Track notified handlers by object rather than simply their name

Due to the fact that roles may be instantiated with different sets of
params (multiple inclusions of the same role or via role dependencies),
simply tracking notified handlers by name does not work. This patch
changes the way we track handler notifications by using the handler
object itself instead of just the name, allowing for multiple internal
instances. Normally this would be bad, but we also modify the way we
search for handlers by first looking at the notifying tasks dependency
chain (ensuring that roles find their own handlers first) and then at
the main list of handlers, using the first match it finds.

This patch also modifies the way we setup the internal list of handlers,
which should allow us to correctly identify if a notified handler exists
more easily.

Fixes #15084

lib/ansible/executor/task_queue_manager.py

@@ -114,17 +114,20 @@ class TaskQueueManager:
         self._result_prc = ResultProcess(self._final_q, self._workers)
         self._result_prc.start()
 
-    def _initialize_notified_handlers(self, handlers):
+    def _initialize_notified_handlers(self, play):
         '''
         Clears and initializes the shared notified handlers dict with entries
         for each handler in the play, which is an empty array that will contain
         inventory hostnames for those hosts triggering the handler.
         '''
 
+        handlers = play.handlers
+        for role in play.roles:
+            handlers.extend(role._handler_blocks)
+
         # Zero the dictionary first by removing any entries there.
         # Proxied dicts don't support iteritems, so we have to use keys()
-        for key in self._notified_handlers.keys():
-            del self._notified_handlers[key]
+        self._notified_handlers.clear()
 
         def _process_block(b):
             temp_list = []
@@ -139,9 +142,10 @@ class TaskQueueManager:
         for handler_block in handlers:
             handler_list.extend(_process_block(handler_block))
 
-        # then initialize it with the handler names from the handler list
+        # then initialize it with the given handler list
         for handler in handler_list:
-            self._notified_handlers[handler.get_name()] = []
+            if handler not in self._notified_handlers:
+                self._notified_handlers[handler] = []
 
     def load_callbacks(self):
         '''
@@ -226,7 +230,7 @@ class TaskQueueManager:
         self.send_callback('v2_playbook_on_play_start', new_play)
 
         # initialize the shared dictionary containing the notified handlers
-        self._initialize_notified_handlers(new_play.handlers)
+        self._initialize_notified_handlers(new_play)
 
         # load the specified strategy (or the default linear one)
         strategy = strategy_loader.get(new_play.strategy, self)