touch a file in dry-run gives an error in ansible-2.6.0

[dnmvisser]

SUMMARY

Trying to use the file module's touch state in dry-run mode gives UnboundLocalError: local variable 'diff' referenced before assignment in 2.6.0.
In 2.5.5 this worked OK.

ISSUE TYPE

• Bug Report

COMPONENT NAME

file

ANSIBLE VERSION

ansible 2.6.0
  config file = /Users/someuser/ansible/ansible.cfg
  configured module search path = [u'/Users/someuser/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/someuser/.virtualenvs/ansible-2.6.0/lib/python2.7/site-packages/ansible
  executable location = /Users/someuser/.virtualenvs/ansible-2.6.0/bin/ansible
  python version = 2.7.15 (default, May  1 2018, 16:44:08) [GCC 4.2.1 Compatible Apple LLVM 9.1.0 (clang-902.0.39.1)]

CONFIGURATION

ALLOW_WORLD_READABLE_TMPFILES(/Users/username/ansible/ansible.cfg) = True
ANSIBLE_PIPELINING(/Users/username/ansible/ansible.cfg) = True
ANSIBLE_SSH_CONTROL_PATH(/Users/username/ansible/ansible.cfg) = ~/.ssh/cm/%%C
CACHE_PLUGIN(/Users/username/ansible/ansible.cfg) = jsonfile
CACHE_PLUGIN_CONNECTION(/Users/username/ansible/ansible.cfg) = ~/.ansible/cached_facts
CACHE_PLUGIN_TIMEOUT(/Users/username/ansible/ansible.cfg) = 600
DEFAULT_FILTER_PLUGIN_PATH(/Users/username/ansible/ansible.cfg) = [u'/Users/username/ansible/filters']
DEFAULT_FORKS(/Users/username/ansible/ansible.cfg) = 25
DEFAULT_GATHERING(/Users/username/ansible/ansible.cfg) = smart
DEFAULT_HOST_LIST(/Users/username/ansible/ansible.cfg) = [u'/Users/username/ansible/inventory.yml']
DEFAULT_JINJA2_EXTENSIONS(/Users/username/ansible/ansible.cfg) = jinja2.ext.loopcontrols
DEFAULT_NO_TARGET_SYSLOG(/Users/username/ansible/ansible.cfg) = True
DEFAULT_ROLES_PATH(/Users/username/ansible/ansible.cfg) = [u'/Users/username/ansible/roles']
DEFAULT_TIMEOUT(/Users/username/ansible/ansible.cfg) = 20
DEFAULT_TRANSPORT(/Users/username/ansible/ansible.cfg) = ssh
DEFAULT_VAULT_PASSWORD_FILE(/Users/username/ansible/ansible.cfg) = /Users/username/ansible/files/open_vault.sh
RETRY_FILES_ENABLED(/Users/username/ansible/ansible.cfg) = False

OS / ENVIRONMENT

N/A

STEPS TO REPRODUCE

---
- name: Test playbook
  hosts: some.host.name

  tasks:
    - name: Touch some file
      file:
        dest: /tmp/test
        state: touch

EXPECTED RESULTS

(ansible-2.5.5) username@geant-ams-049:~/ansible$ ansible-playbook playbooks/test1.yml -CD -vvv
ansible-playbook 2.5.5
  config file = /Users/username/ansible/ansible.cfg
  configured module search path = [u'/Users/username/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/username/.virtualenvs/ansible-2.5.5/lib/python2.7/site-packages/ansible
  executable location = /Users/username/.virtualenvs/ansible-2.5.5/bin/ansible-playbook
  python version = 2.7.15 (default, May  1 2018, 16:44:08) [GCC 4.2.1 Compatible Apple LLVM 9.1.0 (clang-902.0.39.1)]
Using /Users/username/ansible/ansible.cfg as config file
Parsed /Users/username/ansible/inventory.yml inventory source with ini plugin

PLAYBOOK: test1.yml **************************************************************************************************************************************
1 plays in playbooks/test1.yml

PLAY [Test playbook] *************************************************************************************************************************************
META: ran handlers

TASK [Touch some file] ***********************************************************************************************************************************
task path: /Users/username/ansible/playbooks/test1.yml:6
Using module file /Users/username/.virtualenvs/ansible-2.5.5/lib/python2.7/site-packages/ansible/modules/files/file.py
<some.host.name> ESTABLISH SSH CONNECTION FOR USER: None
<some.host.name> SSH: EXEC ssh -C -o ControlMaster=auto -o ControlPersist=60s -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=20 -o 'ControlPath=~/.ssh/cm/%C' some.host.name '/bin/sh -c '"'"'/usr/bin/python && sleep 0'"'"''
<some.host.name> (0, '\n{"group": "localadm", "uid": 1002, "dest": "/tmp/test", "changed": true, "owner": "visser", "state": "file", "gid": 1002, "mode": "0644", "invocation": {"module_args": {"directory_mode": null, "force": false, "remote_src": null, "path": "/tmp/test", "owner": null, "follow": true, "group": null, "unsafe_writes": null, "state": "touch", "content": null, "serole": null, "diff_peek": null, "setype": null, "dest": "/tmp/test", "selevel": null, "original_basename": null, "regexp": null, "validate": null, "src": null, "seuser": null, "recurse": false, "delimiter": null, "mode": null, "attributes": null, "backup": null}}, "diff": {"after": {"path": "/tmp/test", "state": "touch"}, "before": {"path": "/tmp/test", "state": "file"}}, "size": 0}\n', '')
--- before
+++ after
@@ -1,4 +1,4 @@
 {
     "path": "/tmp/test",
-    "state": "file"
+    "state": "touch"
 }

