CoroutineScope cancellation requires a Job

I expected a CoroutineScope to be cancellable on it’s own. But a Job must be specified for a CoroutineScope to be cancelled. This seems a bit odd and error-prone.

Example

The following fails with IllegalStateException: Scope should no longer be active:

val scope = CoroutineScope(dispatcher)
check(scope.isActive) { "Scope should be active" }

scope.coroutineContext.cancel()

check(!scope.coroutineContext.isActive) { "Dispatcher should no longer be active" }
check(!scope.isActive) { "Scope should no longer be active" } // fails here

But if you cancel via a job, no problems:

val job = Job()
val scope = CoroutineScope(dispatcher + job)
check(scope.isActive) { "Scope should be active" }

job.cancel()

check(!scope.coroutineContext.isActive) { "Dispatcher should no longer be active" }
check(!scope.isActive) { "Scope should no longer be active" }

[elizarov]

Nope. That was bad idea. We’ll create Job() if it is missing. This way, we’ll need no change to .isActive documentation either

[fvasco]

Should the documentation fixed?

isActive and coroutineContext.isActive have different behaviour, despite the documentation.