Response headers not being displayed in UI

I wrote a custom SwaggerResponseHeader attribute to document response headers. I also wrote a custom AddResponseHeadersFilter to add the documentation to the swagger output. I then used the attribute on one of the controller actions. All works fine. The swagger output contains the specified response header and the editor at editor.swagger.io nicely displays the response header.

My API’s swagger UI however does not display the response header. Is there a way to fix that?

Attribute

public class SwaggerResponseHeaderAttribute : Attribute
{
    public SwaggerResponseHeaderAttribute(HttpStatusCode statusCode, string name, string type, string description)
    {
        StatusCode = statusCode;
        Name = name;
        Type = type;
        Description = description;
    }

    public HttpStatusCode StatusCode { get; set; }
    public string Name { get; set; }
    public string Type { get; set; }
    public string Description { get; set; }

}

Filter

public class AddResponseHeadersFilter : IOperationFilter
{
    public void Apply(Operation operation, SchemaRegistry schemaRegistry, ApiDescription apiDescription)
    {
        var responseAttributes = apiDescription.GetControllerAndActionAttributes<SwaggerResponseHeaderAttribute>();

        foreach (var attr in responseAttributes)
        {
            var response = operation.responses.FirstOrDefault(x => x.Key == ((int)attr.StatusCode).ToString(CultureInfo.InvariantCulture)).Value;

            if (response != null)
            {
                if (response.headers == null)
                {
                    response.headers = new Dictionary<string, Header>();
                }

                response.headers.Add(attr.Name, new Header {description = attr.Description, type = attr.Type});
            }
        }
    }
}

Controller

[SwaggerResponseRemoveDefaults]
[SwaggerResponse(HttpStatusCode.Created, "Created", typeof(Person))]
[SwaggerResponseHeader(HttpStatusCode.Created, "Location", "string", "Location of the newly created resource")]
public IHttpActionResult Post(Person person)
{
    //...
}        

Documentation (part)

{
    "responses":{
        "201":{
            "description":"Created",
            "schema":{
                "$ref":"#/definitions/Person"
            },
            "headers":{
                "Location":{
                    "description":"Location of the newly created resource.",
                    "type":"string"
                }
            }
        }
    }
}

[mattfrear]

@WhitWaldo yep, I ported it to OpenApi almost a year ago.

https://github.com/mattfrear/Swashbuckle.AspNetCore.Filters/blob/master/src/Swashbuckle.AspNetCore.Filters/ResponseHeaders/AddResponseHeadersFilter.cs

Or you can get it from my NuGet (Swashbuckle.AspNetCore.Filters).

[WhitWaldo]

Small tweak to @rocklan 's response to accommodate 5.0.0-rc5 (and the shift to OpenApi):

public class AddResponseHeadersFilter : IOperationFilter { public void Apply(Operation operation, OperationFilterContext context) { var responseAttributes = context.MethodInfo.GetCustomAttributes<ProducesResponseTypeHeader>();

    foreach (var attr in responseAttributes)
    {
        var response = operation.Responses.FirstOrDefault(
            x => x.Key == ((int)attr.StatusCode).ToString(CultureInfo.InvariantCulture)).Value;

        if (response != null)
        {
            if (response.Headers == null)
                response.Headers = new Dictionary<string, OpenApiHeader>();

            response.Headers.Add(attr.Name, new Header { 
                Description = attr.Description,
                Content = new Dictionary<string, OpenApiMediaType> { 
                      [attr.Type] = new OpenApiMediaType()
                }
            });
        }
    }
   
}

}