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# no-changed-when
This rule checks that tasks return changes to results or conditions. Unless
tasks only read information, you should ensure that they return changes in the
following ways:
- Register results or conditions and use the `changed_when` clause.
- Use the `creates` or `removes` argument.
You should always use the `changed_when` clause on tasks that do not naturally
detect if a change has occurred or not. Some of the most common examples are
[shell] and [command] modules, which run arbitrary commands.
One very common workaround is to use a boolean value like `changed_when: false`
if the task never changes anything or `changed_when: true` if it always changes
something, but you can also use any expressions, including ones that use the
registered result of a task, like in our example below.
This rule also applies to handlers, not only to tasks because they are also
tasks.
## Problematic Code
```yaml
---
- name: Example playbook
hosts: localhost
tasks:
- name: Does not handle any output or return codes
ansible.builtin.command: cat {{ my_file | quote }} # <- Does not handle the command output.
```
## Correct Code
```yaml
---
- name: Example playbook
hosts: localhost
tasks:
- name: Handle shell output with return code
ansible.builtin.command: cat {{ my_file | quote }}
register: my_output # <- Registers the command output.
changed_when: my_output.rc != 0 # <- Uses the return code to define when the task has changed.
```
[shell]:
https://docs.ansible.com/ansible/latest/collections/ansible/builtin/shell_module.html
[command]:
https://docs.ansible.com/ansible/latest/collections/ansible/builtin/command_module.html
|
