Why `Job::join` does not resume when coroutine is ...

# coroutines

[marcinmoskala]

Why Job::join does not resume when coroutine is just done? The documentation suggests that it should, but I cannot make in resume any other way but by crashing or cancelling a coroutine.

import kotlinx.coroutines.*

fun main(): Unit = runBlocking {
    val job = Job()
    launch(job) {
        delay(200)
    }
    job.join()
}
// Runs forever

[Nick Allen]

launch creates a new child Job, which it gives you as the return value. The child Job is finishing but the parent that you create explicitly is never finishing. Try just joining on the Job that launch returns or call complete on the Job you created.

[ephemient]

the job you explicitly created isn't complete just because one child is complete. you can still launch another coroutine in it, for example.

[louiscad]

You broke structured concurrency, that's why. Tip: don't inject jobs into coroutines manually to avoid that.

You probably want to use coroutineScope { } or call join() on the Job instance returned by the launch { } call.

[marcinmoskala]

That makes sense, thank you.