Allow for searching handler subdir for included task via include_role (#81733)

Fixes #81722

changelogs/fragments/81722-handler-subdir-include_tasks.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - Allow for searching handler subdir for included task via include_role (https://github.com/ansible/ansible/issues/81722)

lib/ansible/playbook/included_file.py

@@ -146,9 +146,12 @@ class IncludedFile:
                                     cumulative_path = parent_include_dir
                                 include_target = templar.template(include_result['include'])
                                 if original_task._role:
-                                    new_basedir = os.path.join(original_task._role._role_path, 'tasks', cumulative_path)
-                                    candidates = [loader.path_dwim_relative(original_task._role._role_path, 'tasks', include_target),
-                                                  loader.path_dwim_relative(new_basedir, 'tasks', include_target)]
+                                    dirname = 'handlers' if isinstance(original_task, Handler) else 'tasks'
+                                    new_basedir = os.path.join(original_task._role._role_path, dirname, cumulative_path)
+                                    candidates = [
+                                        loader.path_dwim_relative(original_task._role._role_path, dirname, include_target),
+                                        loader.path_dwim_relative(new_basedir, dirname, include_target)
+                                    ]
                                     for include_file in candidates:
                                         try:
                                             # may throw OSError

test/integration/targets/handlers/roles/include_role_include_tasks_handler/handlers/include_handlers.yml

@@ -0,0 +1,2 @@
+- debug:
+    msg: handler ran

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

@@ -0,0 +1,2 @@
+- name: handler
+  include_tasks: include_handlers.yml

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

@@ -0,0 +1,2 @@
+- command: echo
+  notify: handler

test/integration/targets/handlers/runme.sh

@@ -192,3 +192,6 @@ ansible-playbook test_listen_role_dedup.yml "$@" 2>&1 | tee out.txt
 [ "$(grep out.txt -ce 'a handler from a role')" = "1" ]
 
 ansible localhost -m include_role -a "name=r1-dep_chain-vars" "$@"
+
+ansible-playbook test_include_tasks_in_include_role.yml "$@" 2>&1 | tee out.txt
+[ "$(grep out.txt -ce 'handler ran')" = "1" ]

test/integration/targets/handlers/test_include_tasks_in_include_role.yml

@@ -0,0 +1,5 @@
+- hosts: localhost
+  gather_facts: false
+  tasks:
+    - include_role:
+        name: include_role_include_tasks_handler