Ansible with-items auto flatten list of lists

Ansible has with_items directive, which make task iterating the lists in with_items. A normal usage is like

- name: copy file
  copy: src={{ item }} dest=/root/.ssh/{{ item }}
  with_items:
    - id_rsa
    - id_rsa.pub

But if you use list of lists, it will not work as your expect.

- name: copy file
  copy: src={{ item.0 }} dest=/root/.ssh/{{ item.1 }}
  with_items:
    - [ id_rsa, id_rsa_foo ]
    - [ id_rsa.pub, rd_rsa_foo.pub ]

Ansible will flatten the lists just like what with_flatten does. As a result, it will work like

- name: copy file
  copy: src={{ item.0 }} dest=/root/.ssh/{{ item.1 }}
  with_items:
    - id_rsa
    - id_rsa_foo
    - id_rsa.pub
    - id_rsa_foo.pub

This is not what we want, of curse. The workaround is wrapping the list of lists. like:

- name: copy file
  copy: src={{ item.0 }} dest=/root/.ssh/{{ item.1 }}
  with_items:
    -
      - [ id_rsa, id_rsa_foo ]
      - [ id_rsa.pub, rd_rsa_foo.pub ]

This is a historical issue rather than a bug. Here is the related ansible bug[0] and doc fix[1].

• [0] https://github.com/ansible/ansible/issues/5913
• [1] https://github.com/ko-zu/ansible/commit/0a1a5cde86df0424441b78dd9e67b96159cfd70f