<@U2E974ELT> Would you be interested in this contribution? ``` public suspend inline fun &lt;T : Clo...

# coroutines

[SUPERCILEX]

@elizarov Would you be interested in this contribution?

public suspend inline fun <T : Closeable?, R> T.useCancellably(
        crossinline block: (T) -> R
): R = suspendCancellableCoroutine { cont ->
    cont.invokeOnCancellation { this?.close() }
    use(block)
}

[elizarov]

What is the use-case?

[SUPERCILEX]

For any blocking java work

[elizarov]

What kind of blocking java work? Example?

[SUPERCILEX]

Example:

runBlocking {
        val foo = launch(<http://Dispatchers.IO|Dispatchers.IO>) {
            ServerSocket(PORT).useCancellably {
                it.accept()
                // ...
            }
        }

        delay(100)

        print("Cancelling")
        foo.cancel()
    }

[SUPERCILEX]

Or anything with Scanner

[elizarov]

Why would use blocking scokets with coroutines?

[elizarov]

What’s wrong with a regular use inside a coroutine? I don’t see why you need a special function.

[SUPERCILEX]

TBH, that was just a playground

[SUPERCILEX]

But the issue is that without that function, calling cancel doesn't do anything

[SUPERCILEX]

With useCancellably, it throws an exception and aborts the connection attempt

[SUPERCILEX]

That's also relevant for raw URL streams

[SUPERCILEX]

And any other Java stream

[SUPERCILEX]

Current cancellability is confusing because nothing happens since the blocking work just keeps blocking indefinitely

[SUPERCILEX]

isActive is only useful for computational work

[elizarov]

I see the point. The only problem is that is it a very dangerous thing to give to users in a lib. Many blocking closeable things in Java cannot be concurrently closed (example: JDBC connections) and by trying to close them concurrently you’ll just make it worse

[elizarov]

I’ll leave it to people who know what they are actually doing and they can write this function for themselves

[SUPERCILEX]

Do you think it would be worth showing in the docs?

[SUPERCILEX]

With associated caveats

[elizarov]

I don’t know. Our docs are already too large. They need more simpler examples and explanations for basic concepts.

[SUPERCILEX]

Yeah, that's true 😆 😭

[SUPERCILEX]

I think I'll just write a short Medium post or something