fix: potential hanging edge case (#57)

a_sync/primitives/locks/prio_semaphore.py

@@ -40,6 +40,8 @@ def __init__(self, value: int = 1, *, name: Optional[str] = None) -> None:
         self._capacity = value
         super().__init__(value, name=name)
         self._waiters = []
+        # NOTE: This should (hopefully) be temporary
+        self._potential_lost_waiters = []
 
     def __repr__(self) -> str:
         return f"<{self.__class__.__name__} name={self.name} capacity={self._capacity} value={self._value} waiters={[manager._repr_no_parent_() for manager in self._waiters]}>"
@@ -85,9 +87,10 @@ def _wake_up_next(self) -> None:
 
             while manager._waiters:
                 waiter = manager._waiters.popleft()
+                waiter = self._potential_lost_waiters.remove(waiter)
                 if not waiter.done():
                     waiter.set_result(None)
-                    logger.debug(f"woke up %s", waiter)
+                    logger.debug("woke up %s", waiter)
                     woke_up = True
                     break
 
@@ -106,6 +109,15 @@ def _wake_up_next(self) -> None:
                 # There are no more waiters, get rid of the empty manager
                 self._context_managers.pop(manager._priority)
             return
+
+        # emergency procedure (hopefully temporary): 
+        while self._potential_lost_waiters:
+            waiter = self._potential_lost_waiters.pop(0)
+            logger.debug('we found a lost waiter %s', waiter)
+            if not waiter.done():
+                waiter.set_result(None)
+                logger.warning("woke up lost waiter %s", waiter)
+                return
         logger.debug("%s has no waiters to wake", self)
 
 class _AbstractPrioritySemaphoreContextManager(Semaphore, Generic[PT]):
@@ -156,6 +168,7 @@ async def acquire(self) -> Literal[True]:
         while self._parent._value <= 0:
             fut = self.loop.create_future()
             self.waiters.append(fut)
+            self._parent._potential_lost_waiters.append(fut)
             try:
                 await fut
             except: