venv

1 files changed, 3042 insertions, 0 deletions

diff --git a/venv/lib/python3.11/site-packages/click/core.py b/venv/lib/python3.11/site-packages/click/core.py
new file mode 100644
index 0000000..cc65e89
--- /dev/null
+++ b/venv/lib/python3.11/site-packages/click/core.py
@@ -0,0 +1,3042 @@
+import enum
+import errno
+import inspect
+import os
+import sys
+import typing as t
+from collections import abc
+from contextlib import contextmanager
+from contextlib import ExitStack
+from functools import update_wrapper
+from gettext import gettext as _
+from gettext import ngettext
+from itertools import repeat
+from types import TracebackType
+
+from . import types
+from .exceptions import Abort
+from .exceptions import BadParameter
+from .exceptions import ClickException
+from .exceptions import Exit
+from .exceptions import MissingParameter
+from .exceptions import UsageError
+from .formatting import HelpFormatter
+from .formatting import join_options
+from .globals import pop_context
+from .globals import push_context
+from .parser import _flag_needs_value
+from .parser import OptionParser
+from .parser import split_opt
+from .termui import confirm
+from .termui import prompt
+from .termui import style
+from .utils import _detect_program_name
+from .utils import _expand_args
+from .utils import echo
+from .utils import make_default_short_help
+from .utils import make_str
+from .utils import PacifyFlushWrapper
+
+if t.TYPE_CHECKING:
+    import typing_extensions as te
+    from .shell_completion import CompletionItem
+
+F = t.TypeVar("F", bound=t.Callable[..., t.Any])
+V = t.TypeVar("V")
+
+
+def _complete_visible_commands(
+    ctx: "Context", incomplete: str
+) -> t.Iterator[t.Tuple[str, "Command"]]:
+    """List all the subcommands of a group that start with the
+    incomplete value and aren't hidden.
+
+    :param ctx: Invocation context for the group.
+    :param incomplete: Value being completed. May be empty.
+    """
+    multi = t.cast(MultiCommand, ctx.command)
+
+    for name in multi.list_commands(ctx):
+        if name.startswith(incomplete):
+            command = multi.get_command(ctx, name)
+
+            if command is not None and not command.hidden:
+                yield name, command
+
+
+def _check_multicommand(
+    base_command: "MultiCommand", cmd_name: str, cmd: "Command", register: bool = False
+) -> None:
+    if not base_command.chain or not isinstance(cmd, MultiCommand):
+        return
+    if register:
+        hint = (
+            "It is not possible to add multi commands as children to"
+            " another multi command that is in chain mode."
+        )
+    else:
+        hint = (
+            "Found a multi command as subcommand to a multi command"
+            " that is in chain mode. This is not supported."
+        )
+    raise RuntimeError(
+        f"{hint}. Command {base_command.name!r} is set to chain and"
+        f" {cmd_name!r} was added as a subcommand but it in itself is a"
+        f" multi command. ({cmd_name!r} is a {type(cmd).__name__}"
+        f" within a chained {type(base_command).__name__} named"
+        f" {base_command.name!r})."
+    )
+
+
+def batch(iterable: t.Iterable[V], batch_size: int) -> t.List[t.Tuple[V, ...]]:
+    return list(zip(*repeat(iter(iterable), batch_size)))
+
+
+@contextmanager
+def augment_usage_errors(
+    ctx: "Context", param: t.Optional["Parameter"] = None
+) -> t.Iterator[None]:
+    """Context manager that attaches extra information to exceptions."""
+    try:
+        yield
+    except BadParameter as e:
+        if e.ctx is None:
+            e.ctx = ctx
+        if param is not None and e.param is None:
+            e.param = param
+        raise
+    except UsageError as e:
+        if e.ctx is None:
+            e.ctx = ctx
+        raise
+
+
+def iter_params_for_processing(
+    invocation_order: t.Sequence["Parameter"],
+    declaration_order: t.Sequence["Parameter"],
+) -> t.List["Parameter"]:
+    """Given a sequence of parameters in the order as should be considered
+    for processing and an iterable of parameters that exist, this returns
+    a list in the correct order as they should be processed.
+    """
+
+    def sort_key(item: "Parameter") -> t.Tuple[bool, float]:
+        try:
+            idx: float = invocation_order.index(item)
+        except ValueError:
+            idx = float("inf")
+
+        return not item.is_eager, idx
+
+    return sorted(declaration_order, key=sort_key)
+
+
+class ParameterSource(enum.Enum):
+    """This is an :class:`~enum.Enum` that indicates the source of a
+    parameter's value.
+
+    Use :meth:`click.Context.get_parameter_source` to get the
+    source for a parameter by name.
+
+    .. versionchanged:: 8.0
+        Use :class:`~enum.Enum` and drop the ``validate`` method.
+
+    .. versionchanged:: 8.0
+        Added the ``PROMPT`` value.
+    """
+
+    COMMANDLINE = enum.auto()
+    """The value was provided by the command line args."""
+    ENVIRONMENT = enum.auto()
+    """The value was provided with an environment variable."""
+    DEFAULT = enum.auto()
+    """Used the default specified by the parameter."""
+    DEFAULT_MAP = enum.auto()
+    """Used a default provided by :attr:`Context.default_map`."""
+    PROMPT = enum.auto()
+    """Used a prompt to confirm a default or provide a value."""
+
+
+class Context:
+    """The context is a special internal object that holds state relevant
+    for the script execution at every single level.  It's normally invisible
+    to commands unless they opt-in to getting access to it.
+
+    The context is useful as it can pass internal objects around and can
+    control special execution features such as reading data from
+    environment variables.
+
+    A context can be used as context manager in which case it will call
+    :meth:`close` on teardown.
+
+    :param command: the command class for this context.
+    :param parent: the parent context.
+    :param info_name: the info name for this invocation.  Generally this
+                      is the most descriptive name for the script or
+                      command.  For the toplevel script it is usually
+                      the name of the script, for commands below it it's
+                      the name of the script.
+    :param obj: an arbitrary object of user data.
+    :param auto_envvar_prefix: the prefix to use for automatic environment
+                               variables.  If this is `None` then reading
+                               from environment variables is disabled.  This
+                               does not affect manually set environment
+                               variables which are always read.
+    :param default_map: a dictionary (like object) with default values
+                        for parameters.
+    :param terminal_width: the width of the terminal.  The default is
+                           inherit from parent context.  If no context
+                           defines the terminal width then auto
+                           detection will be applied.
+    :param max_content_width: the maximum width for content rendered by
+                              Click (this currently only affects help
+                              pages).  This defaults to 80 characters if
+                              not overridden.  In other words: even if the
+                              terminal is larger than that, Click will not
+                              format things wider than 80 characters by
+                              default.  In addition to that, formatters might
+                              add some safety mapping on the right.
+    :param resilient_parsing: if this flag is enabled then Click will
+                              parse without any interactivity or callback
+                              invocation.  Default values will also be
+                              ignored.  This is useful for implementing
+                              things such as completion support.
+    :param allow_extra_args: if this is set to `True` then extra arguments
+                             at the end will not raise an error and will be
+                             kept on the context.  The default is to inherit
+                             from the command.
+    :param allow_interspersed_args: if this is set to `False` then options
+                                    and arguments cannot be mixed.  The
+                                    default is to inherit from the command.
+    :param ignore_unknown_options: instructs click to ignore options it does
+                                   not know and keeps them for later
+                                   processing.
+    :param help_option_names: optionally a list of strings that define how
+                              the default help parameter is named.  The
+                              default is ``['--help']``.
+    :param token_normalize_func: an optional function that is used to
+                                 normalize tokens (options, choices,
+                                 etc.).  This for instance can be used to
+                                 implement case insensitive behavior.
+    :param color: controls if the terminal supports ANSI colors or not.  The
+                  default is autodetection.  This is only needed if ANSI
+                  codes are used in texts that Click prints which is by
+                  default not the case.  This for instance would affect
+                  help output.
+    :param show_default: Show the default value for commands. If this
+        value is not set, it defaults to the value from the parent
+        context. ``Command.show_default`` overrides this default for the
+        specific command.
+
+    .. versionchanged:: 8.1
+        The ``show_default`` parameter is overridden by
+        ``Command.show_default``, instead of the other way around.
+
+    .. versionchanged:: 8.0
+        The ``show_default`` parameter defaults to the value from the
+        parent context.
+
+    .. versionchanged:: 7.1
+       Added the ``show_default`` parameter.
+
+    .. versionchanged:: 4.0
+        Added the ``color``, ``ignore_unknown_options``, and
+        ``max_content_width`` parameters.
+
+    .. versionchanged:: 3.0
+        Added the ``allow_extra_args`` and ``allow_interspersed_args``
+        parameters.
