Bug Report: Trying to resolve a dictionary key from an empty list

[Rylon]

Issue Type
Bug Report

Ansible Version
ansible 1.9.1
configured module search path = None

Environment
Running from Mac OS X 10.10.3, managing Ubuntu 14.04 LTS.

Summary
Using with_items and an empty list, the task fails if the list is expected to contain dictionaries, which you try to lookup by key.

Steps To Reproduce
Consider this task:

- name: Install custom Elasticsearch plugins
  command:    /usr/share/elasticsearch/bin/plugin --install {{ item.name }} creates="/usr/share/elasticsearch/plugins/{{ item.installs_to }}"
  with_items: elasticsearch_plugins

When the elasticsearch_plugins variable is not defined, or is defined as an empty list ([]), I would expect the entire task to be skipped, however it looks like maybe Ansible is still trying to lookup the name key from item, which won't exist if the list is empty, and this results in the following failure:

fatal: [ubuntu_trusty] => One or more undefined variables: 'unicode object' has no attribute 'name'

When elasticsearch_plugins is defined as follows, this task works normally:

elasticsearch_plugins:
  - name:        "mobz/elasticsearch-head"
    installs_to: "head"

Expected Results
When the elasticsearch_plugins variable is an empty list, this task should be skipped, without attempting to lookup item.name or item.installs_to.

Actual Results
The task fails, with the following error:

fatal: [ubuntu_trusty] => One or more undefined variables: 'unicode object' has no attribute 'name'

[mightydok]

@bcoca skiping task is correct behaviour for empy iterator?

[bcoca]

@mightydok yes, with_ should skip if given None/Empty list

[jimi-c]

In the current devel branch, an empty list does result in a skipped task:

# ansible-playbook -vv 10920.yml -e elasticsearch_plugins=[]
Using /etc/ansible/ansible.cfg as config file
1 plays in 10920.yml
PLAY: ***************************************************************************
TASK [iterate over an non-existent variable] ************************************
ok: [localhost] => {"changed": false, "results": [], "skipped": true, "skipped_reason": "No items in the list"}
PLAY RECAP **********************************************************************
localhost                  : ok=1    changed=0    unreachable=0    failed=0   

Dealing with a non-existent variable is a bit more complex, since we have traditionally allowed bare-variables in with_* loops, however we have discussed deprecating that in favor of forcing something like with_item: "{{foo}}" instead, to make it clear that there is a variable there and not a string.

Per our normal policy, we close bug report issues when we see the issue has been corrected in the devel branch, so we will close this issue now.

If you continue seeing any problems related to this issue, or if you have any further questions, please let us know by stopping by one of the two mailing lists, as appropriate:

• https://groups.google.com/forum/#!forum/ansible-project - for user questions, tips, and tricks
• https://groups.google.com/forum/#!forum/ansible-devel - for strategy, future planning, and questions about writing code

Because this project is very active, we're unlikely to see comments made on closed tickets, but the mailing list is a great way to ask questions, or post if you don't think this particular issue is resolved.

Thank you!

[Rylon]

@jimi-c thanks! I'm not 100% familiar with the development process, but what sort of time period are we talking about for going from current devel branch into a release?

[jimi-c]

@Rylon we're looking at releasing an official 2.0 beta in early August. Major releases are generally done every three months, however we're going a bit slower with 2.0 as it is a fairly major change.

[Rylon]

@jimi-c Sounds great, thanks :)