Unquoted variables turns into `!!null`

[konstruktoid]

Summary

If a variable is unquoted, {{ a_message }}, the result will be { { a_message: !!null "" }: !!null "" } after running ansible-lint.

Issue Type

• Bug Report

OS / ENVIRONMENT

ansible-lint 25.9.1.dev1 using ansible-core:2.20.0.dev0 ansible-compat:25.8.1 ruamel-yaml:0.18.15 ruamel-yaml-clib:0.2.12

uv pip install -U -r https://raw.githubusercontent.com/konstruktoid/ansible-role-hardening/refs/heads/master/requirements-upstream.txt

STEPS TO REPRODUCE

---
- name: Test Playbook
  hosts: localhost
  gather_facts: true
  vars:
    a_message: "At the gates"
  tasks:
    - name: Print a message
      debug:
        msg: {{ a_message }}

$ ansible-lint --fix ./test.yml
[WARNING]: Deprecation warnings can be disabled by setting `deprecation_warnings=False` in ansible.cfg.
[DEPRECATION WARNING]: Importing 'to_bytes' from 'ansible.module_utils._text' is deprecated. This feature will be removed from ansible-core version 2.24. Use ansible.module_utils.common.text.converters instead.
WARNING  Project directory /.ansible cannot be used for caching as it is not writable.
WARNING  Listing 1 violation(s) that are fatal

Modified 1 file.
# Rule Violation Summary

  1 load-failure profile:min tags:core,unskippable

Failed: 1 failure(s), 0 warning(s) in 1 files processed of 1 encountered.
load-failure[runtimeerror]: ('Failed to load YAML file', PosixPath('test.yml')) (warning)
test.yml:1 while constructing a mapping
  in "<unicode string>", line 10, column 14
found unhashable key
  in "<unicode string>", line 10, column 15

---
- name: Test Playbook
  hosts: localhost
  gather_facts: true
  vars:
    a_message: "At the gates"
  tasks:
    - name: Print a message
      debug:
        msg: { { a_message: !!null "" }: !!null "" }

Desired Behavior

Quoted variable as in earlier versions.

Actual Behavior

See above.