+
+    .. versionchanged:: 2.0
+        Added the ``resilient_parsing``, ``help_option_names``, and
+        ``token_normalize_func`` parameters.
+    """
+
+    #: The formatter class to create with :meth:`make_formatter`.
+    #:
+    #: .. versionadded:: 8.0
+    formatter_class: t.Type["HelpFormatter"] = HelpFormatter
+
+    def __init__(
+        self,
+        command: "Command",
+        parent: t.Optional["Context"] = None,
+        info_name: t.Optional[str] = None,
+        obj: t.Optional[t.Any] = None,
+        auto_envvar_prefix: t.Optional[str] = None,
+        default_map: t.Optional[t.MutableMapping[str, t.Any]] = None,
+        terminal_width: t.Optional[int] = None,
+        max_content_width: t.Optional[int] = None,
+        resilient_parsing: bool = False,
+        allow_extra_args: t.Optional[bool] = None,
+        allow_interspersed_args: t.Optional[bool] = None,
+        ignore_unknown_options: t.Optional[bool] = None,
+        help_option_names: t.Optional[t.List[str]] = None,
+        token_normalize_func: t.Optional[t.Callable[[str], str]] = None,
+        color: t.Optional[bool] = None,
+        show_default: t.Optional[bool] = None,
+    ) -> None:
+        #: the parent context or `None` if none exists.
+        self.parent = parent
+        #: the :class:`Command` for this context.
+        self.command = command
+        #: the descriptive information name
+        self.info_name = info_name
+        #: Map of parameter names to their parsed values. Parameters
+        #: with ``expose_value=False`` are not stored.
+        self.params: t.Dict[str, t.Any] = {}
+        #: the leftover arguments.
+        self.args: t.List[str] = []
+        #: protected arguments.  These are arguments that are prepended
+        #: to `args` when certain parsing scenarios are encountered but
+        #: must be never propagated to another arguments.  This is used
+        #: to implement nested parsing.
+        self.protected_args: t.List[str] = []
+        #: the collected prefixes of the command's options.
+        self._opt_prefixes: t.Set[str] = set(parent._opt_prefixes) if parent else set()
+
+        if obj is None and parent is not None:
+            obj = parent.obj
+
+        #: the user object stored.
+        self.obj: t.Any = obj
+        self._meta: t.Dict[str, t.Any] = getattr(parent, "meta", {})
+
+        #: A dictionary (-like object) with defaults for parameters.
+        if (
+            default_map is None
+            and info_name is not None
+            and parent is not None
+            and parent.default_map is not None
+        ):
+            default_map = parent.default_map.get(info_name)
+
+        self.default_map: t.Optional[t.MutableMapping[str, t.Any]] = default_map
+
+        #: This flag indicates if a subcommand is going to be executed. A
+        #: group callback can use this information to figure out if it's
+        #: being executed directly or because the execution flow passes
+        #: onwards to a subcommand. By default it's None, but it can be
+        #: the name of the subcommand to execute.
+        #:
+        #: If chaining is enabled this will be set to ``'*'`` in case
+        #: any commands are executed.  It is however not possible to
+        #: figure out which ones.  If you require this knowledge you
+        #: should use a :func:`result_callback`.
+        self.invoked_subcommand: t.Optional[str] = None
+
+        if terminal_width is None and parent is not None:
+            terminal_width = parent.terminal_width
+
+        #: The width of the terminal (None is autodetection).
+        self.terminal_width: t.Optional[int] = terminal_width
+
+        if max_content_width is None and parent is not None:
+            max_content_width = parent.max_content_width
+
+        #: The maximum width of formatted content (None implies a sensible
+        #: default which is 80 for most things).
+        self.max_content_width: t.Optional[int] = max_content_width
+
+        if allow_extra_args is None:
+            allow_extra_args = command.allow_extra_args
+
+        #: Indicates if the context allows extra args or if it should
+        #: fail on parsing.
+        #:
+        #: .. versionadded:: 3.0
+        self.allow_extra_args = allow_extra_args
+
+        if allow_interspersed_args is None:
+            allow_interspersed_args = command.allow_interspersed_args
+
+        #: Indicates if the context allows mixing of arguments and
+        #: options or not.
+        #:
+        #: .. versionadded:: 3.0
+        self.allow_interspersed_args: bool = allow_interspersed_args
+
+        if ignore_unknown_options is None:
+            ignore_unknown_options = command.ignore_unknown_options
+
+        #: Instructs click to ignore options that a command does not
+        #: understand and will store it on the context for later
+        #: processing.  This is primarily useful for situations where you
+        #: want to call into external programs.  Generally this pattern is
+        #: strongly discouraged because it's not possibly to losslessly
+        #: forward all arguments.
+        #:
+        #: .. versionadded:: 4.0
+        self.ignore_unknown_options: bool = ignore_unknown_options
+
+        if help_option_names is None:
+            if parent is not None:
+                help_option_names = parent.help_option_names
+            else:
+                help_option_names = ["--help"]
+
+        #: The names for the help options.
+        self.help_option_names: t.List[str] = help_option_names
+
+        if token_normalize_func is None and parent is not None:
+            token_normalize_func = parent.token_normalize_func
+
+        #: An optional normalization function for tokens.  This is
+        #: options, choices, commands etc.
+        self.token_normalize_func: t.Optional[
+            t.Callable[[str], str]
+        ] = token_normalize_func
+
+        #: Indicates if resilient parsing is enabled.  In that case Click
+        #: will do its best to not cause any failures and default values
+        #: will be ignored. Useful for completion.
+        self.resilient_parsing: bool = resilient_parsing
+
+        # If there is no envvar prefix yet, but the parent has one and
+        # the command on this level has a name, we can expand the envvar
+        # prefix automatically.
+        if auto_envvar_prefix is None:
+            if (
+                parent is not None
+                and parent.auto_envvar_prefix is not None
+                and self.info_name is not None
+            ):
+                auto_envvar_prefix = (
+                    f"{parent.auto_envvar_prefix}_{self.info_name.upper()}"
+                )
+        else:
+            auto_envvar_prefix = auto_envvar_prefix.upper()
+
+        if auto_envvar_prefix is not None:
+            auto_envvar_prefix = auto_envvar_prefix.replace("-", "_")
+
+        self.auto_envvar_prefix: t.Optional[str] = auto_envvar_prefix
+
+        if color is None and parent is not None:
+            color = parent.color
+
+        #: Controls if styling output is wanted or not.
+        self.color: t.Optional[bool] = color
+
+        if show_default is None and parent is not None:
+            show_default = parent.show_default
+
+        #: Show option default values when formatting help text.
+        self.show_default: t.Optional[bool] = show_default
+
+        self._close_callbacks: t.List[t.Callable[[], t.Any]] = []
+        self._depth = 0
+        self._parameter_source: t.Dict[str, ParameterSource] = {}
+        self._exit_stack = ExitStack()
+
+    def to_info_dict(self) -> t.Dict[str, t.Any]:
+        """Gather information that could be useful for a tool generating
+        user-facing documentation. This traverses the entire CLI
+        structure.
+
+        .. code-block:: python
+
+            with Context(cli) as ctx:
+                info = ctx.to_info_dict()
+
+        .. versionadded:: 8.0
+        """
+        return {
+            "command": self.command.to_info_dict(self),
+            "info_name": self.info_name,
+            "allow_extra_args": self.allow_extra_args,
+            "allow_interspersed_args": self.allow_interspersed_args,
+            "ignore_unknown_options": self.ignore_unknown_options,
+            "auto_envvar_prefix": self.auto_envvar_prefix,
+        }
+
+    def __enter__(self) -> "Context":
+        self._depth += 1
+        push_context(self)
+        return self
+
+    def __exit__(
+        self,
+        exc_type: t.Optional[t.Type[BaseException]],
+        exc_value: t.Optional[BaseException],
+        tb: t.Optional[TracebackType],
+    ) -> None:
+        self._depth -= 1
+        if self._depth == 0:
+            self.close()
+        pop_context()
+
+    @contextmanager
+    def scope(self, cleanup: bool = True) -> t.Iterator["Context"]:
+        """This helper method can be used with the context object to promote
+        it to the current thread local (see :func:`get_current_context`).
+        The default behavior of this is to invoke the cleanup functions which
+        can be disabled by setting `cleanup` to `False`.  The cleanup
+        functions are typically used for things such as closing file handles.
+
+        If the cleanup is intended the context object can also be directly
+        used as a context manager.
+
+        Example usage::
+
+            with ctx.scope():
+                assert get_current_context() is ctx
+
+        This is equivalent::
+
+            with ctx:
+                assert get_current_context() is ctx
+
+        .. versionadded:: 5.0
+
+        :param cleanup: controls if the cleanup functions should be run or
+                        not.  The default is to run these functions.  In
+                        some situations the context only wants to be
+                        temporarily pushed in which case this can be disabled.
