.NET 10 behavior change - Configuration binding an IEnumerable record has missing entries when nullable parameters are null

If you change Id and Name from record parameters to init-only properties then the .NET 9 behavior is restored and the list is deserialized with two entries:

public record User
{
    public int Id { get; init; }
    public string? Name { get; init; }
};

And, to test:

var options = builder.Configuration.GetSection("CustomOptions").Get();
Assert.That(options?.Users.Count() == 2); // PASSES

Notes -

• I have no explanation as to why this is true. The problem seems specific to types with parameterized constructors. If I modify your User type as follows, changing it from a record to a class with a single parameterized constructor:

  public class User
  {
      public User(int id, string? name) => (this.Id, this.Name) = (id, name); 
      public int Id { get; }
      public string? Name { get; }
  }
  

  Then .NET 9 loads both users (demo here) but .NET 10 can only load one of the two users (demo here).

  This appears to be a bug or regression. You might want to open an issue with Microsoft.

• The fact that the init-only record property Options.EnableFeatureX was deserialized successfully despite being null was the hint that led me to this workaround.

Demos:

• Working .NET 9 demo here.
• Failing .NET 10 demo using identical code here.
• Fixed .NET 10 demo using the modified User type here.