Ensure that `OwnCancelSchedule` flag will not be removed from `wait()` and `withTimeout()`. (#519)

chronos/internal/asyncfutures.nim

@@ -1410,6 +1410,8 @@ proc withTimeout*[T](fut: Future[T], timeout: Duration): Future[bool] {.
   var
     retFuture = newFuture[bool]("chronos.withTimeout",
                                 {FutureFlag.OwnCancelSchedule})
+      # We set `OwnCancelSchedule` flag, because we going to cancel `retFuture`
+      # manually at proper time.
     moment: Moment
     timer: TimerCallback
     timeouted = false
@@ -1536,6 +1538,8 @@ proc wait*[T](fut: Future[T], timeout = InfiniteDuration): Future[T] =
   ## should return, because it can't be cancelled too.
   var
     retFuture = newFuture[T]("chronos.wait()", {FutureFlag.OwnCancelSchedule})
+      # We set `OwnCancelSchedule` flag, because we going to cancel `retFuture`
+      # manually at proper time.
 
   waitImpl(fut, retFuture, timeout)
 
@@ -1677,6 +1681,8 @@ proc wait*(fut: InternalRaisesFuture, timeout = InfiniteDuration): auto =
     InternalRaisesFutureRaises = E.prepend(CancelledError, AsyncTimeoutError)
 
   let
-    retFuture = newFuture[T]("chronos.wait()", {FutureFlag.OwnCancelSchedule})
+    retFuture = newFuture[T]("chronos.wait()", {OwnCancelSchedule})
+      # We set `OwnCancelSchedule` flag, because we going to cancel `retFuture`
+      # manually at proper time.
 
   waitImpl(fut, retFuture, timeout)

tests/testfut.nim

@@ -1594,6 +1594,19 @@ suite "Future[T] behavior test suite":
     discard someFut.tryCancel()
     await someFut
 
+  asyncTest "wait() should allow cancellation test (depends on race())":
+    proc testFoo(): Future[bool] {.async.} =
+      let
+        resFut = sleepAsync(2.seconds).wait(3.seconds)
+        timeFut = sleepAsync(1.seconds)
+        cancelFut = cancelAndWait(resFut)
+      discard await race(cancelFut, timeFut)
+      if cancelFut.finished():
+        return (resFut.cancelled() and cancelFut.completed())
+      false
+
+    check (await testFoo()) == true
+
   asyncTest "withTimeout() cancellation undefined behavior test #1":
     proc testInnerFoo(fooFut: Future[void]): Future[TestFooConnection] {.
          async.} =
@@ -1654,6 +1667,19 @@ suite "Future[T] behavior test suite":
     discard someFut.tryCancel()
     await someFut
 
+  asyncTest "withTimeout() should allow cancellation test (depends on race())":
+    proc testFoo(): Future[bool] {.async.} =
+      let
+        resFut = sleepAsync(2.seconds).withTimeout(3.seconds)
+        timeFut = sleepAsync(1.seconds)
+        cancelFut = cancelAndWait(resFut)
+      discard await race(cancelFut, timeFut)
+      if cancelFut.finished():
+        return (resFut.cancelled() and cancelFut.completed())
+      false
+
+    check (await testFoo()) == true
+
   asyncTest "Cancellation behavior test":
     proc testInnerFoo(fooFut: Future[void]) {.async.} =
       await fooFut