+                        Nested pushes automatically defer the cleanup.
+        """
+        if not cleanup:
+            self._depth += 1
+        try:
+            with self as rv:
+                yield rv
+        finally:
+            if not cleanup:
+                self._depth -= 1
+
+    @property
+    def meta(self) -> t.Dict[str, t.Any]:
+        """This is a dictionary which is shared with all the contexts
+        that are nested.  It exists so that click utilities can store some
+        state here if they need to.  It is however the responsibility of
+        that code to manage this dictionary well.
+
+        The keys are supposed to be unique dotted strings.  For instance
+        module paths are a good choice for it.  What is stored in there is
+        irrelevant for the operation of click.  However what is important is
+        that code that places data here adheres to the general semantics of
+        the system.
+
+        Example usage::
+
+            LANG_KEY = f'{__name__}.lang'
+
+            def set_language(value):
+                ctx = get_current_context()
+                ctx.meta[LANG_KEY] = value
+
+            def get_language():
+                return get_current_context().meta.get(LANG_KEY, 'en_US')
+
+        .. versionadded:: 5.0
+        """
+        return self._meta
+
+    def make_formatter(self) -> HelpFormatter:
+        """Creates the :class:`~click.HelpFormatter` for the help and
+        usage output.
+
+        To quickly customize the formatter class used without overriding
+        this method, set the :attr:`formatter_class` attribute.
+
+        .. versionchanged:: 8.0
+            Added the :attr:`formatter_class` attribute.
+        """
+        return self.formatter_class(
+            width=self.terminal_width, max_width=self.max_content_width
+        )
+
+    def with_resource(self, context_manager: t.ContextManager[V]) -> V:
+        """Register a resource as if it were used in a ``with``
+        statement. The resource will be cleaned up when the context is
+        popped.
+
+        Uses :meth:`contextlib.ExitStack.enter_context`. It calls the
+        resource's ``__enter__()`` method and returns the result. When
+        the context is popped, it closes the stack, which calls the
+        resource's ``__exit__()`` method.
+
+        To register a cleanup function for something that isn't a
+        context manager, use :meth:`call_on_close`. Or use something
+        from :mod:`contextlib` to turn it into a context manager first.
+
+        .. code-block:: python
+
+            @click.group()
+            @click.option("--name")
+            @click.pass_context
+            def cli(ctx):
+                ctx.obj = ctx.with_resource(connect_db(name))
+
+        :param context_manager: The context manager to enter.
+        :return: Whatever ``context_manager.__enter__()`` returns.
+
+        .. versionadded:: 8.0
+        """
+        return self._exit_stack.enter_context(context_manager)
+
+    def call_on_close(self, f: t.Callable[..., t.Any]) -> t.Callable[..., t.Any]:
+        """Register a function to be called when the context tears down.
+
+        This can be used to close resources opened during the script
+        execution. Resources that support Python's context manager
+        protocol which would be used in a ``with`` statement should be
+        registered with :meth:`with_resource` instead.
+
+        :param f: The function to execute on teardown.
+        """
+        return self._exit_stack.callback(f)
+
+    def close(self) -> None:
+        """Invoke all close callbacks registered with
+        :meth:`call_on_close`, and exit all context managers entered
+        with :meth:`with_resource`.
+        """
+        self._exit_stack.close()
+        # In case the context is reused, create a new exit stack.
+        self._exit_stack = ExitStack()
+
+    @property
+    def command_path(self) -> str:
+        """The computed command path.  This is used for the ``usage``
+        information on the help page.  It's automatically created by
+        combining the info names of the chain of contexts to the root.
+        """
+        rv = ""
+        if self.info_name is not None:
+            rv = self.info_name
+        if self.parent is not None:
+            parent_command_path = [self.parent.command_path]
+
+            if isinstance(self.parent.command, Command):
+                for param in self.parent.command.get_params(self):
+                    parent_command_path.extend(param.get_usage_pieces(self))
+
+            rv = f"{' '.join(parent_command_path)} {rv}"
+        return rv.lstrip()
+
+    def find_root(self) -> "Context":
+        """Finds the outermost context."""
+        node = self
+        while node.parent is not None:
+            node = node.parent
+        return node
+
+    def find_object(self, object_type: t.Type[V]) -> t.Optional[V]:
+        """Finds the closest object of a given type."""
+        node: t.Optional["Context"] = self
+
+        while node is not None:
+            if isinstance(node.obj, object_type):
+                return node.obj
+
+            node = node.parent
+
+        return None
+
+    def ensure_object(self, object_type: t.Type[V]) -> V:
+        """Like :meth:`find_object` but sets the innermost object to a
+        new instance of `object_type` if it does not exist.
+        """
+        rv = self.find_object(object_type)
+        if rv is None:
+            self.obj = rv = object_type()
+        return rv
+
+    @t.overload
+    def lookup_default(
+        self, name: str, call: "te.Literal[True]" = True
+    ) -> t.Optional[t.Any]:
+        ...
+
+    @t.overload
+    def lookup_default(
+        self, name: str, call: "te.Literal[False]" = ...
+    ) -> t.Optional[t.Union[t.Any, t.Callable[[], t.Any]]]:
+        ...
+
+    def lookup_default(self, name: str, call: bool = True) -> t.Optional[t.Any]:
+        """Get the default for a parameter from :attr:`default_map`.
+
+        :param name: Name of the parameter.
+        :param call: If the default is a callable, call it. Disable to
+            return the callable instead.
+
+        .. versionchanged:: 8.0
+            Added the ``call`` parameter.
+        """
+        if self.default_map is not None:
+            value = self.default_map.get(name)
+
+            if call and callable(value):
+                return value()
+
+            return value
+
+        return None
+
+    def fail(self, message: str) -> "te.NoReturn":
+        """Aborts the execution of the program with a specific error
+        message.
+
+        :param message: the error message to fail with.
+        """
+        raise UsageError(message, self)
+
+    def abort(self) -> "te.NoReturn":
+        """Aborts the script."""
+        raise Abort()
+
+    def exit(self, code: int = 0) -> "te.NoReturn":
+        """Exits the application with a given exit code."""
+        raise Exit(code)
+
+    def get_usage(self) -> str:
+        """Helper method to get formatted usage string for the current
+        context and command.
+        """
+        return self.command.get_usage(self)
+
+    def get_help(self) -> str:
+        """Helper method to get formatted help page for the current
+        context and command.
+        """
+        return self.command.get_help(self)
+
+    def _make_sub_context(self, command: "Command") -> "Context":
+        """Create a new context of the same type as this context, but
+        for a new command.
+
+        :meta private:
+        """
+        return type(self)(command, info_name=command.name, parent=self)
+
+    @t.overload
+    def invoke(
+        __self,  # noqa: B902
+        __callback: "t.Callable[..., V]",
+        *args: t.Any,
+        **kwargs: t.Any,
+    ) -> V:
+        ...
+
+    @t.overload
+    def invoke(
+        __self,  # noqa: B902
+        __callback: "Command",
+        *args: t.Any,
+        **kwargs: t.Any,
+    ) -> t.Any:
+        ...
+
+    def invoke(
+        __self,  # noqa: B902
+        __callback: t.Union["Command", "t.Callable[..., V]"],
+        *args: t.Any,
+        **kwargs: t.Any,
+    ) -> t.Union[t.Any, V]:
+        """Invokes a command callback in exactly the way it expects.  There
+        are two ways to invoke this method:
+
+        1.  the first argument can be a callback and all other arguments and
+            keyword arguments are forwarded directly to the function.
+        2.  the first argument is a click command object.  In that case all
+            arguments are forwarded as well but proper click parameters
+            (options and click arguments) must be keyword arguments and Click
+            will fill in defaults.
+
+        Note that before Click 3.2 keyword arguments were not properly filled
+        in against the intention of this code and no context was created.  For
+        more information about this change and why it was done in a bugfix
+        release see :ref:`upgrade-to-3.2`.
+
+        .. versionchanged:: 8.0
+            All ``kwargs`` are tracked in :attr:`params` so they will be
+            passed if :meth:`forward` is called at multiple levels.
+        """
+        if isinstance(__callback, Command):
+            other_cmd = __callback
+
+            if other_cmd.callback is None:
+                raise TypeError(
+                    "The given command does not have a callback that can be invoked."
+                )
+            else:
+                __callback = t.cast("t.Callable[..., V]", other_cmd.callback)
+
+            ctx = __self._make_sub_context(other_cmd)
+
+            for param in other_cmd.params:
+                if param.name not in kwargs and param.expose_value:
+                    kwargs[param.name] = param.type_cast_value(  # type: ignore
+                        ctx, param.get_default(ctx)
+                    )
+
+            # Track all kwargs as params, so that forward() will pass
+            # them on in subsequent calls.
