Fixed cancellation and added a few docstrings

giambio/_core.py

@@ -68,14 +68,12 @@ class AsyncScheduler:
                     except BaseException as error:
                         self.current_task.exc = error
                         self.reschedule_parent(self.current_task)
-                        raise  # Maybe find a better way to propagate errors?
             if self.selector.get_map():
                 try:
                     self.check_io()
                 except BaseException as error:
                     self.current_task.exc = error
                     self.reschedule_parent(self.current_task)
-                    raise  # Maybe find a better way to propagate errors?
             while self.tasks:    # While there are tasks to run
                 self.current_task = self.tasks.popleft()  # Sets the currently running task
                 try:
@@ -97,7 +95,6 @@ class AsyncScheduler:
                 except BaseException as error:    # Coroutine raised
                     self.current_task.exc = error
                     self.reschedule_parent(self.current_task)
-                    raise  # Maybe find a better way to propagate errors?
 
     def check_events(self):
         """Checks for ready or expired events and triggers them"""
@@ -206,10 +203,18 @@ class AsyncScheduler:
         coroutine returns or, if an exception gets raised, the exception will get propagated inside the
         parent task"""
 
-        if child not in self.joined:
-            self.joined[child] = self.current_task
+        if child.cancelled:  # Task was cancelled and is therefore dead
+            self.tasks.append(self.current_task)
+        elif child.exc:     # Task raised an error, propagate it!
+            self.reschedule_parent(child)
+            raise child.exc
+        elif child.finished:
+            self.tasks.append(self.current_task)  # Task has already finished
         else:
-            raise AlreadyJoinedError("Joining the same task multiple times is not allowed!")
+            if child not in self.joined:
+                self.joined[child] = self.current_task
+            else:
+                raise AlreadyJoinedError("Joining the same task multiple times is not allowed!")
 
     def sleep(self, seconds: int or float):
         """Puts the caller to sleep for a given amount of seconds"""

giambio/_traps.py

@@ -14,7 +14,10 @@ See the License for the specific language governing permissions and
 limitations under the License.
 """
 
-"""Helper methods to interact with the event loop"""
+# Helper methods to interact with the event loop
+# These coroutines are the one and only way to interact
+# with the event loop from the user's perspective, and
+# the entire library is based on these traps
 
 import types
 import socket
@@ -47,7 +50,8 @@ def join(task):
         :type task: class: Task
     """
 
-    yield "join", task
+    res = yield "join", task
+    return task.result
 
 
 @types.coroutine
@@ -89,12 +93,19 @@ def want_write(sock: socket.socket):
 
 @types.coroutine
 def event_set(event, value):
+    """Communicates to the loop that the given event object
+       must be set. This is important as the loop constantly
+       checks for active events to deliver them
+    """
 
     yield "event_set", event, value
 
 
 @types.coroutine
 def event_wait(event):
+    """Notifies the event loop that the current task has to wait
+       for the event to trigger
+    """
 
     msg = yield "event_wait", event
     return msg

tests/count.py

@@ -7,7 +7,7 @@ async def countdown(n: int):
         n -= 1
         await giambio.sleep(1)
     print("Countdown over")
-
+    return 0
 
 async def countup(stop: int, step: int = 1):
     x = 0
@@ -16,6 +16,7 @@ async def countup(stop: int, step: int = 1):
         x += 1
         await giambio.sleep(step)
     print("Countup over")
+    return 1
 
 
 async def main():
@@ -24,10 +25,11 @@ async def main():
     print("Counters started, awaiting completion")
     await giambio.sleep(2)
     print("Slept 2 seconds, killing countup")
-    await cup.cancel()    ## DOES NOT WORK!!!
+    await cup.cancel()
     print("Countup cancelled")
-    await cup.join()
-    await cdown.join()
+    up = await cup.join()
+    down = await cdown.join()
+    print(f"Countup returned: {up}\nCountdown returned: {down}")
     print("Task execution complete")
 
 if __name__ == "__main__":