavoriteChild { get; set; }

    public virtual List<Child> Children { get; set; }
}

public partial class Child
{
    public long ParentID { get; set; } // Key order 1

    public long ID { get; set; } // Key order 2

    public virtual Parent Parent { get; set; }
}

public partial class Context : DbContext
{
    public Context()
    {
    }

    public Context(DbContextOptions<Context> options)
        : base(options)
    {
    }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        if (!optionsBuilder.IsConfigured)
            optionsBuilder.UseInMemoryDatabase("test");
    }

    public virtual DbSet<Parent> Parents { get; set; }
    public virtual DbSet<Child> Children { get; set; }
    
    protected override void OnModelCreating(ModelBuilder modelBuilder)
    {
        modelBuilder.Entity<Parent>(entity =>
        {
            entity.HasKey(d => d.ID);

            entity.HasOne(d => d.FavoriteChild)
                .WithOne()
                .HasForeignKey<Parent>(d => new { d.ID, d.FavoriteChildID });
        });

        modelBuilder.Entity<Child>(entity =>
        {
            entity.HasKey(d => new { d.ParentID, d.ID });

            entity.HasOne(d => d.Parent)
                .WithMany(p => p.Children)
                .HasForeignKey(d => d.ParentID);
        });

        OnModelCreatingPartial(modelBuilder);
    }

    partial void OnModelCreatingPartial(ModelBuilder modelBuilder);
}

The main method of the project is as simple as

using BreakEFCore6;

var ctx = new Context();

var q = from p in ctx.Parents
        where p.FavoriteChildID.HasValue
        select p;

var parents = q.ToList();

This error occured with the provided InMemory-database as well as our SqlServer in production. (Seems provider independent)

While researching the error we assume this fix could have something to do with it:
Commit: 539aee7e60694dd608d82a4884908b8f1127a39e
We added some printf-debugging in

Microsoft.EntityFrameworkCore.Metadata.Internal.Property.cs

public virtual ValueComparer? GetValueComparer()
{
    Console.WriteLine(this.ToString()); // THIS LINE HERE
    return (ValueComparer?)this[CoreAnnotationNames.ValueComparer]
           ?? FindFirstDifferentPrincipal()?.GetValueComparer()
           ?? TypeMapping?.Comparer;
}

which results in:

Property: Child.ParentID (long) Required PK FK AfterSave:Throw
Property: Parent.ID (long) Required PK FK Index AfterSave:Throw
Property: Child.ParentID (long) Required PK FK AfterSave:Throw
Property: Parent.ID (long) Required PK FK Index AfterSave:Throw
Property: Child.ParentID (long) Required PK FK AfterSave:Throw
Property: Parent.ID (long) Required PK FK Index AfterSave:Throw
Property: Child.ParentID (long) Required PK FK AfterSave:Throw
Property: Parent.ID (long) Required PK FK Index AfterSave:Throw
Property: Child.ParentID (long) Required PK FK AfterSave:Throw
Property: Parent.ID (long) Required PK FK Index AfterSave:Throw
...

And the stack overflow output is:

Stack overflow.
   at System.Collections.Generic.List`1[[System.__Canon, System.Private.CoreLib, Version=6.0.0.0, Culture=neutral, PublicKeyToken=7cec85d7bea7798e]].System.Collections.Generic.IEnumerable<T>.GetEnumerator()
   at Microsoft.EntityFrameworkCore.Metadata.IReadOnlyProperty.FindFirstPrincipal()
   at Microsoft.EntityFrameworkCore.Metadata.IProperty.FindFirstPrincipal()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.FindFirstDifferentPrincipal()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.Microsoft.EntityFrameworkCore.Metadata.IProperty.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.Microsoft.EntityFrameworkCore.Metadata.IProperty.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.Microsoft.EntityFrameworkCore.Metadata.IProperty.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.Microsoft.EntityFrameworkCore.Metadata.IProperty.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.Microsoft.EntityFrameworkCore.Metadata.IProperty.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.Microsoft.EntityFrameworkCore.Metadata.IProperty.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.Microsoft.EntityFrameworkCore.Metadata.IProperty.GetValueComparer()
   at Microsoft.EntityFrameworkCore.Metadata.Internal.Property.GetValueComparer()
...

Minimal test project

BreakEFCore6.zip

[ajcvickers]

FYI for those impacted by this issue: EF Core 6.0.1 is now available from NuGet.