+            ctx.params.update(kwargs)
+        else:
+            ctx = __self
+
+        with augment_usage_errors(__self):
+            with ctx:
+                return __callback(*args, **kwargs)
+
+    def forward(
+        __self, __cmd: "Command", *args: t.Any, **kwargs: t.Any  # noqa: B902
+    ) -> t.Any:
+        """Similar to :meth:`invoke` but fills in default keyword
+        arguments from the current context if the other command expects
+        it.  This cannot invoke callbacks directly, only other commands.
+
+        .. versionchanged:: 8.0
+            All ``kwargs`` are tracked in :attr:`params` so they will be
+            passed if ``forward`` is called at multiple levels.
+        """
+        # Can only forward to other commands, not direct callbacks.
+        if not isinstance(__cmd, Command):
+            raise TypeError("Callback is not a command.")
+
+        for param in __self.params:
+            if param not in kwargs:
+                kwargs[param] = __self.params[param]
+
+        return __self.invoke(__cmd, *args, **kwargs)
+
+    def set_parameter_source(self, name: str, source: ParameterSource) -> None:
+        """Set the source of a parameter. This indicates the location
+        from which the value of the parameter was obtained.
+
+        :param name: The name of the parameter.
+        :param source: A member of :class:`~click.core.ParameterSource`.
+        """
+        self._parameter_source[name] = source
+
+    def get_parameter_source(self, name: str) -> t.Optional[ParameterSource]:
+        """Get the source of a parameter. This indicates the location
+        from which the value of the parameter was obtained.
+
+        This can be useful for determining when a user specified a value
+        on the command line that is the same as the default value. It
+        will be :attr:`~click.core.ParameterSource.DEFAULT` only if the
+        value was actually taken from the default.
+
+        :param name: The name of the parameter.
+        :rtype: ParameterSource
+
+        .. versionchanged:: 8.0
+            Returns ``None`` if the parameter was not provided from any
+            source.
+        """
+        return self._parameter_source.get(name)
+
+
+class BaseCommand:
+    """The base command implements the minimal API contract of commands.
+    Most code will never use this as it does not implement a lot of useful
+    functionality but it can act as the direct subclass of alternative
+    parsing methods that do not depend on the Click parser.
+
+    For instance, this can be used to bridge Click and other systems like
+    argparse or docopt.
+
+    Because base commands do not implement a lot of the API that other
+    parts of Click take for granted, they are not supported for all
+    operations.  For instance, they cannot be used with the decorators
+    usually and they have no built-in callback system.
+
+    .. versionchanged:: 2.0
+       Added the `context_settings` parameter.
+
+    :param name: the name of the command to use unless a group overrides it.
+    :param context_settings: an optional dictionary with defaults that are
+                             passed to the context object.
+    """
+
+    #: The context class to create with :meth:`make_context`.
+    #:
+    #: .. versionadded:: 8.0
+    context_class: t.Type[Context] = Context
+    #: the default for the :attr:`Context.allow_extra_args` flag.
+    allow_extra_args = False
+    #: the default for the :attr:`Context.allow_interspersed_args` flag.
+    allow_interspersed_args = True
+    #: the default for the :attr:`Context.ignore_unknown_options` flag.
+    ignore_unknown_options = False
+
+    def __init__(
+        self,
+        name: t.Optional[str],
+        context_settings: t.Optional[t.MutableMapping[str, t.Any]] = None,
+    ) -> None:
+        #: the name the command thinks it has.  Upon registering a command
+        #: on a :class:`Group` the group will default the command name
+        #: with this information.  You should instead use the
+        #: :class:`Context`\'s :attr:`~Context.info_name` attribute.
+        self.name = name
+
+        if context_settings is None:
+            context_settings = {}
+
+        #: an optional dictionary with defaults passed to the context.
+        self.context_settings: t.MutableMapping[str, t.Any] = context_settings
+
+    def to_info_dict(self, ctx: Context) -> t.Dict[str, t.Any]:
+        """Gather information that could be useful for a tool generating
+        user-facing documentation. This traverses the entire structure
+        below this command.
+
+        Use :meth:`click.Context.to_info_dict` to traverse the entire
+        CLI structure.
+
+        :param ctx: A :class:`Context` representing this command.
+
+        .. versionadded:: 8.0
+        """
+        return {"name": self.name}
+
+    def __repr__(self) -> str:
+        return f"<{self.__class__.__name__} {self.name}>"
+
+    def get_usage(self, ctx: Context) -> str:
+        raise NotImplementedError("Base commands cannot get usage")
+
+    def get_help(self, ctx: Context) -> str:
+        raise NotImplementedError("Base commands cannot get help")
+
+    def make_context(
+        self,
+        info_name: t.Optional[str],
+        args: t.List[str],
+        parent: t.Optional[Context] = None,
+        **extra: t.Any,
+    ) -> Context:
+        """This function when given an info name and arguments will kick
+        off the parsing and create a new :class:`Context`.  It does not
+        invoke the actual command callback though.
+
+        To quickly customize the context class used without overriding
+        this method, set the :attr:`context_class` attribute.
+
+        :param info_name: the info name for this invocation.  Generally this
+                          is the most descriptive name for the script or
+                          command.  For the toplevel script it's usually
+                          the name of the script, for commands below it's
+                          the name of the command.
+        :param args: the arguments to parse as list of strings.
+        :param parent: the parent context if available.
+        :param extra: extra keyword arguments forwarded to the context
+                      constructor.
+
+        .. versionchanged:: 8.0
+            Added the :attr:`context_class` attribute.
+        """
+        for key, value in self.context_settings.items():
+            if key not in extra:
+                extra[key] = value
+
+        ctx = self.context_class(
+            self, info_name=info_name, parent=parent, **extra  # type: ignore
+        )
+
+        with ctx.scope(cleanup=False):
+            self.parse_args(ctx, args)
+        return ctx
+
+    def parse_args(self, ctx: Context, args: t.List[str]) -> t.List[str]:
+        """Given a context and a list of arguments this creates the parser
+        and parses the arguments, then modifies the context as necessary.
+        This is automatically invoked by :meth:`make_context`.
+        """
+        raise NotImplementedError("Base commands do not know how to parse arguments.")
+
+    def invoke(self, ctx: Context) -> t.Any:
+        """Given a context, this invokes the command.  The default
+        implementation is raising a not implemented error.
+        """
+        raise NotImplementedError("Base commands are not invocable by default")
+
+    def shell_complete(self, ctx: Context, incomplete: str) -> t.List["CompletionItem"]:
+        """Return a list of completions for the incomplete value. Looks
+        at the names of chained multi-commands.
+
+        Any command could be part of a chained multi-command, so sibling
+        commands are valid at any point during command completion. Other
+        command classes will return more completions.
+
+        :param ctx: Invocation context for this command.
+        :param incomplete: Value being completed. May be empty.
+
+        .. versionadded:: 8.0
+        """
+        from click.shell_completion import CompletionItem
+
+        results: t.List["CompletionItem"] = []
+
+        while ctx.parent is not None:
+            ctx = ctx.parent
+
+            if isinstance(ctx.command, MultiCommand) and ctx.command.chain:
+                results.extend(
+                    CompletionItem(name, help=command.get_short_help_str())
+                    for name, command in _complete_visible_commands(ctx, incomplete)
+                    if name not in ctx.protected_args
+                )
+
+        return results
+
+    @t.overload
+    def main(
+        self,
+        args: t.Optional[t.Sequence[str]] = None,
+        prog_name: t.Optional[str] = None,
+        complete_var: t.Optional[str] = None,
+        standalone_mode: "te.Literal[True]" = True,
+        **extra: t.Any,
+    ) -> "te.NoReturn":
+        ...
+
+    @t.overload
+    def main(
+        self,
+        args: t.Optional[t.Sequence[str]] = None,
+        prog_name: t.Optional[str] = None,
+        complete_var: t.Optional[str] = None,
+        standalone_mode: bool = ...,
+        **extra: t.Any,
+    ) -> t.Any:
+        ...
+
+    def main(
+        self,
+        args: t.Optional[t.Sequence[str]] = None,
+        prog_name: t.Optional[str] = None,
+        complete_var: t.Optional[str] = None,
+        standalone_mode: bool = True,
+        windows_expand_args: bool = True,
+        **extra: t.Any,
+    ) -> t.Any:
+        """This is the way to invoke a script with all the bells and
+        whistles as a command line application.  This will always terminate
+        the application after a call.  If this is not wanted, ``SystemExit``
+        needs to be caught.
+
+        This method is also available by directly calling the instance of
+        a :class:`Command`.
