Last handler with same name wins for listen too (#81358)

Fixes #49371
Fixes #81013

changelogs/fragments/81013-handlers-listen-last-defined-only.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - handlers - the ``listen`` keyword can affect only one handler with the same name, the last one defined as it is a case with the ``notify`` keyword (https://github.com/ansible/ansible/issues/81013)

lib/ansible/plugins/strategy/__init__.py

@@ -509,8 +509,11 @@ class StrategyBase:
 
     def search_handlers_by_notification(self, notification: str, iterator: PlayIterator) -> t.Generator[Handler, None, None]:
         templar = Templar(None)
+        handlers = [h for b in reversed(iterator._play.handlers) for h in b.block]
         # iterate in reversed order since last handler loaded with the same name wins
-        for handler in (h for b in reversed(iterator._play.handlers) for h in b.block if h.name):
+        for handler in handlers:
+            if not handler.name:
+                continue
             if not handler.cached_name:
                 if templar.is_template(handler.name):
                     templar.available_variables = self._variable_manager.get_vars(
@@ -548,7 +551,8 @@ class StrategyBase:
                 break
 
         templar.available_variables = {}
-        for handler in (h for b in iterator._play.handlers for h in b.block):
+        seen = []
+        for handler in handlers:
             if listeners := handler.listen:
                 if notification in handler.get_validated_value(
                     'listen',
@@ -556,6 +560,9 @@ class StrategyBase:
                     listeners,
                     templar,
                 ):
+                    if handler.name and handler.name in seen:
+                        continue
+                    seen.append(handler.name)
                     yield handler
 
     @debug_closure

test/integration/targets/handlers/roles/test_listen_role_dedup_global/handlers/main.yml

@@ -0,0 +1,4 @@
+- name: role_handler
+  debug:
+    msg: "a handler from a role"
+  listen: role_handler

test/integration/targets/handlers/roles/test_listen_role_dedup_role1/meta/main.yml

@@ -0,0 +1,2 @@
+dependencies:
+  - test_listen_role_dedup_global

test/integration/targets/handlers/roles/test_listen_role_dedup_role1/tasks/main.yml

@@ -0,0 +1,3 @@
+- name: a task from role1
+  command: echo
+  notify: role_handler

test/integration/targets/handlers/roles/test_listen_role_dedup_role2/meta/main.yml

@@ -0,0 +1,2 @@
+dependencies:
+  - test_listen_role_dedup_global

test/integration/targets/handlers/roles/test_listen_role_dedup_role2/tasks/main.yml

@@ -0,0 +1,3 @@
+- name: a task from role2
+  command: echo
+  notify: role_handler

test/integration/targets/handlers/runme.sh

@@ -187,3 +187,6 @@ grep out.txt -e "ERROR! Using a block as a handler is not supported."
 
 ansible-playbook test_include_role_handler_once.yml -i inventory.handlers "$@" 2>&1 | tee out.txt
 [ "$(grep out.txt -ce 'handler ran')" = "1" ]
+
+ansible-playbook test_listen_role_dedup.yml "$@" 2>&1 | tee out.txt
+[ "$(grep out.txt -ce 'a handler from a role')" = "1" ]

test/integration/targets/handlers/test_listen_role_dedup.yml

@@ -0,0 +1,5 @@
+- hosts: localhost
+  gather_facts: false
+  roles:
+    - test_listen_role_dedup_role1
+    - test_listen_role_dedup_role2