Ansible playbook not working when using roles in playbook

Question

So, my playbook works fine when using this syntax:

---
- hosts: all
  become: true
  become_user: root
  gather_facts: false
  connection: local
  vars_files:
    - roles/docker_setup/vars/docker_vars.yml
    - roles/docker_setup/vars/aws_cred.yml
  vars:
    instance_ids:
      - "i-xxxxxxxxxxx"
  tasks:
    - include_role:
        name: docker_setup
        tasks_from: docker_tasks.yml

But I read that you can use this syntax which looks much easier to handle once I want to add new roles to the playbook:

---
- hosts: all
  become: true
  become_user: root
  gather_facts: false
  connection: local
  vars_files:
    - roles/docker_setup/vars/docker_vars.yml
    - roles/docker_setup/vars/aws_cred.yml
  vars:
    instance_ids:
      - "i-xxxxxxxxxxx"
  roles:
  - docker_setup

The difference is:

roles:
  - docker_setup

instead of

tasks:
  - include_role:
      name: docker_setup
      tasks_from: docker_tasks.yml

But once I try to run the playbook nothing happens:

sudo ansible-playbook docker_setup.yml --ask-vault-pass -i hosts --user devops --key-file /home/devops/.ssh/id_rsa
Vault password: 

PLAY [all] *************************************************************************************************************************************************

PLAY RECAP *************************************************************************************************************************************************

Why is it that? Here is my tree of roles:

.
├── docker_setup
│   ├── handlers
│   │   └── main.yml
│   ├── tasks
│   │   └── docker_tasks.yml
│   └── vars
│       ├── aws_cred.yml
│       └── docker_vars.yml
└── user_host_create
    ├── handlers
    │   └── user_handlers.yml
    ├── tasks
    │   └── user_tasks.yml
    └── vars
        ├── user_password_vault.txt
        ├── user_password.yml
        └── user_vars.yml

and hosts file:

[webservers]
172.31.31.223

Thank you!

Answer 1

The difference between the two options below is what file with the tasks is executed.

  tasks:
    - include_role:
        name: docker_setup
        tasks_from: docker_tasks.yml

  roles:
    - docker_setup

In the first case, it is explicitly roles/docker_setup/tasks/docker_tasks.yml (see tasks_from).

In the second case, it is roles/docker_setup/tasks/main.yml (see Role directory structure). This file is missing in the role. As a result, nothing is executed. You can fix it and create the file e.g.

shell> cat roles/docker_setup/tasks/main.yml
- ansible.builtin.import_tasks: docker_tasks.yml

This would make the two options equivalent as to what tasks are executed. However, there will be other differences e.g. the scope of the variables, or inheritance of the tags. For details see Using Roles.