[NancyFx] response of type 'file' not supported

Description

If a swagger specification defines a response of type file,
then the generated nancy server stub produces code that compiles but that fails at runtime (see below).

Swagger-codegen version

Current master (2.3.1+)

Swagger declaration file content or url

If you post the code inline, please wrap it with

swagger: "2.0"
info:
  version: "1.0.0"
  title: Demo

paths:
  /foo:
    get:
      summary: retrieve a file
      responses:
        200:
          description: success
          schema:
            type: file

Command line used for generation

generate -i C:\temp\file_response\swagger.yaml -o C:/temp/file_response/nancy/ -l nancyfx --additional-properties packageContext=v1,interfacePrefix=I

Related issues/PRs

Not that I'm aware of.

Suggest a fix/enhancement

The swagger spec from above generates the following Nancy Module:

public sealed class DefaultModule : NancyModule
    {
        /// <summary>
        /// Sets up HTTP methods mappings.
        /// </summary>
        /// <param name="service">Service handling requests</param>
        public DefaultModule(IDefaultService service) : base("")
        { 
            Get["/foo"] = parameters =>
            {
                
                return service.FooGet(Context);
            };
        }
    }

This code does not compile as service.FooGet will return a System.IO.Stream that is not accepted by nancy. I suggest to change the signature of the FooGet method from

System.IO.Stream FooGet(NancyContext context)

to

Nancy.Response FooGet(NancyContext context)

. In this way, the implementor of the service can return the file using e.g. a Nancy.StreamResponse or a Nancy.GenericFileResponse.

Reproduce the issue with the supplied Swagger YAML and NancyFX generation command, then inspect the generated DefaultModule and FooGet service signature shown in the report. Verify the generated response handling against Nancy's expected response types; done means a file response can be implemented and returned without the generated server failing at runtime.