- hosts: localhost
  gather_facts: no
  tasks:
    - block:
      - name: Test nested undefined var fails, single node
        debug:
          msg: "{{ [{ 'key': nested_and_undefined }] }}"
        register: result
        ignore_errors: yes

      - assert:
          that:
            - "\"'nested_and_undefined' is undefined\" in result.msg"

      - name: Test nested undefined var fails, multiple nodes
        debug:
          msg: "{{ [{ 'key': nested_and_undefined}] }} second_node"
        register: result
        ignore_errors: yes

      - assert:
          that:
            - "\"'nested_and_undefined' is undefined\" in result.msg"