docker_image hack

main.yml

- name: Ensure an image has been built
  hosts: main
  vars:
    image: joshuaconner/someimage
    tag: sometag
  tasks:
    - name: Check if image has already been built using some fancy grep
      shell: if [ -z "$(docker images | grep '{{ image }}[[:blank:]]*{{ tag }}')" ]; then echo image not built; else echo image built; fi
      register: cmd_docker_images_grepped
      changed_when: cmd_docker_images_grepped.stdout != 'image built'

    - name: Ensure Docker image has been built
      command: docker pull {{ image }}:{{ tag }}
      when: cmd_docker_images_grepped.changed