Lazy coroutine stays in DebugProbes output if never started

[timurstrekalov]

When a coroutine with start = CoroutineStart.LAZY is cancelled before ever starting, DebugProbes seems to keep them around forever.

Example:

import kotlinx.coroutines.*
import kotlinx.coroutines.debug.DebugProbes

object Main {

    @JvmStatic
    fun main(args: Array<String>): Unit = runBlocking {
        DebugProbes.enableCreationStackTraces = false
        DebugProbes.install()

        val job = launch(start = CoroutineStart.LAZY) {
            delay(Long.MAX_VALUE)
        }
        job.invokeOnCompletion { println("job stopped: ${it?.message}") }

        job.cancel("foo")
        job.join()

        DebugProbes.dumpCoroutines(System.out)
    }
}

Output:

job stopped: foo
Coroutines dump 2020/10/10 13:52:45

Coroutine LazyStandaloneCoroutine{Cancelled}@26b3fd41, state: CREATED
	(Coroutine creation stacktrace)
Process finished with exit code 0

Note that if that lazy job is ever started, it gets correctly removed.

Example with start = CoroutineStart.DEFAULT:

import kotlinx.coroutines.*
import kotlinx.coroutines.runBlocking

object Main {

    @JvmStatic
    fun main(args: Array<String>): Unit = runBlocking {
        DebugProbes.enableCreationStackTraces = false
        DebugProbes.install()

        val job = launch {
            delay(Long.MAX_VALUE)
        }
        job.invokeOnCompletion { println("job stopped: ${it?.message}") }

        job.cancel("foo")
        job.join()

        DebugProbes.dumpCoroutines(System.out)
    }
}

Output:

job stopped: foo
Coroutines dump 2020/10/10 13:52:29
Process finished with exit code 0