Return None in case of invalid syntax

[vivekraj2000]

Type of Change

• Bug fix
• New feature
• Breaking change
• Documentation update

Description

Summary:
The device_credential_playbook_config_generator module creates YAML files even when the filters match nothing. This contradicts the documented behavior, which says no file should be created and the module should return a "No configurations found" message.

Made changes to return None in case of invalid filters

Testing Done:

• [] Manual testing
• [] Unit tests
• [] Integration tests

Test cases covered: [Mention test case IDs or brief points]

Checklist

• My code follows the style guidelines of this project
• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules
• All the sanity checks have been completed and the sanity test cases have been executed

Ansible Best Practices

• Tasks are idempotent (can be run multiple times without changing state)
• Variables and secrets are handled securely (e.g., using ansible-vault or environment variables)
• Playbooks are modular and reusable
• Handlers are used for actions that need to run on change

Documentation

• All options and parameters are documented clearly.
• Examples are provided and tested.
• Notes and limitations are clearly stated.

Screenshots (if applicable)

Notes to Reviewers

[madhansansel]

Add a new line after this.