will be raised otherwise.

.. versionchanged:: 8.2.0
    Introduction of ``deprecated``.

.. versionchanged:: 8.2
    Adding duplicate parameter names to a :class:`~click.core.Command` will
    result in a ``UserWarning`` being shown.

.. versionchanged:: 8.2
    Adding duplicate parameter names to a :class:`~click.core.Command` will
    result in a ``UserWarning`` being shown.

.. versionchanged:: 8.0
    ``process_value`` validates required parameters and bounded
    ``nargs``, and invokes the parameter callback before returning
    the value. This allows the callback to validate prompts.
    ``full_process_value`` is removed.

.. versionchanged:: 8.0
    ``autocompletion`` is renamed to ``shell_complete`` and has new
    semantics described above. The old name is deprecated and will
    be removed in 8.1, until then it will be wrapped to match the
    new requirements.

.. versionchanged:: 8.0
    For ``multiple=True, nargs>1``, the default must be a list of
    tuples.

.. versionchanged:: 8.0
    Setting a default is no longer required for ``nargs>1``, it will
    default to ``None``. ``multiple=True`` or ``nargs=-1`` will
    default to ``()``.

.. versionchanged:: 7.1
    Empty environment variables are ignored rather than taking the
    empty string value. This makes it possible for scripts to clear
    variables if they can't unset them.

.. versionchanged:: 2.0
    Changed signature for parameter callback to also be passed the
    parameter. The old callback format will still work, but it will
    raise a warning to give you a chance to migrate the code easier.
Ú	parameterNc