EntityTypeBuilder: .IsRequired() is ignored if used after .OnDelete()

[gukoff]

Problem

When configuring a non-nullable foreign key with FluentAPI, .isRequired() is ignored when called after .OnDelete().

Code

There are 2 models, connected by a 1-to-many relationship:

class Country {
   public long Id { get; set; }
}

class City {
   public long Id { get; set; }
   public Country Country { get; set; }
}

I'd like every city to belong to some country. This means, make the foreign key City.CountryId non-nullable.

Now, this doesn't work:

EntityTypeBuilder<City> builder;  // initialized

builder
.HasOne(city => city.Country)
.WithMany(country => country.Cities)
.OnDelete(DeleteBehavior.Restrict)
.IsRequired();   // after OnDelete

But this does:

EntityTypeBuilder<City> builder;  // initialized

builder
.HasOne(city => city.Country)
.WithMany(country => country.Cities)
.IsRequired()  // before OnDelete
.OnDelete(DeleteBehavior.Restrict);

The only difference is the order of IsRequired() and OnDelete().

The first (buggy) snippet generates a database migration with a nullable foreign key:

CountryId = table.Column<long>(type: "bigint", nullable: true)

And the second doesn't:

CountryId = table.Column<long>(type: "bigint", nullable: false)

Diagnostics

EF Core version: 5.0.0
Database provider: Microsoft.EntityFrameworkCore.SqlServer
Target framework: .NET 3.1
Operating system: MacOS (reproducible on Windows too)
IDE: command line

[migellars]

Hi, @gukoff but _I'd like every city to belong to some country. __ a country should have many cities

[ajcvickers]

@AndriySvyryd This repros for me and is a regression from 3.1.