changed: [some.host.name] => {
    "changed": true, 
    "dest": "/tmp/test", 
    "diff": {
        "after": {
            "path": "/tmp/test", 
            "state": "touch"
        }, 
        "before": {
            "path": "/tmp/test", 
            "state": "file"
        }
    }, 
    "gid": 1002, 
    "group": "localadm", 
    "invocation": {
        "module_args": {
            "attributes": null, 
            "backup": null, 
            "content": null, 
            "delimiter": null, 
            "dest": "/tmp/test", 
            "diff_peek": null, 
            "directory_mode": null, 
            "follow": true, 
            "force": false, 
            "group": null, 
            "mode": null, 
            "original_basename": null, 
            "owner": null, 
            "path": "/tmp/test", 
            "recurse": false, 
            "regexp": null, 
            "remote_src": null, 
            "selevel": null, 
            "serole": null, 
            "setype": null, 
            "seuser": null, 
            "src": null, 
            "state": "touch", 
            "unsafe_writes": null, 
            "validate": null
        }
    }, 
    "mode": "0644", 
    "owner": "visser", 
    "size": 0, 
    "state": "file", 
    "uid": 1002
}
META: ran handlers
META: ran handlers

PLAY RECAP ***********************************************************************************************************************************************
some.host.name           : ok=1    changed=1    unreachable=0    failed=0   

ACTUAL RESULTS

(ansible-2.6.0) username@geant-ams-049:~/ansible$ ansible-playbook playbooks/test1.yml -CD -vvv
ansible-playbook 2.6.0
  config file = /Users/username/ansible/ansible.cfg
  configured module search path = [u'/Users/username/.ansible/plugins/modules', u'/usr/share/ansible/plugins/modules']
  ansible python module location = /Users/username/.virtualenvs/ansible-2.6.0/lib/python2.7/site-packages/ansible
  executable location = /Users/username/.virtualenvs/ansible-2.6.0/bin/ansible-playbook
  python version = 2.7.15 (default, May  1 2018, 16:44:08) [GCC 4.2.1 Compatible Apple LLVM 9.1.0 (clang-902.0.39.1)]
Using /Users/username/ansible/ansible.cfg as config file
Parsed /Users/username/ansible/inventory.yml inventory source with ini plugin

PLAYBOOK: test1.yml **************************************************************************************************************************************
1 plays in playbooks/test1.yml

PLAY [Test playbook] *************************************************************************************************************************************
META: ran handlers

TASK [Touch some file] ***********************************************************************************************************************************
task path: /Users/username/ansible/playbooks/test1.yml:6
Using module file /Users/username/.virtualenvs/ansible-2.6.0/lib/python2.7/site-packages/ansible/modules/files/file.py
<some.host.name> ESTABLISH SSH CONNECTION FOR USER: None
<some.host.name> SSH: EXEC ssh -C -o ControlMaster=auto -o ControlPersist=60s -o KbdInteractiveAuthentication=no -o PreferredAuthentications=gssapi-with-mic,gssapi-keyex,hostbased,publickey -o PasswordAuthentication=no -o ConnectTimeout=20 -o 'ControlPath=~/.ssh/cm/%C' some.host.name '/bin/sh -c '"'"'/usr/bin/python && sleep 0'"'"''
<some.host.name> (1, '', 'Traceback (most recent call last):\n  File "/tmp/ansible_eWqv0v/ansible_module_file.py", line 739, in <module>\n    main()\n  File "/tmp/ansible_eWqv0v/ansible_module_file.py", line 731, in main\n    result = execute_touch(path, follow)\n  File "/tmp/ansible_eWqv0v/ansible_module_file.py", line 373, in execute_touch\n    return {\'dest\': path, \'changed\': True, \'diff\': diff}\nUnboundLocalError: local variable \'diff\' referenced before assignment\n')
The full traceback is:
Traceback (most recent call last):
  File "/tmp/ansible_eWqv0v/ansible_module_file.py", line 739, in <module>
    main()
  File "/tmp/ansible_eWqv0v/ansible_module_file.py", line 731, in main
    result = execute_touch(path, follow)
  File "/tmp/ansible_eWqv0v/ansible_module_file.py", line 373, in execute_touch
    return {'dest': path, 'changed': True, 'diff': diff}
UnboundLocalError: local variable 'diff' referenced before assignment

fatal: [some.host.name]: FAILED! => { 
    "changed": false,
    "module_stderr": "Traceback (most recent call last):\n  File \"/tmp/ansible_eWqv0v/ansible_module_file.py\", line 739, in <module>\n    main()\n  File \"/tmp/ansible_eWqv0v/ansible_module_file.py\", line 731, in main\n    result = execute_touch(path, follow)\n  File \"/tmp/ansible_eWqv0v/ansible_module_file.py\", line 373, in execute_touch\n    return {'dest': path, 'changed': True, 'diff': diff}\nUnboundLocalError: local variable 'diff' referenced before assignment\n", 
    "module_stdout": "",
    "msg": "MODULE FAILURE", 
    "rc": 1
}

PLAY RECAP ***********************************************************************************************************************************************
some.host.name           : ok=0    changed=0    unreachable=0    failed=1  

[ansibot]

Files identified in the description:

• lib/ansible/modules/files/file.py

If these files are inaccurate, please update the component name section of the description or use the !component bot command.

click here for bot help

[s-hertel]

This was fixed in devel in 22a6927 and will be backported to 2.6.1 in #42129.