Default swagger content-type for Response

Since latest 2-3 releases (I don’t know exactly which one) I notice that the default content-type selected on the swagger HTML dropdown menu for the method reponse, is not "application/json" but "text/plain".

If I don’t change it everytime before clicking on Try button, I get an error because no content-type negotiation for responses is allowed in my application. I think that "application/json" should be the right default value, but anyway is it possible to set the default content-type for response in Swagger configuration to avoid changing it everytime?

This is my actual configuration

public void ConfigureServices(IServiceCollection services)
{
	services.AddMvc(config =>
	{
		// HTTP 406 when not supported format is requested by client
		config.ReturnHttpNotAcceptable = true;
	})
	.SetCompatibilityVersion(CompatibilityVersion.Version_2_1)
	// Add FluentValidation
	.AddFluentValidation(fv => fv.RegisterValidatorsFromAssemblyContaining<MachineCreateModelValidator>());

	// Add API versioning
	services.AddApiVersioning(options =>
	{
		options.AssumeDefaultVersionWhenUnspecified = true;
		options.DefaultApiVersion = new ApiVersion(1, 0);
		options.ReportApiVersions = true;
	});
}

The HTML result

[OculiViridi]

I temporary solved the problem by simply putting the Produces attribute on the top of all of my controllers, like this:

[Produces("application/json")]
[ApiVersion("1.0")]
[SwaggerTag("Machines", Description = "Core operations on machines.")]
public class MachinesController : ControllerBase
{ }

UPDATE 2019/07/23

I forgot to mention that if you are using a common base class for all your Controllers, you can just put the Produces attribute only on the base class.

[ApiController]
[Produces("application/json")]
[Route("api/v{version:apiVersion}/[controller]/[action]")]
public abstract class BaseController : ControllerBase
{
    // TODO: Add needed common methods/properties for all Controllers
}

[Authorize]
[ApiVersion("1.0")]
[OpenApiTag("Machines", Description = "Operations on machines")]
public class MachinesController : BaseController
{
    // TODO: Add controller methods
}

[Authorize]
[ApiVersion("1.0")]
[OpenApiTag("Machines", Description = "Operations on machines")]
public class DriversController : BaseController
{
    // TODO: Add controller methods
}

@RSuter But I don’t know if it is really necessary, since you said that should come automatically. Any news?

[OculiViridi]

Also There are one more temporary resolving way.

Just override Produces on AddSwaggerDocument when add swagger document on startup.cs

services.AddSwaggerDocument(settings =>
{
	settings.PostProcess = document => document.Produces = new List<string>
	{
		"application/json",
		"text/json"
	};
});

@js-lee0624

Just a note for users reading the suggestion, from NSwag v13, there was a refactoring, so the method is called AddOpenApiDocument instead of AddSwaggerDocument.