+
+        :param args: the arguments that should be used for parsing.  If not
+                     provided, ``sys.argv[1:]`` is used.
+        :param prog_name: the program name that should be used.  By default
+                          the program name is constructed by taking the file
+                          name from ``sys.argv[0]``.
+        :param complete_var: the environment variable that controls the
+                             bash completion support.  The default is
+                             ``"_<prog_name>_COMPLETE"`` with prog_name in
+                             uppercase.
+        :param standalone_mode: the default behavior is to invoke the script
+                                in standalone mode.  Click will then
+                                handle exceptions and convert them into
+                                error messages and the function will never
+                                return but shut down the interpreter.  If
+                                this is set to `False` they will be
+                                propagated to the caller and the return
+                                value of this function is the return value
+                                of :meth:`invoke`.
+        :param windows_expand_args: Expand glob patterns, user dir, and
+            env vars in command line args on Windows.
+        :param extra: extra keyword arguments are forwarded to the context
+                      constructor.  See :class:`Context` for more information.
+
+        .. versionchanged:: 8.0.1
+            Added the ``windows_expand_args`` parameter to allow
+            disabling command line arg expansion on Windows.
+
+        .. versionchanged:: 8.0
+            When taking arguments from ``sys.argv`` on Windows, glob
+            patterns, user dir, and env vars are expanded.
+
+        .. versionchanged:: 3.0
+           Added the ``standalone_mode`` parameter.
+        """
+        if args is None:
+            args = sys.argv[1:]
+
+            if os.name == "nt" and windows_expand_args:
+                args = _expand_args(args)
+        else:
+            args = list(args)
+
+        if prog_name is None:
+            prog_name = _detect_program_name()
+
+        # Process shell completion requests and exit early.
+        self._main_shell_completion(extra, prog_name, complete_var)
+
+        try:
+            try:
+                with self.make_context(prog_name, args, **extra) as ctx:
+                    rv = self.invoke(ctx)
+                    if not standalone_mode:
+                        return rv
+                    # it's not safe to `ctx.exit(rv)` here!
+                    # note that `rv` may actually contain data like "1" which
+                    # has obvious effects
+                    # more subtle case: `rv=[None, None]` can come out of
+                    # chained commands which all returned `None` -- so it's not
+                    # even always obvious that `rv` indicates success/failure
+                    # by its truthiness/falsiness
+                    ctx.exit()
+            except (EOFError, KeyboardInterrupt) as e:
+                echo(file=sys.stderr)
+                raise Abort() from e
+            except ClickException as e:
+                if not standalone_mode:
+                    raise
+                e.show()
+                sys.exit(e.exit_code)
+            except OSError as e:
+                if e.errno == errno.EPIPE:
+                    sys.stdout = t.cast(t.TextIO, PacifyFlushWrapper(sys.stdout))
+                    sys.stderr = t.cast(t.TextIO, PacifyFlushWrapper(sys.stderr))
+                    sys.exit(1)
+                else:
+                    raise
+        except Exit as e:
+            if standalone_mode:
+                sys.exit(e.exit_code)
+            else:
+                # in non-standalone mode, return the exit code
+                # note that this is only reached if `self.invoke` above raises
+                # an Exit explicitly -- thus bypassing the check there which
+                # would return its result
+                # the results of non-standalone execution may therefore be
+                # somewhat ambiguous: if there are codepaths which lead to
+                # `ctx.exit(1)` and to `return 1`, the caller won't be able to
+                # tell the difference between the two
+                return e.exit_code
+        except Abort:
+            if not standalone_mode:
+                raise
+            echo(_("Aborted!"), file=sys.stderr)
+            sys.exit(1)
+
+    def _main_shell_completion(
+        self,
+        ctx_args: t.MutableMapping[str, t.Any],
+        prog_name: str,
+        complete_var: t.Optional[str] = None,
+    ) -> None:
+        """Check if the shell is asking for tab completion, process
+        that, then exit early. Called from :meth:`main` before the
+        program is invoked.
+
+        :param prog_name: Name of the executable in the shell.
+        :param complete_var: Name of the environment variable that holds
+            the completion instruction. Defaults to
+            ``_{PROG_NAME}_COMPLETE``.
+
+        .. versionchanged:: 8.2.0
+            Dots (``.``) in ``prog_name`` are replaced with underscores (``_``).
+        """
+        if complete_var is None:
+            complete_name = prog_name.replace("-", "_").replace(".", "_")
+            complete_var = f"_{complete_name}_COMPLETE".upper()
+
+        instruction = os.environ.get(complete_var)
+
+        if not instruction:
+            return
+
+        from .shell_completion import shell_complete
+
+        rv = shell_complete(self, ctx_args, prog_name, complete_var, instruction)
+        sys.exit(rv)
+
+    def __call__(self, *args: t.Any, **kwargs: t.Any) -> t.Any:
+        """Alias for :meth:`main`."""
+        return self.main(*args, **kwargs)
+
+
+class Command(BaseCommand):
+    """Commands are the basic building block of command line interfaces in
+    Click.  A basic command handles command line parsing and might dispatch
+    more parsing to commands nested below it.
+
+    :param name: the name of the command to use unless a group overrides it.
+    :param context_settings: an optional dictionary with defaults that are
+                             passed to the context object.
+    :param callback: the callback to invoke.  This is optional.
+    :param params: the parameters to register with this command.  This can
+                   be either :class:`Option` or :class:`Argument` objects.
+    :param help: the help string to use for this command.
+    :param epilog: like the help string but it's printed at the end of the
+                   help page after everything else.
+    :param short_help: the short help to use for this command.  This is
+                       shown on the command listing of the parent command.
+    :param add_help_option: by default each command registers a ``--help``
+                            option.  This can be disabled by this parameter.
+    :param no_args_is_help: this controls what happens if no arguments are
+                            provided.  This option is disabled by default.
+                            If enabled this will add ``--help`` as argument
+                            if no arguments are passed
+    :param hidden: hide this command from help outputs.
+
+    :param deprecated: issues a message indicating that
+                             the command is deprecated.
+
+    .. versionchanged:: 8.1
+        ``help``, ``epilog``, and ``short_help`` are stored unprocessed,
+        all formatting is done when outputting help text, not at init,
+        and is done even if not using the ``@command`` decorator.
+
+    .. versionchanged:: 8.0
+        Added a ``repr`` showing the command name.
+
+    .. versionchanged:: 7.1
+        Added the ``no_args_is_help`` parameter.
+
+    .. versionchanged:: 2.0
+        Added the ``context_settings`` parameter.
+    """
+
+    def __init__(
+        self,
+        name: t.Optional[str],
+        context_settings: t.Optional[t.MutableMapping[str, t.Any]] = None,
+        callback: t.Optional[t.Callable[..., t.Any]] = None,
+        params: t.Optional[t.List["Parameter"]] = None,
+        help: t.Optional[str] = None,
+        epilog: t.Optional[str] = None,
+        short_help: t.Optional[str] = None,
+        options_metavar: t.Optional[str] = "[OPTIONS]",
+        add_help_option: bool = True,
+        no_args_is_help: bool = False,
+        hidden: bool = False,
+        deprecated: bool = False,
+    ) -> None:
+        super().__init__(name, context_settings)
+        #: the callback to execute when the command fires.  This might be
+        #: `None` in which case nothing happens.
+        self.callback = callback
+        #: the list of parameters for this command in the order they
+        #: should show up in the help page and execute.  Eager parameters
+        #: will automatically be handled before non eager ones.
+        self.params: t.List["Parameter"] = params or []
+        self.help = help
+        self.epilog = epilog
+        self.options_metavar = options_metavar
+        self.short_help = short_help
+        self.add_help_option = add_help_option
+        self.no_args_is_help = no_args_is_help
+        self.hidden = hidden
+        self.deprecated = deprecated
+
+    def to_info_dict(self, ctx: Context) -> t.Dict[str, t.Any]:
+        info_dict = super().to_info_dict(ctx)
+        info_dict.update(
+            params=[param.to_info_dict() for param in self.get_params(ctx)],
+            help=self.help,
+            epilog=self.epilog,
+            short_help=self.short_help,
+            hidden=self.hidden,
+            deprecated=self.deprecated,
+        )
+        return info_dict
+
+    def get_usage(self, ctx: Context) -> str:
+        """Formats the usage line into a string and returns it.
+
+        Calls :meth:`format_usage` internally.
+        """
+        formatter = ctx.make_formatter()
+        self.format_usage(ctx, formatter)
+        return formatter.getvalue().rstrip("\n")
+
+    def get_params(self, ctx: Context) -> t.List["Parameter"]:
+        rv = self.params
+        help_option = self.get_help_option(ctx)
+
+        if help_option is not None:
+            rv = [*rv, help_option]
+
+        return rv
+
+    def format_usage(self, ctx: Context, formatter: HelpFormatter) -> None:
+        """Writes the usage line into the formatter.
