to_json not working on variable

[Dane Lipscombe]

When running ansible v1.8.2, in the below playbook, to_json fails to handle a basic variable

- name: a play that runs entirely on the ansible host

  hosts: localhost

  vars:

     users:

       - bob

       - joe

  tasks:

    # no problem

    - debug: msg="{{users|to_yaml}}"

    # ERROR: an unexpected type error occurred. Error was Undefined is not JSON serializable

    - debug: msg="{{users|to_json}}"

[Dane Lipscombe]

Could somebody please verify weather or not its just my problem? 

[Brian Coca]

I can confirm this, even threw in:
- debug: var=users
which works fine but still error out on your last task


--
Brian Coca

[Brian Coca]

very weird, the following works:

- debug: msg="{{users|default('la')|to_json}}"

--
Brian Coca