Sendability warnings for ByteToMessage and MessageToBytes Handlers due to changes in addHandlers method.

[flexlixrup]

Expected behavior

No concurrency warnings in addHandlers method with ByteToMessage and MessageToByte handlers.

Actual behavior

Adding these handlers to a channel pipeline produces warnings.

Steps to reproduce

1. Compile pulsar-client-swift with NIO 2.77.0
2. You see no warnings regarding sendability
3. Compile again with NIO 2.78.0
4. See the warnings

If possible, minimal yet complete reproducer code (or URL to code)

https://github.com/flexlixrup/pulsar-client-swift/blob/1c93824e422ceb9343a632fec2c0258fdc6a5908/Sources/Pulsar/PulsarClient/PulsarClient.swift#L91-L94

In this example you can see where the warnings happens. addHandlers method now requires the PipelineHandlers to be sendable. But these handlers forbid conformance to sendable.

@available(*, unavailable)
extension ByteToMessageHandler: Sendable {}

SwiftNIO version/commit hash

NIO 2.78.0, the issue is due to 1e4fde1

System & version information

swift-driver version: 1.115.1 Apple Swift version 6.0.3 (swiftlang-6.0.3.1.10 clang-1600.0.30.1) Target: arm64-apple-macosx15.0

[Lukasa]

This is intentional. The pipeline modification method you’re using actually sends these handlers across concurrency domains, so the concern is warranted. If you’re on the event loop already, which you are in that context, use channel.pipeline.syncOperations.addHandlers, which will not warn.