Add IHttpContextFactory.DisposeHttpContext(...) and call it from the end of the request

[Eilon]

Discussed with @lodejard and @davidfowl :

Change IHttpContextFactory to have two methods:

    public interface IHttpContextFactory
    {
        HttpContext Create(IFeatureCollection featureCollection); // just renamed
        void Dispose(HttpContext httpContext); // add this
    }

Need to call the new Dispose method from the end of the request from within the server, which is where the context was created.

[Tratcher]

This affects the layering of multiple APIs and packages:

• IHttpContextFactory should move from the Hosting package to Hosting.Server.Abstractions if we're maintaining the ability to author servers without a direct dependency on Hosting.
• This and Revisit IServerFactory.Start #395 negate any separation between Http.Abstractions and Http.Features, both are now required in all server and middleware scenarios so we might as well merge them.

[davidfowl]

Yah that's what I said :)

[davidfowl]

@Tratcher as part of this we should probably move IHttpContextFactory into HttpAbstractions (maybe with HttpContext in abstractions.)

[Tratcher]

I think Hosting.Server.Abstractions is more appropriate, it's a service only used in association with servers.

[benaadams]

Devil's advocate IDisposable HttpContext that calls IHttpContextFactory.Dispose(this)?

Pro

using (var httpContext =  httpContextFactory.Create(featureCollection))
{
  ...
}

rather than

var httpContext = httpContextFactory.Create(featureCollection);
try 
{
 ...
} 
finally 
{
   httpContextFactory.Dispose(httpContext);
}

Con
Puts a dependency and reference in to HttpContext so may not be good

HttpContext(IHttpContextFactory factory, IFeatureCollection featureCollection)
{
   _factory = factory;
   _featureCollection = featureCollection;
}

Dispose()
{
   _factory.Dispose(this);
}

Also may mean people might think they can do multi-dispose which would be bad if the factory was doing pooling.

[Tratcher]

@benaadams Yeah, I don't recommend it as there's only one place in the stack where it's good/safe to dispose. You don't want other people thinking they can dispose it.

[benaadams]

@Tratcher good enough reason for me 👍 As you say might end up with people trying to dispose it all over the place; just thought I'd bring it up