Scaffold-DbContext does not generate correct model for FKs that reference unique constraint column in parent table

[cbrianball]

Due to a bug that was well-document in the issues (thank you!). I have recently upgraded to EFCore 2.0+.

The upgrade process was fairly painless, but when I went to regenerate my context with Scaffold-DbContext, I got the following warning:

Could not scaffold the foreign key 'dbo.Child(KeyId)'. A key for 'Key' was not found in the principal entity type 'Parent'.

The navigation property between the two entities was also lost.

Here's my simplified schema:

Parent{
Id //Primary Key
Key //Unique constraint
}

Child{
KeyId //Primary Key, Foreign Key -> Parent(Key)
}

The Child table is NOT pointing to the PK of the Parent table, but instead, another column that has a unique constraint. This worked fine under EF Core 1+, but the scaffolding tool doesn't seem to work correctly for EF Core 2+.

If I manually add the navigation properties to the entities and manually update the context to configure the model, everything works fine, so this appears to be a problem with the scaffolding tool (or some change in the conventions between EF Core 1 and EF Core 2 that the scaffolding tool uses).

Further technical details

EF Core version: 2.0.3
Database Provider: Microsoft.EntityFrameworkCore.SqlServer
Operating system: Windows 10
IDE: Visual Studio 2017 15.6.6

[smitpatel]

I tried to reproduce above using Entity Framework Core 2.2.0-preview2-35157 (latest package on NuGet) but the FK is scaffolded correctly for me.
Database schema

      CREATE TABLE [Parent] (
          [Id] int NOT NULL IDENTITY,
          [Key] int NOT NULL,
          CONSTRAINT [PK_Parent] PRIMARY KEY ([Id]),
          CONSTRAINT [AK_Parent_Key] UNIQUE ([Key])
      );
      CREATE TABLE [Child] (
          [KeyId] int NOT NULL,
          CONSTRAINT [PK_Child] PRIMARY KEY ([KeyId]),
          CONSTRAINT [FK_Child_Parent_KeyId] FOREIGN KEY ([KeyId]) REFERENCES [Parent] ([Key]) ON DELETE CASCADE
      );

Generated model

    public partial class Parent
    {
        public int Id { get; set; }
        public int Key { get; set; }

        public virtual Child Child { get; set; }
    }
    public partial class Child
    {
        public int KeyId { get; set; }

        public virtual Parent Key { get; set; }
    }

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

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

        public virtual DbSet<Child> Child { get; set; }
        public virtual DbSet<Parent> Parent { get; set; }

        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!optionsBuilder.IsConfigured)
            {
#warning To protect potentially sensitive information in your connection string, you should move it out of source code. See http://go.microsoft.com/fwlink/?LinkId=723263 for guidance on storing connection strings.
                optionsBuilder.UseSqlServer("Server=(localdb)\\mssqllocaldb;Database=_ModelApp;Trusted_Connection=True;Connect Timeout=5;ConnectRetryCount=0");
            }
        }

        protected override void OnModelCreating(ModelBuilder modelBuilder)
        {
            modelBuilder.Entity<Child>(entity =>
            {
                entity.HasKey(e => e.KeyId);

                entity.Property(e => e.KeyId).ValueGeneratedNever();

                entity.HasOne(d => d.Key)
                    .WithOne(p => p.Child)
                    .HasPrincipalKey<Parent>(p => p.Key)
                    .HasForeignKey<Child>(d => d.KeyId);
            });

            modelBuilder.Entity<Parent>(entity =>
            {
                entity.HasIndex(e => e.Key)
                    .HasName("AK_Parent_Key")
                    .IsUnique();
            });
        }
    }

Since original issue was reported for 2.0.3, it is likely to be fixed already.
If you are able to reproduce the issue in latest version then please provide SQL to generate database.

[smitpatel]

@ajcvickers to assign milestone.