when conditional evaluating to false, undefined dict variables in with_items receive error

[dylanjw]

Issue Type: Bug Report
Ansible Version: ansible 2.0.0
Ansible Configuration: clean
Environment: Fedora 22

Summary:
Variables in with_items are checked with when statement evaluating to false.

Steps To Reproduce:

With INSTANCE_CREATION set to false, i get an error with this part of a playbook:

  - name: launch test and DB ec2 instances
      ec2:
        key_name:           "{{ AWS_SSH_KEY_NAME }}"
        instance_type:      "{{ WEBTIER_INSTANCE_TYPE }}"
        image:              "{{ AWS_BASE_IMAGE }}"
        instance_tags:
            Name:           "{{ IMAGE_NAME }}-testdb"
        count_tag:
            Name:           "{{ IMAGE_NAME }}-testdb"
        exact_count:        2
        wait:               true
        group:              "{{ AWS_SG_NAME }}"
        vpc_subnet_id:      "{{ vpc.subnets[0].id }}"
        assign_public_ip:   true
        region:             "{{ REGION }}"
        volumes:
          - device_name: /dev/sda1
            device_type: gp2
            volume_size: 32 
            delete_on_termination: true
      register: ec2test_instances
      when: INSTANCE_CREATION

    - name: launch apphost ec2 instances
      ec2:
        key_name:           "{{ AWS_SSH_KEY_NAME }}"
        instance_type:      "{{ WEBTIER_INSTANCE_TYPE }}"
        image:              "{{ AWS_BASE_IMAGE }}"
        instance_tags:
            Name:           "{{ IMAGE_NAME }}-apphost"
        count_tag:
            Name:           "{{ IMAGE_NAME }}-apphost"
        exact_count:        1
        wait:               true
        group:              "{{ AWS_SG_NAME }}"
        vpc_subnet_id:      "{{ vpc.subnets[0].id }}"
        assign_public_ip:   true
        instance_profile_name: ec2s3
        region:             "{{ REGION }}"
        volumes:
          - device_name: /dev/sda1
            device_type: gp2
            volume_size: 32 
      register: ec2apphost_instance
      when: INSTANCE_CREATION

    - name: add all instances to ec2-hosts group
      add_host:
          hostname:         "{{ item.public_ip }}"
          groupname:        ec2-hosts
      with_items: ec2test_instances.tagged_instances + ec2apphost_instance.tagged_instances
      when: INSTANCE_CREATION

Expected Results:
When INSTANCE_CREATION is false the variables ec2test_instances and
ec2apphost_instance wont get registered and the "add all instances to ec2-host group" task should be skipped without error.

Actual Results:

I receive the following error:

TASK [launch test and DB ec2 instances] ****************************************
skipping: [localhost] => {"changed": false, "skip_reason": "Conditional check failed", "skipped": true}

TASK [launch apphost ec2 instances] ********************************************
skipping: [localhost] => {"changed": false, "skip_reason": "Conditional check failed", "skipped": true}

TASK [add all instances to ec2-hosts group] ************************************
An exception occurred during task execution. The full traceback is:
Traceback (most recent call last):
File "/usr/lib/python2.7/site-packages/ansible/executor/process/worker.py", line 118, in run
executor_result = TaskExecutor(host, task, job_vars, new_play_context, self._new_stdin, self._loader, shared_loader_obj).run()
File "/usr/lib/python2.7/site-packages/ansible/executor/task_executor.py", line 86, in run
items = self._get_loop_items()
File "/usr/lib/python2.7/site-packages/ansible/executor/task_executor.py", line 156, in _get_loop_items
loop_terms = listify_lookup_plugin_terms(terms=self._task.loop_args, templar=templar, loader=self._loader, fail_on_undefined=True)
File "/usr/lib/python2.7/site-packages/ansible/utils/listify.py", line 34, in listify_lookup_plugin_terms
terms = templar.template(terms, convert_bare=True, fail_on_undefined=fail_on_undefined)
File "/usr/lib/python2.7/site-packages/ansible/template/__init__.py", line 191, in template
result = self._do_template(variable, preserve_trailing_newlines=preserve_trailing_newlines, fail_on_undefined=fail_on_undefined, overrides=overrides)
File "/usr/lib/python2.7/site-packages/ansible/template/__init__.py", line 314, in _do_template
res = j2_concat(rf)
File "<template>", line 9, in root
File "/usr/lib/python2.7/site-packages/jinja2/runtime.py", line 489, in _fail_with_undefined_error
raise self._undefined_exception(hint)
UndefinedError: 'dict object' has no attribute 'tagged_instances'

fatal: [localhost]: FAILED! => {"failed": true, "stdout": ""}

PLAY RECAP *********************************************************************
localhost                  : ok=3    changed=0    unreachable=0    failed=1

[bcoca]

Possible Misunderstanding

Hi!

Thanks very much for your submission to Ansible. It sincerely means a lot to us.

We believe the ticket you have filed is being somewhat misunderstood, as one thing works a little differently than stated.

• when is evaluated for each item withing an with_ loop, so you cannot use when: false to shortcut undefineds in a with_ .
• use the default filter to make sure with_ is always correct.

In the future, this might be a topic more well suited for the user list, which you can also post here if you'd like some more help with the above.

• https://groups.google.com/forum/#!forum/ansible-project

Thank you once again for this and your interest in Ansible!