Added some TODOs and tried a solution for the cancel() method (and failed)

experiment.py

@@ -28,21 +28,25 @@ async def countdown(n):
         print("countdown cancelled!")
 
 async def count(stop, step=1):
-    x = 0
-    while x < stop:
-        print(f"Up {x}")
-        x += step
-        await giambio.sleep(step)
-    print("Countup over")
-    return "Count UP over"
-
+    try:
+        x = 0
+        while x < stop:
+            print(f"Up {x}")
+            x += step
+            await giambio.sleep(step)
+        print("Countup over")
+        return "Count UP over"
+    except giambio.exceptions.CancelledError:
+        print("count cancelled!")
 
 async def main():
-    print("Spawning countdown immediately, scheduling count for 2 secs from now")
+    print("Spawning countdown immediately, scheduling count for 4 secs from now")
     task = loop.spawn(countdown(8))
-    task1 = loop.schedule(count(8, 2), 2)
+    task1 = loop.schedule(count(8, 2), 4)
+    await giambio.sleep(0)  # Beware! Cancelling a task straight away will propagate the error in the parent
+#    await task.cancel()    # TODO: Fix this to reschedule the parent task properly
     result = await task.join()
-    result1 = await task1.join()   # Joining a scheduled task does not reschedule the parent task
+    result1 = await task1.join()
     print(f"countdown returned: {result}\ncount returned: {result1}")
     print("All done")
 

giambio/core.py

@@ -51,6 +51,8 @@ class EventLoop:
                 except StopIteration as e:
                     self.running.result = Result(e.args[0] if e.args else None, None)  # Saves the return value
                     self.to_run.extend(self.joined.pop(self.running, ()))  # Reschedules the parent task
+                except RuntimeError:
+                    self.to_run.append(self.running)
                 except Exception as has_raised:
                     self.to_run.extend(self.joined.pop(self.running, ()))  # Reschedules the parent task
                     if self.running.joined:    # Let the join function handle the hassle of propagating the error
@@ -158,6 +160,7 @@ class Task:
         self.joined = False
         self.result = None   # Updated when the coroutine execution ends
         self.loop = loop  # The EventLoop object that spawned the task
+        self.cancelled = False
 
     def run(self):
         self.status = True
@@ -210,9 +213,10 @@ def want_write(sock: socket.socket):
 def join(task: Task):
     """'Tells' the scheduler that the desired task MUST be awaited for completion"""
 
-    task.joined = True
-    yield "want_join", task
-    return task.get_result()
+    if not task.cancelled:
+        task.joined = True
+        yield "want_join", task
+        return task.get_result()
 
 
 @types.coroutine