config: T0000: fix mutable default argument in config API methods

[andamasov]

Summary

• Fix mutable default argument (default=[]) in four Config class methods: return_values, list_nodes, return_effective_values, and list_effective_nodes
• Changed each default=[] parameter to default=None with an explicit if default is None: default = [] guard inside the function body
• This prevents the classic Python bug where a mutable default argument is shared across all calls, which can lead to silent state corruption

Test plan

• Verify that callers passing no default argument still receive an empty list as before
• Verify that callers passing an explicit default value still receive that value when the node is missing
• Run existing unit/integration tests to confirm no regressions

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[Copilot]

Pull request overview

This PR updates the vyos.config.Config API to avoid using mutable list literals as default argument values in four list-returning helper methods.

Changes:

• Changed default=[] to default=None for return_values(), list_nodes(), return_effective_values(), and list_effective_nodes().
• Added an if default is None: default = [] guard in each method to preserve previous behavior while preventing mutable-default pitfalls.

Comments suppressed due to low confidence (1)

python/vyos/config.py:493

• The default parameter is part of the public signature here, but it isn't documented in the docstring Args section, and the Returns section implies [] is always returned when missing. Please document default (and that it's returned when the node is missing/empty) so callers understand the behavior.

    def return_values(self, path, default=None):
        """
        Retrieve all values of a multi-value leaf node in the running or proposed config

        Args:
            path (str): Configuration tree path

        Returns:
            str list: Node values, if it has any
            []: if node does not exist

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[Copilot]

default is part of the signature but isn't documented. Please add it to the docstring and clarify that the method returns default.copy() when no nodes are found.

[Copilot]

The PR description says mutable defaults were fixed for the Config API methods listed, but this file still contains mutable default arguments (e.g., get_config_dict(self, path=...) and get_config_defaults(self, path=...) use path=[]). Either include those in this change set or adjust the PR description/scope so it’s not misleading.

[Copilot]

default is accepted by this method but not described in the docstring. Please add it to Args and clarify what is returned when the path doesn't exist (currently default.copy() when no nodes are found).

[Copilot]

This docstring doesn't mention the default parameter even though it's part of the signature, and it doesn't explain the fallback behavior when the node is missing/empty. Please document default and the exact return semantics.

[github-actions]

CI integration ❌ failed!

Details

CI logs

• CLI Smoketests 👍 passed
• CLI Smoketests (interfaces only) 👍 passed
• Config tests ❌ failed
• RAID1 tests 👍 passed
• CLI Smoketests VPP 👍 passed
• Config tests VPP 👍 passed
• TPM tests 👍 passed