WebSocket upgrade of HTTPS connection errors are uninformative

[adam-fowler]

Expected behavior

When a client is attempting to upgrade an HTTPS connection to a WebSocket connection and the TLS connection fails the returned error should indicate the TLS connection failed.

Actual behavior

The error returned is ChannelError.inappropriateOperationForState which is not very informative

Steps to reproduce

This issue is actually common to any ChannelHandler placed in front of the Upgrade ChannelHandler. So the following method provides an easier replication.

• Using the websocket server and client examples
• Write a channel handler that fires an error as soon as channelRead is called and closes the channel.
• Add it before the upgrade channel handler in the client.
• Run and watch the ChannelError.inappropriateOperationForState get returned and not the error returned by the above channel handler.

SwiftNIO version/commit hash

2.81.0

System & version information

swift-driver version: 1.120.5 Apple Swift version 6.1 (swiftlang-6.1.0.110.21 clang-1700.0.13.3)
Target: arm64-apple-macosx15.0

[adam-fowler]

Would it be appropriate for NIOTypedHTTPClientProtocolUpgrader to include the following

    public func errorCaught(context: ChannelHandlerContext, error: any Error) {
        self.upgradeResultPromise.fail(error)
    }

[Lukasa]

Yeah, that sounds like it absolutely would be appropriate. Very good suggestion @adam-fowler.

[adam-fowler]

#3210