+
+        This is a low-level method called by :meth:`get_usage`.
+        """
+        pieces = self.collect_usage_pieces(ctx)
+        formatter.write_usage(ctx.command_path, " ".join(pieces))
+
+    def collect_usage_pieces(self, ctx: Context) -> t.List[str]:
+        """Returns all the pieces that go into the usage line and returns
+        it as a list of strings.
+        """
+        rv = [self.options_metavar] if self.options_metavar else []
+
+        for param in self.get_params(ctx):
+            rv.extend(param.get_usage_pieces(ctx))
+
+        return rv
+
+    def get_help_option_names(self, ctx: Context) -> t.List[str]:
+        """Returns the names for the help option."""
+        all_names = set(ctx.help_option_names)
+        for param in self.params:
+            all_names.difference_update(param.opts)
+            all_names.difference_update(param.secondary_opts)
+        return list(all_names)
+
+    def get_help_option(self, ctx: Context) -> t.Optional["Option"]:
+        """Returns the help option object."""
+        help_options = self.get_help_option_names(ctx)
+
+        if not help_options or not self.add_help_option:
+            return None
+
+        def show_help(ctx: Context, param: "Parameter", value: str) -> None:
+            if value and not ctx.resilient_parsing:
+                echo(ctx.get_help(), color=ctx.color)
+                ctx.exit()
+
+        return Option(
+            help_options,
+            is_flag=True,
+            is_eager=True,
+            expose_value=False,
+            callback=show_help,
+            help=_("Show this message and exit."),
+        )
+
+    def make_parser(self, ctx: Context) -> OptionParser:
+        """Creates the underlying option parser for this command."""
+        parser = OptionParser(ctx)
+        for param in self.get_params(ctx):
+            param.add_to_parser(parser, ctx)
+        return parser
+
+    def get_help(self, ctx: Context) -> str:
+        """Formats the help into a string and returns it.
+
+        Calls :meth:`format_help` internally.
+        """
+        formatter = ctx.make_formatter()
+        self.format_help(ctx, formatter)
+        return formatter.getvalue().rstrip("\n")
+
+    def get_short_help_str(self, limit: int = 45) -> str:
+        """Gets short help for the command or makes it by shortening the
+        long help string.
+        """
+        if self.short_help:
+            text = inspect.cleandoc(self.short_help)
+        elif self.help:
+            text = make_default_short_help(self.help, limit)
+        else:
+            text = ""
+
+        if self.deprecated:
+            text = _("(Deprecated) {text}").format(text=text)
+
+        return text.strip()
+
+    def format_help(self, ctx: Context, formatter: HelpFormatter) -> None:
+        """Writes the help into the formatter if it exists.
+
+        This is a low-level method called by :meth:`get_help`.
+
+        This calls the following methods:
+
+        -   :meth:`format_usage`
+        -   :meth:`format_help_text`
+        -   :meth:`format_options`
+        -   :meth:`format_epilog`
+        """
+        self.format_usage(ctx, formatter)
+        self.format_help_text(ctx, formatter)
+        self.format_options(ctx, formatter)
+        self.format_epilog(ctx, formatter)
+
+    def format_help_text(self, ctx: Context, formatter: HelpFormatter) -> None:
+        """Writes the help text to the formatter if it exists."""
+        if self.help is not None:
+            # truncate the help text to the first form feed
+            text = inspect.cleandoc(self.help).partition("\f")[0]
+        else:
+            text = ""
+
+        if self.deprecated:
+            text = _("(Deprecated) {text}").format(text=text)
+
+        if text:
+            formatter.write_paragraph()
+
+            with formatter.indentation():
+                formatter.write_text(text)
+
+    def format_options(self, ctx: Context, formatter: HelpFormatter) -> None:
+        """Writes all the options into the formatter if they exist."""
+        opts = []
+        for param in self.get_params(ctx):
+            rv = param.get_help_record(ctx)
+            if rv is not None:
+                opts.append(rv)
+
+        if opts:
+            with formatter.section(_("Options")):
+                formatter.write_dl(opts)
+
+    def format_epilog(self, ctx: Context, formatter: HelpFormatter) -> None:
+        """Writes the epilog into the formatter if it exists."""
+        if self.epilog:
+            epilog = inspect.cleandoc(self.epilog)
+            formatter.write_paragraph()
+
+            with formatter.indentation():
+                formatter.write_text(epilog)
+
+    def parse_args(self, ctx: Context, args: t.List[str]) -> t.List[str]:
+        if not args and self.no_args_is_help and not ctx.resilient_parsing:
+            echo(ctx.get_help(), color=ctx.color)
+            ctx.exit()
+
+        parser = self.make_parser(ctx)
+        opts, args, param_order = parser.parse_args(args=args)
+
+        for param in iter_params_for_processing(param_order, self.get_params(ctx)):
+            value, args = param.handle_parse_result(ctx, opts, args)
+
+        if args and not ctx.allow_extra_args and not ctx.resilient_parsing:
+            ctx.fail(
+                ngettext(
+                    "Got unexpected extra argument ({args})",
+                    "Got unexpected extra arguments ({args})",
+                    len(args),
+                ).format(args=" ".join(map(str, args)))
+            )
+
+        ctx.args = args
+        ctx._opt_prefixes.update(parser._opt_prefixes)
+        return args
+
+    def invoke(self, ctx: Context) -> t.Any:
+        """Given a context, this invokes the attached callback (if it exists)
+        in the right way.
+        """
+        if self.deprecated:
+            message = _(
+                "DeprecationWarning: The command {name!r} is deprecated."
+            ).format(name=self.name)
+            echo(style(message, fg="red"), err=True)
+
+        if self.callback is not None:
+            return ctx.invoke(self.callback, **ctx.params)
+
+    def shell_complete(self, ctx: Context, incomplete: str) -> t.List["CompletionItem"]:
+        """Return a list of completions for the incomplete value. Looks
+        at the names of options and chained multi-commands.
+
+        :param ctx: Invocation context for this command.
+        :param incomplete: Value being completed. May be empty.
+
+        .. versionadded:: 8.0
+        """
+        from click.shell_completion import CompletionItem
+
+        results: t.List["CompletionItem"] = []
+
+        if incomplete and not incomplete[0].isalnum():
+            for param in self.get_params(ctx):
+                if (
+                    not isinstance(param, Option)
+                    or param.hidden
+                    or (
+                        not param.multiple
+                        and ctx.get_parameter_source(param.name)  # type: ignore
+                        is ParameterSource.COMMANDLINE
+                    )
+                ):
+                    continue
+
+                results.extend(
+                    CompletionItem(name, help=param.help)
+                    for name in [*param.opts, *param.secondary_opts]
+                    if name.startswith(incomplete)
+                )
+
+        results.extend(super().shell_complete(ctx, incomplete))
+        return results
+
+
+class MultiCommand(Command):
+    """A multi command is the basic implementation of a command that
+    dispatches to subcommands.  The most common version is the
+    :class:`Group`.
+
+    :param invoke_without_command: this controls how the multi command itself
+                                   is invoked.  By default it's only invoked
+                                   if a subcommand is provided.
+    :param no_args_is_help: this controls what happens if no arguments are
+                            provided.  This option is enabled by default if
+                            `invoke_without_command` is disabled or disabled
+                            if it's enabled.  If enabled this will add
+                            ``--help`` as argument if no arguments are
+                            passed.
+    :param subcommand_metavar: the string that is used in the documentation
+                               to indicate the subcommand place.
+    :param chain: if this is set to `True` chaining of multiple subcommands
+                  is enabled.  This restricts the form of commands in that
+                  they cannot have optional arguments but it allows
+                  multiple commands to be chained together.
+    :param result_callback: The result callback to attach to this multi
+        command. This can be set or changed later with the
+        :meth:`result_callback` decorator.
+    :param attrs: Other command arguments described in :class:`Command`.
+    """
+
+    allow_extra_args = True
+    allow_interspersed_args = False
+
+    def __init__(
+        self,
+        name: t.Optional[str] = None,
+        invoke_without_command: bool = False,
+        no_args_is_help: t.Optional[bool] = None,
+        subcommand_metavar: t.Optional[str] = None,
+        chain: bool = False,
+        result_callback: t.Optional[t.Callable[..., t.Any]] = None,
+        **attrs: t.Any,
+    ) -> None:
+        super().__init__(name, **attrs)
+
+        if no_args_is_help is None:
+            no_args_is_help = not invoke_without_command
+
+        self.no_args_is_help = no_args_is_help
+        self.invoke_without_command = invoke_without_command
+
+        if subcommand_metavar is None:
+            if chain:
+                subcommand_metavar = "COMMAND1 [ARGS]... [COMMAND2 [ARGS]...]..."
