Nullable property is required if there is another not-nullable string property in model

[SonicGD]

Hello. After i upgraded to preview7 from preview5 some of my queries started to throw exceptions cause of null values in database for nullable properties. I reproduced this in test project and there is something strange. I have Nullable reference types enabled.

Steps to reproduce

Define model class

public class Bar
{
    [Key] public Guid Id { get; set; }
    public Guid? EmptyId { get; set; }
}

Now generate migration:

migrationBuilder.CreateTable(
    name: "Bars",
    columns: table => new
    {
        Id = table.Column<Guid>(nullable: false),
        EmptyId = table.Column<Guid>(nullable: true)
    },
    constraints: table =>
    {
        table.PrimaryKey("PK_Bars", x => x.Id);
    });

Property EmptyId has nullable: true as it should.

Now let's create another model with additional sting property

public class Foo
{
    [Key] public Guid Id { get; set; }
    public Guid? EmptyId { get; set; }
    public string SomeString { get; set; }
}

and generate new migration

migrationBuilder.CreateTable(
    name: "Foos",
    columns: table => new
    {
        Id = table.Column<Guid>(nullable: false),
        EmptyId = table.Column<Guid>(nullable: false),
        SomeString = table.Column<string>(nullable: false)
    },
    constraints: table =>
    {
        table.PrimaryKey("PK_Foos", x => x.Id);
    });

Here property EmptyId has nullable: false for some reasons.

If we change SomeString to nullable string

public class FooBar
{
    [Key] public Guid Id { get; set; }
    public Guid? EmptyId { get; set; }
    public string? SomeString { get; set; }
}

then both properties are correctly nullable:

migrationBuilder.CreateTable(
    name: "FooBars",
    columns: table => new
    {
        Id = table.Column<Guid>(nullable: false),
        EmptyId = table.Column<Guid>(nullable: true),
        SomeString = table.Column<string>(nullable: true)
    },
    constraints: table =>
    {
        table.PrimaryKey("PK_FooBars", x => x.Id);
    });

and if we move EmptyId to base class:

public abstract class BaseBaz
{
    public Guid? EmptyId { get; set; }
}

public class Baz : BaseBaz
{
    [Key] public Guid Id { get; set; }
    public string SomeString { get; set; } = default!;
}

it will be nullable:

migrationBuilder.CreateTable(
    name: "Bazes",
    columns: table => new
    {
        Id = table.Column<Guid>(nullable: false),
        EmptyId = table.Column<Guid>(nullable: true),
        SomeString = table.Column<string>(nullable: false)
    },
    constraints: table =>
    {
        table.PrimaryKey("PK_Bazes", x => x.Id);
    });

Further technical details

EF Core version: 3.0.0-preview7.19362.6
Database Provider: Microsoft.EntityFrameworkCore.SqlServer and Npgsql.EntityFrameworkCore.PostgreSQL
Operating system: Windows 10 18941
IDE: dotnet cli

[ajcvickers]

@roji Looks like our first bug with nullable reference types!

[roji]

@SonicGD thanks for reporting! Your sample indeed exposed some bugs in the nullability handling, have submitted a PR with the fixes. Hopefully you can continue testing with the preview8 nightlies once that's merged!