install nvm not idempotent?

[strarsis]

Each time I re-apply the playbook (after its successful aplication),
the install nvm task still runs each time - and takes a considerable amount of time to finish:
[...]
TASK [leonidas.nvm : Install nvm]
[...]
Is this task not idempotent? Or should it check nvm version before downloading things?

[Wtower]

Idempotence is not relevant with the amount of time to execute.

Idempotence is the property of certain operations in mathematics and computer science, that can be applied multiple times without changing the result beyond the initial application.

Source

Other useful links: Ansible glossary

You can confirm that the task is idempotent if ansible reports it as changed after running it consecutively with no other changes in between:

Run 1:

TASK [ansible-nvm : Install 0.10] **********************************************
changed: [default]

Run 2:

TASK [ansible-nvm : Install 0.10] **********************************************
ok: [default]

If you run the command manually nvm reports that version is already installed.

[Wtower]

After further investigation, it appers that recent nvm versions output the 'already installed' message in stderr rather than stdout, therefore the relevant task indeed does not accurately check with changed_when. I will fix that after some pending changes.