ModelState validation changes when adding a new property to an existing model

[bkoelman]

Is there an existing issue for this?

• I have searched the existing issues

Describe the bug

Adding a new property to an existing model changes the required-ness of another existing (unmodified) property when nullable reference types are enabled. As a result, the outcome of ModelState validation changes.

Expected Behavior

Adding a new property should not change the validation of another existing (unmodified) property.

Steps To Reproduce

• In Visual Studio 2022, create a new API project: File > New > Project > ASP.NET Core Web API (accept defaults).
• Add the following code to a new file in the project:

  public abstract class Identifiable<TId>
  {
      public virtual TId Id { get; set; } = default!;
  
      //public string? Version { get; set; }
  }
  
  public class Customer : Identifiable<string?>
  {
      public string Name { get; set; } = null!;
  
      [Range(1, 150)]
      public int Age { get; set; }
  }

• Add the next method to Controllers\WeatherForecastController.cs:

  [HttpPost]
  public virtual IActionResult Post([FromBody] Customer customer)
  {
      if (!ModelState.IsValid)
      {
          return BadRequest(ModelState);
      }
  
      return Ok($"Hello '{customer.Name}' with ID '{customer.Id}'.");
  }

• Run the application.
• From the Swagger UI in the browser, expand "POST WeatherForecast" and click Try it out. Replace the request body with {} and click Execute.
• Note the response contains two errors:

    "errors": {
      "Age": [
        "The field Age must be between 1 and 150."
      ],
      "Name": [
        "The Name field is required."
      ]
    }

• Stop the application and uncomment the Version property from the first code snippet.
• Run the application and execute the same POST request from Swagger UI in the browser.
• Note the response now contains three errors:

    "errors": {
      "Id": [
        "The Id field is required."
      ],
      "Age": [
        "The field Age must be between 1 and 150."
      ],
      "Name": [
        "The Name field is required."
      ]
    }

Exceptions (if any)

No response

.NET Version

6.0.203

Anything else?

I traced this down to DataAnnotationsMetadataProvider. Uncommenting the Version property makes the C# compiler switch from [NullableAttribute] to [NullableContextAttribute], causing the metadata provider to bail out early due to the use of generics here (or gets it wrong here, I don't remember exactly).

This appears to be fixed in #39219. So I've tested with .NET 7 Preview4 and can confirm the problem no longer occurs there.

Feel free to close this issue, as the problem is already solved. I just thought it would be good to log this for awareness and traceability.

I don't think it makes sense to backport this to .NET 6, because NullabilityInfoContext doesn't behave correctly in the .NET 6 runtime version:

var property = typeof(Customer).GetProperty("Id")!;

var nullContext = new NullabilityInfoContext();
var nullability = nullContext.Create(property);
var isOptional = nullability.ReadState != NullabilityState.NotNull;

// .NET 6 v6.0.300:
// class Customer : Identifiable<string> => isOptional: true
// class Customer : Identifiable<string?> => isOptional: true

// .NET 7 Preview 4:
// class Customer : Identifiable<string> => isOptional: false
// class Customer : Identifiable<string?> => isOptional: true

[brunolins16]

@bkoelman Thanks for reporting the issue. As you mentioned this behavior was changed in .NET 7 when we moved to NullabilityInfoContext instead of the attributes lookup and we should have this issue fixed.

Feel free to reopen or create a new issue if you see any other related problems.