#143 gdtest_docstring_warnings

"""Package with Warnings sections in docstrings."""

__version__ = "0.1.0"
__all__ = ["unsafe_eval", "mutable_default"]


def unsafe_eval(expr: str) -> object:
    """
    Evaluate a Python expression string and return the result.

    Parses and evaluates the given expression string using
    Python's built-in ``eval()`` function.

    Parameters
    ----------
    expr
        A string containing a valid Python expression.

    Returns
    -------
    object
        The result of evaluating the expression.

    Raises
    ------
    SyntaxError
        If the expression string is not valid Python.
    NameError
        If the expression references undefined names.

    Warnings
    --------
    Never use with untrusted input. This function uses ``eval()``
    internally and can execute arbitrary Python code. An attacker
    could craft an expression that deletes files, exfiltrates
    data, or compromises the system.

    Examples
    --------
    >>> unsafe_eval("2 + 3")
    5

    >>> unsafe_eval("[i**2 for i in range(5)]")
    [0, 1, 4, 9, 16]
    """
    return eval(expr)


def mutable_default(items: list = None) -> list:
    """
    Append a marker value to a list and return it.

    If no list is provided, an internal default list is used.
    Appends the string ``"added"`` to the list and returns it.

    Parameters
    ----------
    items
        A list to append to. If ``None``, a new empty list
        is created for each call.

    Returns
    -------
    list
        The list with ``"added"`` appended.

    Warnings
    --------
    If you modify this function to use a mutable default argument
    (e.g., ``items=[]``), the default empty list would be shared
    across all calls that omit the argument. Each call would
    mutate the same list object, leading to surprising
    accumulation of values.

    Always use ``None`` as the default and create a new list
    inside the function body to avoid this pitfall.

    Examples
    --------
    >>> mutable_default()
    ['added']

    >>> mutable_default(["existing"])
    ['existing', 'added']
    """
    if items is None:
        items = []
    items.append("added")
    return items