Null HttpContext with long polling

[JamesNK]

A hub method that accesses the HttpContext can get null instead if the method was invoked while the poll request ended.

SignalR/src/Microsoft.AspNetCore.Sockets.Http/HttpConnectionDispatcher.cs

Line 279 in 0e38ee3

connection.SetHttpContext(null);

This has shown up with HubConnectionTests.ClientCanSendHeaders(transportType: LongPolling) on OSX build.

https://travis-ci.org/aspnet/SignalR/jobs/355210173#L1309

[xUnit.net 00:00:06.1150930]     Microsoft.AspNetCore.SignalR.Client.FunctionalTests.HubConnectionTests.ClientCanSendHeaders(transportType: LongPolling) [FAIL]
Failed   Microsoft.AspNetCore.SignalR.Client.FunctionalTests.HubConnectionTests.ClientCanSendHeaders(transportType: LongPolling)
Error Message:
 Microsoft.AspNetCore.SignalR.Client.HubException : An unexpected error occurred invoking 'GetHeaderValues' on the server. InvalidOperationException: Unable to get HttpContext from request.
Stack Trace:
   at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()

[analogrelay]

Yeah, this is a tricky one because the connection is long-living but the HttpContext is only associated with a single Send, Poll, EventSource stream or WebSocket request. Perhaps we need to just remove the HttpContext entirely and copy any relevant data into the ConnectionContext.

[davidfowl]

Since we are decoupled from the actual hub invocation process we're going to remove the HttpContext from the connection features. Instead, we're going to need to copy data from the HttpContext (Headers and QueryString).

[analogrelay]

Also Connection info (IP Addresses, ports)

[davidfowl]

@anurse I had an evil idea. Still set an HttpContext but with the copied data. The benefit is that it just works with all of the APIs that take an http context (like the auth methods) but it's harmless since it isn't valid as write to or read from (the bodies), and it has the properties that people want.

[analogrelay]

It's not that crazy. We'd need to poison, or null-out things like the Body stream. It would take a lot of effort to get it right though, possibly more than just copying the things we know we want.

[davidfowl]

Yep, I'm going to do this.