[WIP] Fix SignalR HTTP/2 WebSocket connection when SkipNegotiation is true

[Copilot]

Thanks for asking me to work on this. I will get started on it and keep this PR's description up to date as I form a plan and make progress.

Original description:

Problem

SignalR client throws an exception when trying to connect to HTTP/2 servers with SkipNegotiation = true:

An HttpMessageInvoker instance must be passed to ConnectAsync when using HTTP/2. (Parameter 'options')

Root Cause

In WebSocketsTransport.DefaultWebSocketFactory, the allowHttp2 variable is set to false when authentication methods like Negotiate Auth are used. However, this logic doesn't account for scenarios where SkipNegotiation = true, which bypasses the authentication negotiation entirely.

When allowHttp2 = false, the code path that passes the HttpClient as an invoker to ConnectAsync is skipped, causing the HTTP/2 connection to fail.

Solution

Modify the logic in DefaultWebSocketFactory to allow HTTP/2 when SkipNegotiation = true, even if other authentication methods would normally disable it. When negotiation is skipped, authentication concerns don't apply, so HTTP/2 should be allowed.

Changes Required

1. Update the condition that sets allowHttp2 = false to check if negotiation is being skipped
2. When SkipNegotiation = true, allow HTTP/2 connections regardless of authentication configuration

Test Case

The fix should allow this code to work without throwing an exception:

await using var connection = new HubConnectionBuilder()
    .WithUrl("http://localhost:5001/hub/hello", options =>
    {
        options.SkipNegotiation = true;
        options.Transports = HttpTransportType.WebSockets;
        options.WebSocketConfiguration = clientWebSocketOptions =>
        {
            clientWebSocketOptions.HttpVersion = HttpVersion.Version20;
            clientWebSocketOptions.HttpVersionPolicy = HttpVersionPolicy.RequestVersionOrLower;
        };
    })
    .Build();

await connection.StartAsync();

Related Issue

Fixes dotnet#59303

This pull request was created as a result of the following prompt from Copilot chat.

Problem

SignalR client throws an exception when trying to connect to HTTP/2 servers with SkipNegotiation = true:

An HttpMessageInvoker instance must be passed to ConnectAsync when using HTTP/2. (Parameter 'options')

Root Cause

In WebSocketsTransport.DefaultWebSocketFactory, the allowHttp2 variable is set to false when authentication methods like Negotiate Auth are used. However, this logic doesn't account for scenarios where SkipNegotiation = true, which bypasses the authentication negotiation entirely.

When allowHttp2 = false, the code path that passes the HttpClient as an invoker to ConnectAsync is skipped, causing the HTTP/2 connection to fail.

Solution

Modify the logic in DefaultWebSocketFactory to allow HTTP/2 when SkipNegotiation = true, even if other authentication methods would normally disable it. When negotiation is skipped, authentication concerns don't apply, so HTTP/2 should be allowed.

Changes Required

1. Update the condition that sets allowHttp2 = false to check if negotiation is being skipped
2. When SkipNegotiation = true, allow HTTP/2 connections regardless of authentication configuration

Test Case

The fix should allow this code to work without throwing an exception:

await using var connection = new HubConnectionBuilder()
    .WithUrl("http://localhost:5001/hub/hello", options =>
    {
        options.SkipNegotiation = true;
        options.Transports = HttpTransportType.WebSockets;
        options.WebSocketConfiguration = clientWebSocketOptions =>
        {
            clientWebSocketOptions.HttpVersion = HttpVersion.Version20;
            clientWebSocketOptions.HttpVersionPolicy = HttpVersionPolicy.RequestVersionOrLower;
        };
    })
    .Build();

await connection.StartAsync();

Related Issue

Fixes dotnet#59303

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