omit does not work properly with become

[mohd-akram]

Summary

omit does not seem to work properly with become.

Issue Type

Bug Report

Component Name

become

Ansible Version

$ ansible --version
ansible 2.9.25
  config file = /etc/ansible/ansible.cfg
  configured module search path = ['/home/mohamed/.ansible/plugins/modules', '/usr/share/ansible/plugins/modules']
  ansible python module location = /usr/lib/python3.9/site-packages/ansible
  executable location = /usr/bin/ansible
  python version = 3.9.7 (default, Aug 30 2021, 00:00:00) [GCC 11.2.1 20210728 (Red Hat 11.2.1-1)]

Configuration

$ ansible-config dump --only-changed

OS / Environment

Fedora 34

Steps to Reproduce

- hosts: localhost
  become: yes
  tasks:
    - shell: echo $USER
    - shell: echo $USER
      become: '{{ omit }}'

ansible-playbook --ask-become-pass --verbose become-omit.yml

Expected Results

USER=root in both cases

Actual Results

Using /etc/ansible/ansible.cfg as config file
BECOME password: 
[WARNING]: provided hosts list is empty, only localhost is available. Note that the implicit localhost does not match 'all'

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

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

TASK [shell] *****************************************************************************************************************************************
changed: [localhost] => {"changed": true, "cmd": "echo $USER", "delta": "0:00:00.006134", "end": "2021-09-13 14:43:44.075108", "rc": 0, "start": "2021-09-13 14:43:44.068974", "stderr": "", "stderr_lines": [], "stdout": "root", "stdout_lines": ["root"]}

TASK [shell] *****************************************************************************************************************************************
changed: [localhost] => {"changed": true, "cmd": "echo $USER", "delta": "0:00:00.005727", "end": "2021-09-13 14:43:44.411115", "rc": 0, "start": "2021-09-13 14:43:44.405388", "stderr": "", "stderr_lines": [], "stdout": "mohamed", "stdout_lines": ["mohamed"]}

PLAY RECAP *******************************************************************************************************************************************
localhost                  : ok=3    changed=2    unreachable=0    failed=0    skipped=0    rescued=0    ignored=0

Code of Conduct

• I agree to follow the Ansible Code of Conduct

[ansibot]

Files identified in the description:

• lib/ansible/playbook/become.py

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

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[mkrizek]

I am not sure if this is something that we want to address yet but potential POC fix might be:

diff --git a/lib/ansible/playbook/base.py b/lib/ansible/playbook/base.py
index 564ce0cd3a5..4842b8ce91b 100644
--- a/lib/ansible/playbook/base.py
+++ b/lib/ansible/playbook/base.py
@@ -652,6 +652,13 @@ class FieldAttributeBase(with_metaclass(BaseMeta, object)):
                 # if this evaluated to the omit value, set the value back to
                 # the default specified in the FieldAttribute and move on
                 if omit_value is not None and value == omit_value:
+                    if attribute.inherit:
+                        setattr(self, name, Sentinel)
+                        try:
+                            setattr(self, name, self._get_parent_attribute(name))
+                        except AttributeError:
+                            # PlayContext, the value will be set in TE via PC.set_task_and_variable_override
+                            pass
+                        continue
                     if callable(attribute.default):
                         setattr(self, name, attribute.default())
                     else:

EDIT: diff updated

[bcoca]

The bug is due to 'omit' forcing the keyword to it's default value (none/false), not it's inherited value (yes/true).
https://github.com/ansible/ansible/blob/devel/lib/ansible/playbook/base.py#L530