Discrepancy in nullability for parameters OptionalValues.OpenApi vs OptionalValues.Swashbuckle

[espenrl]

First of all thanks for a great library. Worthy of being part of STJ itself.

Using OptionalValues.Swashbuckle I found nullability to not being output for parameters (in swagger.json) . I then tried OptionalValues.OpenApi which do behave as expected.

Example code that reproduces the issue

public record UserUpdateRecord(Guid UserId)
{
    public OptionalValue<string?> Name { get; set; }
    public OptionalValue<string?> Email { get; set; }
}

[HttpPut]
public async Task<ActionResult<UserResponse>> UpdateUser(UserUpdateRecord userUpdateRecord)
{
    ...
}

Code difference OptionalValues.OpenApi vs OptionalValues.Swashbuckle

There is a difference in the source code with regards to handling of parameters and nullability. Perhaps that is the source of the issue, see code below.

OptionalValues.OpenApi

OptionalValues/src/OptionalValues.OpenApi/OptionalValuesSchemaTransformer.cs

Lines 121 to 131 in 41e4686

	private static NullabilityInfo? GetNullabilityInfo(ICustomAttributeProvider memberInfo)
	{
	var nullabilityInfoContext = new NullabilityInfoContext();
	return memberInfo switch
	{
	PropertyInfo propertyInfo => nullabilityInfoContext.Create(propertyInfo),
	FieldInfo fieldInfo => nullabilityInfoContext.Create(fieldInfo),
	ParameterInfo parameterInfo => nullabilityInfoContext.Create(parameterInfo),
	_ => null,
	};
	}

OptionalValues.Swashbuckle

OptionalValues/src/OptionalValues.Swashbuckle/OptionalValueDataContractResolver.cs

Lines 93 to 102 in 41e4686

	private static NullabilityInfo? GetNullabilityInfo(MemberInfo memberInfo)
	{
	var nullabilityInfoContext = new NullabilityInfoContext();
	return memberInfo switch
	{
	PropertyInfo propertyInfo => nullabilityInfoContext.Create(propertyInfo),
	FieldInfo fieldInfo => nullabilityInfoContext.Create(fieldInfo),
	_ => null,
	};

[desjoerd]

Will look into it! I also see that there is also some test coverage missing here around nullable.

To help me check, which version of Swashbuckle do you use and which version of OpenAPI (3.0 or 3.1)?

[espenrl]

My bad, versions matter a lot in these matters. Thanks for looking into it.

• .NET / ASP.NET 10.0.7
• OptionalValues 0.9.1
• Swashbuckle.AspNetCore.SwaggerGen 10.1.7 (the output states OpenAPI 3.0.4)

[desjoerd]

I updated the logic to match with OptionalValues.OpenApi, it did not resolve the issue. When debugging it marked the properties as nullable correctly but in the final openapi output it still saw them as not nullable.

After some digging I think it's because of Swashbuckle marking the property as not nullable when the member info is not nullable (which is true, because OptionalValue<> is a struct, so it's not nullable). The related logic is here https://github.com/domaindrivendev/Swashbuckle.AspNetCore/blob/62b8cbcc959fb3e2570711f7ce175af2f8dff9bf/src/Swashbuckle.AspNetCore.SwaggerGen/SchemaGenerator/SchemaGenerator.cs#L138-L148

I also created an issue at Swashbuckle. domaindrivendev/Swashbuckle.AspNetCore#3977.

At the moment it will not overwrite it to become not null when SupportNonNullableReferenceTypes is set to false instead of true:

    new SchemaGeneratorOptions
    {
        SupportNonNullableReferenceTypes = false,
    }

[espenrl]

That's unfortunate, though a great finding. I'll subscribe to the issue at Swashbuckle and see what happens. At least OptionalValues.OpenApi works so I may just migrate away from Swashbuckle.