Ansible tries to parse contents of diffs

[duijf]

I've tried to search for this problem in the issue tracker with the keywords --diff, crash, and parse, but haven't found anything.

SUMMARY

Diff printing seems to attempt to resolve variables in diffed files/parse them.

ISSUE TYPE

• Bug Report

COMPONENT NAME

Diff mode and copy module.

ANSIBLE VERSION

ansible 2.6.2                                                                                          
  config file = /home/laurens/repos/channable/devops/ansible/ansible.cfg
  configured module search path = ['/home/laurens/repos/channable/devops/ansible/modules']
  ansible python module location = /home/laurens/env/devops/lib/python3.6/site-packages/ansible
  executable location = /home/laurens/env/devops/bin/ansible
  python version = 3.6.5 (default, Apr  1 2018, 05:46:30) [GCC 7.3.0]

and

ansible 2.8.0.dev0
  config file = None
  configured module search path = ['/home/laurens/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /home/laurens/env/devops/lib/python3.6/site-packages/ansible
  executable location = /home/laurens/env/devops/bin/ansible
  python version = 3.6.5 (default, Apr  1 2018, 05:46:30) [GCC 7.3.0]

CONFIGURATION

No output. Running with default config.

OS / ENVIRONMENT

Originally seen in a more complex setting, but reproducible when running on Ubuntu 18.04, deploying with ansible_connection=local.

STEPS TO REPRODUCE

I've created a git repository which has a minimal test case: https://github.com/duijf/ansible-bug-report

Please tell me if anything is unclear.

EXPECTED RESULTS

Ansible does not crash and reports changed results correctly.

ACTUAL RESULTS

Ansible crashes.

~/repos/channable/ansible-bug-report master
devops ❯ ansible-playbook -i inventory playbook.yml --diff

PLAY [localhost] ***************************************************************************************

TASK [Gathering Facts] *********************************************************************************
ok: [localhost]

TASK [problem : copy problematic file] *****************************************************************
--- before
+++ after: /home/laurens/repos/channable/ansible-bug-report/roles/problem/files/problem.yml
@@ -0,0 +1,7 @@
+The problem was originally found when copying prometheus
+templates, which can contain things like {{ $labels.instance }}.
+
+If this were a file in the `templates/` directory, I'd agree
+that this is asking for problems. However, this only gives
+problems when registering things to a variable and acting on
+it.                                                                                                    
                                                                                                        
changed: [localhost]                                                                                    
                                                                                                        
TASK [problem : inspect results] ***********************************************************************
fatal: [localhost]: FAILED! => {"msg": "An unhandled exception occurred while templating '{'diff': [{'before': '', 'after_header': '/home/laurens/repos/channable/ansible-bug-report/roles/problem/files/problem.yml', 'after': \"The problem was originally found when copying prometheus\\ntemplates, which can contain things like {{ $labels.instance }}.\\n\\nIf this were a file in the `templates/` directory, I'd agree\\nthat this is asking for problems. However, this only gives\\nproblems when registering things to a variable and acting on\\nit.\\n\"}], 'src': '/home/laurens/.ansible/tmp/ansible-tmp-1537170980.7106235-254323551122550/source', 'changed': True, 'group': 'laurens', 'uid': 1000, 'dest': '/tmp/problem.yml', 'checksum': '42a9a3edeb77bac53775ea092fab3cad962c0872', 'md5sum': '6e6ce6086486a66f1cdab91b98d0b7f0', 'owner': 'laurens', 'state': 'file', 'gid': 1000, 'mode': '0664', 'size': 308, 'failed': False}'. Error was a <class 'ansible.errors.AnsibleError'>, original message: template error while templating string: unexpected char '$' at 101. String: The problem was originally found when copying prometheus\ntemplates, which can contain things like {{ $labels.instance }}.\n\nIf this were a file in the `templates/` directory, I'd agree\nthat this is asking for problems. However, this only gives\nproblems when registering things to a variable and acting on\nit.\n"}                                                                       
        to retry, use: --limit @/home/laurens/repos/channable/ansible-bug-report/playbook.retry         
                                                                                                        
PLAY RECAP *********************************************************************************************
localhost                  : ok=2    changed=1    unreachable=0    failed=1   

This only happens when:

• --diff is used.
• The file is changed, so the diff contains the variables.

It seems like Ansible is trying to interpret the output of the diff, since it prints unexpected char '$' at 101.

[duijf]

For anyone reading this from Google searches. You can work around this problem on a per-task basis by setting:

- name: mytask
  copy:
    src: whatevs
    dest: whatevs
  diff: no

[sivel]

We've tracked this down to a python3 compatibility issue, and are discussing the correct fix.