+            else:
+                subcommand_metavar = "COMMAND [ARGS]..."
+
+        self.subcommand_metavar = subcommand_metavar
+        self.chain = chain
+        # The result callback that is stored. This can be set or
+        # overridden with the :func:`result_callback` decorator.
+        self._result_callback = result_callback
+
+        if self.chain:
+            for param in self.params:
+                if isinstance(param, Argument) and not param.required:
+                    raise RuntimeError(
+                        "Multi commands in chain mode cannot have"
+                        " optional arguments."
+                    )
+
+    def to_info_dict(self, ctx: Context) -> t.Dict[str, t.Any]:
+        info_dict = super().to_info_dict(ctx)
+        commands = {}
+
+        for name in self.list_commands(ctx):
+            command = self.get_command(ctx, name)
+
+            if command is None:
+                continue
+
+            sub_ctx = ctx._make_sub_context(command)
+
+            with sub_ctx.scope(cleanup=False):
+                commands[name] = command.to_info_dict(sub_ctx)
+
+        info_dict.update(commands=commands, chain=self.chain)
+        return info_dict
+
+    def collect_usage_pieces(self, ctx: Context) -> t.List[str]:
+        rv = super().collect_usage_pieces(ctx)
+        rv.append(self.subcommand_metavar)
+        return rv
+
+    def format_options(self, ctx: Context, formatter: HelpFormatter) -> None:
+        super().format_options(ctx, formatter)
+        self.format_commands(ctx, formatter)
+
+    def result_callback(self, replace: bool = False) -> t.Callable[[F], F]:
+        """Adds a result callback to the command.  By default if a
+        result callback is already registered this will chain them but
+        this can be disabled with the `replace` parameter.  The result
+        callback is invoked with the return value of the subcommand
+        (or the list of return values from all subcommands if chaining
+        is enabled) as well as the parameters as they would be passed
+        to the main callback.
+
+        Example::
+
+            @click.group()
+            @click.option('-i', '--input', default=23)
+            def cli(input):
+                return 42
+
+            @cli.result_callback()
+            def process_result(result, input):
+                return result + input
+
+        :param replace: if set to `True` an already existing result
+                        callback will be removed.
+
+        .. versionchanged:: 8.0
+            Renamed from ``resultcallback``.
+
+        .. versionadded:: 3.0
+        """
+
+        def decorator(f: F) -> F:
+            old_callback = self._result_callback
+
+            if old_callback is None or replace:
+                self._result_callback = f
+                return f
+
+            def function(__value, *args, **kwargs):  # type: ignore
+                inner = old_callback(__value, *args, **kwargs)
+                return f(inner, *args, **kwargs)
+
+            self._result_callback = rv = update_wrapper(t.cast(F, function), f)
+            return rv
+
+        return decorator
+
+    def format_commands(self, ctx: Context, formatter: HelpFormatter) -> None:
+        """Extra format methods for multi methods that adds all the commands
+        after the options.
+        """
+        commands = []
+        for subcommand in self.list_commands(ctx):
+            cmd = self.get_command(ctx, subcommand)
+            # What is this, the tool lied about a command.  Ignore it
+            if cmd is None:
+                continue
+            if cmd.hidden:
+                continue
+
+            commands.append((subcommand, cmd))
+
+        # allow for 3 times the default spacing
+        if len(commands):
+            limit = formatter.width - 6 - max(len(cmd[0]) for cmd in commands)
+
+            rows = []
+            for subcommand, cmd in commands:
+                help = cmd.get_short_help_str(limit)
+                rows.append((subcommand, help))
+
+            if rows:
+                with formatter.section(_("Commands")):
+                    formatter.write_dl(rows)
+
+    def parse_args(self, ctx: Context, args: t.List[str]) -> t.List[str]:
+        if not args and self.no_args_is_help and not ctx.resilient_parsing:
+            echo(ctx.get_help(), color=ctx.color)
+            ctx.exit()
+
+        rest = super().parse_args(ctx, args)
+
+        if self.chain:
+            ctx.protected_args = rest
+            ctx.args = []
+        elif rest:
+            ctx.protected_args, ctx.args = rest[:1], rest[1:]
+
+        return ctx.args
+
+    def invoke(self, ctx: Context) -> t.Any:
+        def _process_result(value: t.Any) -> t.Any:
+            if self._result_callback is not None:
+                value = ctx.invoke(self._result_callback, value, **ctx.params)
+            return value
+
+        if not ctx.protected_args:
+            if self.invoke_without_command:
+                # No subcommand was invoked, so the result callback is
+                # invoked with the group return value for regular
+                # groups, or an empty list for chained groups.
+                with ctx:
+                    rv = super().invoke(ctx)
+                    return _process_result([] if self.chain else rv)
+            ctx.fail(_("Missing command."))
+
+        # Fetch args back out
+        args = [*ctx.protected_args, *ctx.args]
+        ctx.args = []
+        ctx.protected_args = []
+
+        # If we're not in chain mode, we only allow the invocation of a
+        # single command but we also inform the current context about the
+        # name of the command to invoke.
+        if not self.chain:
+            # Make sure the context is entered so we do not clean up
+            # resources until the result processor has worked.
+            with ctx:
+                cmd_name, cmd, args = self.resolve_command(ctx, args)
+                assert cmd is not None
+                ctx.invoked_subcommand = cmd_name
+                super().invoke(ctx)
+                sub_ctx = cmd.make_context(cmd_name, args, parent=ctx)
+                with sub_ctx:
+                    return _process_result(sub_ctx.command.invoke(sub_ctx))
+
+        # In chain mode we create the contexts step by step, but after the
+        # base command has been invoked.  Because at that point we do not
+        # know the subcommands yet, the invoked subcommand attribute is
+        # set to ``*`` to inform the command that subcommands are executed
+        # but nothing else.
+        with ctx:
+            ctx.invoked_subcommand = "*" if args else None
+            super().invoke(ctx)
+
+            # Otherwise we make every single context and invoke them in a
+            # chain.  In that case the return value to the result processor
+            # is the list of all invoked subcommand's results.
+            contexts = []
+            while args:
+                cmd_name, cmd, args = self.resolve_command(ctx, args)
+                assert cmd is not None
+                sub_ctx = cmd.make_context(
+                    cmd_name,
+                    args,
+                    parent=ctx,
+                    allow_extra_args=True,
+                    allow_interspersed_args=False,
+                )
+                contexts.append(sub_ctx)
+                args, sub_ctx.args = sub_ctx.args, []
+
+            rv = []
+            for sub_ctx in contexts:
+                with sub_ctx:
+                    rv.append(sub_ctx.command.invoke(sub_ctx))
+            return _process_result(rv)
+
+    def resolve_command(
+        self, ctx: Context, args: t.List[str]
+    ) -> t.Tuple[t.Optional[str], t.Optional[Command], t.List[str]]:
+        cmd_name = make_str(args[0])
+        original_cmd_name = cmd_name
+
+        # Get the command
+        cmd = self.get_command(ctx, cmd_name)
+
+        # If we can't find the command but there is a normalization
+        # function available, we try with that one.
+        if cmd is None and ctx.token_normalize_func is not None:
+            cmd_name = ctx.token_normalize_func(cmd_name)
+            cmd = self.get_command(ctx, cmd_name)
+
+        # If we don't find the command we want to show an error message
+        # to the user that it was not provided.  However, there is
+        # something else we should do: if the first argument looks like
+        # an option we want to kick off parsing again for arguments to
+        # resolve things like --help which now should go to the main
+        # place.
+        if cmd is None and not ctx.resilient_parsing:
+            if split_opt(cmd_name)[0]:
+                self.parse_args(ctx, ctx.args)
+            ctx.fail(_("No such command {name!r}.").format(name=original_cmd_name))
+        return cmd_name if cmd else None, cmd, args[1:]
+
+    def get_command(self, ctx: Context, cmd_name: str) -> t.Optional[Command]:
+        """Given a context and a command name, this returns a
+        :class:`Command` object if it exists or returns `None`.
+        """
+        raise NotImplementedError
+
+    def list_commands(self, ctx: Context) -> t.List[str]:
+        """Returns a list of subcommand names in the order they should
+        appear.
+        """
+        return []
+
+    def shell_complete(self, ctx: Context, incomplete: str) -> t.List["CompletionItem"]:
+        """Return a list of completions for the incomplete value. Looks
+        at the names of options, subcommands, and chained
+        multi-commands.
+
+        :param ctx: Invocation context for this command.
+        :param incomplete: Value being completed. May be empty.
