Is there a way to access the current clock time in...

# coroutines

[Adecker]

Is there a way to access the current clock time in production (System.currentTimeMillis() or similar…) that is compatible with the virtual clock time in kotlinx-coroutines-test ? I found a reference to an older method that I don’t think will work since DelayController is deprecated, but I’m not able to find any methods to replace it.

[hfhbd]

Depending on your use-case you could use a TimeSource or a kotlinx-datetime Clock

[Adecker]

I suppose I’m wondering more if there’s a way to get that info from the coroutineContext without referencing TestCoroutineScheduler in production code. I’m currently passing in a parameter to provide the time, but it’s not the most convenient to pass it through multiple functions.

[hfhbd]

If you only want to inject it, you could either use a "real" di framework or use coroutineContext and inject it manually with your own class and key.

[Adecker]

The goal is to write a time oriented flow function that leverages the virtual clock during tests automatically. Injection is the bad/not-great solution, I was hoping for a solution that works in any coroutineContext without extra setup.

[hfhbd]

Could you provide your flow? You could also use delay in your flow

BTW I mean this:

@ExperimentalTime
class TimeSourceContext(timeSource: TimeSource): CoroutineContext.Element, TimeSource by timeSource {
  override val key: CoroutineContext.Key<TimeSourceContext> = TimeSourceContext
  companion object: CoroutineContext.Key<TimeSourceContext>
}
    
@Test
fun a() = runTest {
  withContext(TimeSourceContext(testTimeSource)) {
    val timeSource: TimeSource = coroutineContext[TimeSourceContext]!!
  }
}

[Adecker]

that would be great if it were a standard context element, but I don’t want to add hidden dependencies on the context the flow is collected in.

[hfhbd]

Hm, I see, yeah making the context itself a TimeSource would be nice too, to run measureTime or getting a TimeMark without di.

[CLOVIS]

A simple KotlinX.Datetime Clock implementation that uses the TestApplication context: https://gitlab.com/opensavvy/formulaide/-/blob/main/test/src/commonMain/kotlin/utils/TestClock.kt#L10

Your code:

fun foo(clock: Clock) {
    println(clock.now())
}

Production usage (or use your favorite DI lib):

foo(Clock.System)

Test usage:

@Test
fun testFoo() = runTest {
    foo(testClock())
}

[hfhbd]

Yeah, or this helper method to get a Clock from a TimeSource, like TestTimeSource too: https://kotlinlang.slack.com/archives/C01923PC6A0/p1671029931781309?thread_ts=1671020823.299299&channel=C01923PC6A0&message_ts=1671029931.781309

[hfhbd]

But you still need to pass the clock