Alternately track listening handlers by uuid if no name is set

Fixes #17846

test/integration/targets/handlers/runme.sh

@@ -3,6 +3,7 @@
 set -eux
 
 ansible-playbook test_handlers.yml -i inventory.handlers -v "$@" --tags scenario1
+ansible-playbook test_listening_handlers.yml -i inventory.handlers -v "$@"
 
 [ "$(ansible-playbook test_handlers.yml -i inventory.handlers -v "$@" --tags scenario2 -l A \
 | egrep -o 'RUNNING HANDLER \[test_handlers : .*?]')" = "RUNNING HANDLER [test_handlers : test handler]" ]

test/integration/targets/handlers/test_handlers.yml

@@ -18,6 +18,31 @@
             - "'handler2_called' in hostvars[inventory_hostname]"
       tags: ['scenario1']
 
+- name: verify listening handlers
+  hosts: A
+  gather_facts: False
+  connection: local
+  tasks:
+    - name: notify some handlers
+      command: echo foo
+      notify:
+        - notify_listen
+  post_tasks:
+    - name: assert all defined handlers ran without error
+      assert:
+        that:
+        - "notify_listen_ran_1 is defined"
+        - "notify_listen_ran_2 is defined"
+  handlers:
+    - name: first listening handler has a name
+      set_fact:
+        notify_listen_ran_1: True
+      listen: notify_listen
+    # second listening handler does not
+    - set_fact:
+        notify_listen_ran_2: True
+      listen: notify_listen
+
 - name: test handlers
   hosts: testgroup
   gather_facts: False

test/integration/targets/handlers/test_listening_handlers.yml

@@ -0,0 +1,25 @@
+---
+- name: verify listening handlers
+  hosts: A
+  gather_facts: False
+  connection: local
+  tasks:
+    - name: notify some handlers
+      command: echo foo
+      notify:
+        - notify_listen
+  post_tasks:
+    - name: assert all defined handlers ran without error
+      assert:
+        that:
+        - "notify_listen_ran_1 is defined"
+        - "notify_listen_ran_2 is defined"
+  handlers:
+    - name: first listening handler has a name
+      set_fact:
+        notify_listen_ran_1: True
+      listen: notify_listen
+    # second listening handler does not
+    - set_fact:
+        notify_listen_ran_2: True
+      listen: notify_listen