Using a variable list for tags parameter results in an unhashable type: 'list' exception

[cnunemaker]

SUMMARY

Providing a variable list to the tags parameter results in the following error message:

ERROR! Unexpected Exception, this is probably a bug: unhashable type: 'list'

ISSUE TYPE

• Bug Report

COMPONENT NAME

Tags parameter

ANSIBLE VERSION

ansible 2.7.4
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/site-packages/ansible
  executable location = /usr/bin/ansible
  python version = 2.7.5 (default, May 31 2018, 09:41:32) [GCC 4.8.5 20150623 (Red Hat 4.8.5-28)]

CONFIGURATION

Nothing changed from defaults.

OS / ENVIRONMENT

Red Hat Enterprise Linux Server release 7.5 (Maipo)

STEPS TO REPRODUCE

Run with ansible-playbook -vvvv foo.yml.

- hosts: all
  remote_user: root
  gather_facts: no
  vars:
    foo: ['foo', 'bar']
  tasks:
  - debug:
      msg: "{{ foo }}"
    tags: "{{ foo }}"

EXPECTED RESULTS

Expect no error/exception.

ACTUAL RESULTS

ansible-playbook 2.7.4
  config file = /etc/ansible/ansible.cfg
  configured module search path = [u'/root/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python2.7/site-packages/ansible
  executable location = /usr/bin/ansible-playbook
  python version = 2.7.5 (default, May 31 2018, 09:41:32) [GCC 4.8.5 20150623 (Red Hat 4.8.5-28)]
Using /etc/ansible/ansible.cfg as config file
setting up inventory plugins
/etc/ansible/hosts did not meet host_list requirements, check plugin documentation if this is unexpected
/etc/ansible/hosts did not meet script requirements, check plugin documentation if this is unexpected
Set default localhost to localhost
Parsed /etc/ansible/hosts inventory source with ini plugin
Loading callback plugin default of type stdout, v2.0 from /usr/lib/python2.7/site-packages/ansible/plugins/callback/default.pyc

PLAYBOOK: foo.yml ***************************************************************************************************************************************************************************************************************************
1 plays in foo.yml

PLAY [all] **********************************************************************************************************************************************************************************************************************************
ERROR! Unexpected Exception, this is probably a bug: unhashable type: 'list'
the full traceback was:

Traceback (most recent call last):
  File "/usr/bin/ansible-playbook", line 118, in <module>
    exit_code = cli.run()
  File "/usr/lib/python2.7/site-packages/ansible/cli/playbook.py", line 122, in run
    results = pbex.run()
  File "/usr/lib/python2.7/site-packages/ansible/executor/playbook_executor.py", line 156, in run
    result = self._tqm.run(play=play)
  File "/usr/lib/python2.7/site-packages/ansible/executor/task_queue_manager.py", line 263, in run
    start_at_done=self._start_at_done,
  File "/usr/lib/python2.7/site-packages/ansible/executor/play_iterator.py", line 197, in __init__
    new_block = block.filter_tagged_tasks(play_context, all_vars)
  File "/usr/lib/python2.7/site-packages/ansible/playbook/block.py", line 394, in filter_tagged_tasks
    return evaluate_block(self)
  File "/usr/lib/python2.7/site-packages/ansible/playbook/block.py", line 389, in evaluate_block
    new_block.block = evaluate_and_append_task(block.block)
  File "/usr/lib/python2.7/site-packages/ansible/playbook/block.py", line 383, in evaluate_and_append_task
    task.evaluate_tags(play_context.only_tags, play_context.skip_tags, all_vars=all_vars)):
  File "/usr/lib/python2.7/site-packages/ansible/playbook/taggable.py", line 63, in evaluate_tags
    tags = set([i for i, _ in itertools.groupby(tags)])
TypeError: unhashable type: 'list'

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