include_tasks and noop

[Omar]

This is potential feature idea.

I'm developing a small collection and as an extension points I expose various variable that refer to 'task files'. For example, I have a role named prepare with a task file named `_yum.yml` and I have a variable `repositories_tasks` with a default value `_yum.yml`.

Users can override the variable `repositories_tasks` and provide their own tasks file. Or they could disable it entirely by providing an empty tasks file(maybe with a debug task).

`repositories_tasks: noop.yml`

Another case is for 'hooks' to run tasks at various phases in a role's execution. For example a `pre_upgrade_hook` or a `pre_restart hook` and have them undefined or set to `None` or an empty string. Sample code:

```

- include_tasks: "{{ pre_kubelet_upgrade_hook }}"

when: pre_kubelet_upgrade_hook is defined and (not pre_kubelet_upgrade_hook is none) and (pre_kubelet_upgrade_hook | trim != '')

```

After seeing this pattern I thought that this could br a lot simpler(from a user perspective). Suppose we have a special value that when it appears as a value in `include_tasks` nothing happens. I will use `ansible_noop` as the special value. the following:

- include_tasks: ansible_noop

simply does nothing.

When I user wants to disable a set tasks exposed through a variable, they can assign it to `ansible_noop`, and as a default value for all hook variables you can assign them to `ansible_noop`.

Sample code for role author:

`defaults/main.yml`

pre_kubelet_upgrade_hook: ansible_noop

update_kube_tasks: _update_kube.yml

copy_config_tasks: _copy_config.yml

Sample code for role clients:

include_role:

name: upgrade

vars:

  pre_kubelet_upgrade_hook: cri_upgrade.yml # File supplied by user

  update_kube_tasks: update_kube.yml

  copy_config_tasks: ansible_noop

What do you think?

[flowerysong]

I don't see any benefit to the proposed feature. If you want to skip an include based on a flag value, you can do that without adding complexity to the engine.

- include_tasks: "{{ task_file }}.yml"

  when: task_file | default('noop') != 'noop'