Add Flows.usingChannel() for concurrent flow emission

[denyshorman]

Motivation

Jox Flow currently supports creating flows using Flows.usingEmit(), but it only works for single-threaded, sequential emission. The provided FlowEmit is thread-unsafe and cannot be shared across multiple threads.

For concurrent emission, users must manually create channels, handle cleanup, and forward elements to the flow – which is error-prone and verbose.

Solution

This PR introduces Flows.usingChannel(), which provides a thread-safe Sink for concurrent emission from multiple threads. This is equivalent to Kotlin Coroutines' channelFlow.

Kotlin vs Jox comparison:

• Kotlin flow {} ↔ Jox Flows.usingEmit()
• Kotlin channelFlow {} ↔ Jox Flows.usingChannel()

Example

var flow = Flows.usingChannel(sink -> 
    supervised(scope -> {
        scope.forkUser(() -> { sink.send(1); return null; });
        scope.forkUser(() -> { sink.send(2); return null; });
        return null;
    })
);

[adamw]

Thank you!

[denyshorman]

🤝

[adamw]

Released as 0.5.2