Ensure blockinfile correctly returns backupfile (#72544)

* Ensure blockinfile correctly returns backupfile

  Fixes #27626
  based on #27859

Co-authored-by: Giovanni Sciortino (@giovannisciortino)

changelogs/fragments/blockinfile_fix_no_backup_return.yml

@@ -0,0 +1,2 @@
+bugfixes:
+  - blockinfile now returns name of backup file when this option is used.

lib/ansible/modules/blockinfile.py

@@ -328,9 +328,10 @@ def main():
         msg = 'Block inserted'
         changed = True
 
+    backup_file = None
     if changed and not module.check_mode:
         if module.boolean(params['backup']) and path_exists:
-            module.backup_local(path)
+            backup_file = module.backup_local(path)
         # We should always follow symlinks so that we change the real file
         real_path = os.path.realpath(params['path'])
         write_changes(module, result, real_path)
@@ -345,7 +346,11 @@ def main():
     attr_diff['after_header'] = '%s (file attributes)' % path
 
     difflist = [diff, attr_diff]
-    module.exit_json(changed=changed, msg=msg, diff=difflist)
+
+    if backup_file is None:
+        module.exit_json(changed=changed, msg=msg, diff=difflist)
+    else:
+        module.exit_json(changed=changed, msg=msg, diff=difflist, backup_file=backup_file)
 
 
 if __name__ == '__main__':

test/integration/targets/blockinfile/tasks/add_block_to_existing_file.yml

@@ -12,6 +12,11 @@
     backup: yes
   register: blockinfile_test0
 
+- name: ensure we have a bcackup file
+  assert:
+    that:
+      - "'backup_file' in blockinfile_test0"
+
 - name: check content
   shell: 'grep -c -e "Match User ansible-agent" -e "PasswordAuthentication no" {{ output_dir_test }}/sshd_config'
   register: blockinfile_test0_grep