+
+        .. versionadded:: 8.0
+        """
+        from click.shell_completion import CompletionItem
+
+        results = [
+            CompletionItem(name, help=command.get_short_help_str())
+            for name, command in _complete_visible_commands(ctx, incomplete)
+        ]
+        results.extend(super().shell_complete(ctx, incomplete))
+        return results
+
+
+class Group(MultiCommand):
+    """A group allows a command to have subcommands attached. This is
+    the most common way to implement nesting in Click.
+
+    :param name: The name of the group command.
+    :param commands: A dict mapping names to :class:`Command` objects.
+        Can also be a list of :class:`Command`, which will use
+        :attr:`Command.name` to create the dict.
+    :param attrs: Other command arguments described in
+        :class:`MultiCommand`, :class:`Command`, and
+        :class:`BaseCommand`.
+
+    .. versionchanged:: 8.0
+        The ``commands`` argument can be a list of command objects.
+    """
+
+    #: If set, this is used by the group's :meth:`command` decorator
+    #: as the default :class:`Command` class. This is useful to make all
+    #: subcommands use a custom command class.
+    #:
+    #: .. versionadded:: 8.0
+    command_class: t.Optional[t.Type[Command]] = None
+
+    #: If set, this is used by the group's :meth:`group` decorator
+    #: as the default :class:`Group` class. This is useful to make all
+    #: subgroups use a custom group class.
+    #:
+    #: If set to the special value :class:`type` (literally
+    #: ``group_class = type``), this group's class will be used as the
+    #: default class. This makes a custom group class continue to make
+    #: custom groups.
+    #:
+    #: .. versionadded:: 8.0
+    group_class: t.Optional[t.Union[t.Type["Group"], t.Type[type]]] = None
+    # Literal[type] isn't valid, so use Type[type]
+
+    def __init__(
+        self,
+        name: t.Optional[str] = None,
+        commands: t.Optional[
+            t.Union[t.MutableMapping[str, Command], t.Sequence[Command]]
+        ] = None,
+        **attrs: t.Any,
+    ) -> None:
+        super().__init__(name, **attrs)
+
+        if commands is None:
+            commands = {}
+        elif isinstance(commands, abc.Sequence):
+            commands = {c.name: c for c in commands if c.name is not None}
+
+        #: The registered subcommands by their exported names.
+        self.commands: t.MutableMapping[str, Command] = commands
+
+    def add_command(self, cmd: Command, name: t.Optional[str] = None) -> None:
+        """Registers another :class:`Command` with this group.  If the name
+        is not provided, the name of the command is used.
+        """
+        name = name or cmd.name
+        if name is None:
+            raise TypeError("Command has no name.")
+        _check_multicommand(self, name, cmd, register=True)
+        self.commands[name] = cmd
+
+    @t.overload
+    def command(self, __func: t.Callable[..., t.Any]) -> Command:
+        ...
+
+    @t.overload
+    def command(
+        self, *args: t.Any, **kwargs: t.Any
+    ) -> t.Callable[[t.Callable[..., t.Any]], Command]:
+        ...
+
+    def command(
+        self, *args: t.Any, **kwargs: t.Any
+    ) -> t.Union[t.Callable[[t.Callable[..., t.Any]], Command], Command]:
+        """A shortcut decorator for declaring and attaching a command to
+        the group. This takes the same arguments as :func:`command` and
+        immediately registers the created command with this group by
+        calling :meth:`add_command`.
+
+        To customize the command class used, set the
+        :attr:`command_class` attribute.
+
+        .. versionchanged:: 8.1
+            This decorator can be applied without parentheses.
+
+        .. versionchanged:: 8.0
+            Added the :attr:`command_class` attribute.
+        """
+        from .decorators import command
+
+        func: t.Optional[t.Callable[..., t.Any]] = None
+
+        if args and callable(args[0]):
+            assert (
+                len(args) == 1 and not kwargs
+            ), "Use 'command(**kwargs)(callable)' to provide arguments."
+            (func,) = args
+            args = ()
+
+        if self.command_class and kwargs.get("cls") is None:
+            kwargs["cls"] = self.command_class
+
+        def decorator(f: t.Callable[..., t.Any]) -> Command:
+            cmd: Command = command(*args, **kwargs)(f)
+            self.add_command(cmd)
+            return cmd
+
+        if func is not None:
+            return decorator(func)
+
+        return decorator
+
+    @t.overload
+    def group(self, __func: t.Callable[..., t.Any]) -> "Group":
+        ...
+
+    @t.overload
+    def group(
+        self, *args: t.Any, **kwargs: t.Any
+    ) -> t.Callable[[t.Callable[..., t.Any]], "Group"]:
+        ...
+
+    def group(
+        self, *args: t.Any, **kwargs: t.Any
+    ) -> t.Union[t.Callable[[t.Callable[..., t.Any]], "Group"], "Group"]:
+        """A shortcut decorator for declaring and attaching a group to
+        the group. This takes the same arguments as :func:`group` and
+        immediately registers the created group with this group by
+        calling :meth:`add_command`.
+
+        To customize the group class used, set the :attr:`group_class`
+        attribute.
+
+        .. versionchanged:: 8.1
+            This decorator can be applied without parentheses.
+
+        .. versionchanged:: 8.0
+            Added the :attr:`group_class` attribute.
+        """
+        from .decorators import group
+
+        func: t.Optional[t.Callable[..., t.Any]] = None
+
+        if args and callable(args[0]):
+            assert (
+                len(args) == 1 and not kwargs
+            ), "Use 'group(**kwargs)(callable)' to provide arguments."
+            (func,) = args
+            args = ()
+
+        if self.group_class is not None and kwargs.get("cls") is None:
+            if self.group_class is type:
+                kwargs["cls"] = type(self)
+            else:
+                kwargs["cls"] = self.group_class
+
+        def decorator(f: t.Callable[..., t.Any]) -> "Group":
+            cmd: Group = group(*args, **kwargs)(f)
+            self.add_command(cmd)
+            return cmd
+
+        if func is not None:
+            return decorator(func)
+
+        return decorator
+
+    def get_command(self, ctx: Context, cmd_name: str) -> t.Optional[Command]:
+        return self.commands.get(cmd_name)
+
+    def list_commands(self, ctx: Context) -> t.List[str]:
+        return sorted(self.commands)
+
+
+class CommandCollection(MultiCommand):
+    """A command collection is a multi command that merges multiple multi
+    commands together into one.  This is a straightforward implementation
+    that accepts a list of different multi commands as sources and
+    provides all the commands for each of them.
+
+    See :class:`MultiCommand` and :class:`Command` for the description of
+    ``name`` and ``attrs``.
+    """
+
+    def __init__(
+        self,
+        name: t.Optional[str] = None,
+        sources: t.Optional[t.List[MultiCommand]] = None,
+        **attrs: t.Any,
+    ) -> None:
+        super().__init__(name, **attrs)
+        #: The list of registered multi commands.
+        self.sources: t.List[MultiCommand] = sources or []
+
+    def add_source(self, multi_cmd: MultiCommand) -> None:
+        """Adds a new multi command to the chain dispatcher."""
+        self.sources.append(multi_cmd)
+
+    def get_command(self, ctx: Context, cmd_name: str) -> t.Optional[Command]:
+        for source in self.sources:
+            rv = source.get_command(ctx, cmd_name)
+
+            if rv is not None:
+                if self.chain:
+                    _check_multicommand(self, cmd_name, rv)
+
+                return rv
+
+        return None
+
+    def list_commands(self, ctx: Context) -> t.List[str]:
+        rv: t.Set[str] = set()
+
+        for source in self.sources:
+            rv.update(source.list_commands(ctx))
+
+        return sorted(rv)
+
+
+def _check_iter(value: t.Any) -> t.Iterator[t.Any]:
+    """Check if the value is iterable but not a string. Raises a type
+    error, or return an iterator over the value.
+    """
+    if isinstance(value, str):
+        raise TypeError
+
+    return iter(value)
+
+
+class Parameter:
+    r"""A parameter to a command comes in two versions: they are either
+    :class:`Option`\s or :class:`Argument`\s.  Other subclasses are currently
+    not supported by design as some of the internals for parsing are
+    intentionally not finalized.
+
+    Some settings are supported by both options and arguments.
+
+    :param param_decls: the parameter declarations for this option or
+                        argument.  This is a list of flags or argument
+                        names.
+    :param type: the type that should be used.  Either a :class:`ParamType`
+                 or a Python type.  The latter is converted into the former
+                 automatically if supported.
+    :param required: controls if this is optional or not.
+    :param default: the default value if omitted.  This can also be a callable,
+                    in which case it's invoked when the default is needed
+                    without any arguments.
+    :param callback: A function to further process or validate the value
+        after type conversion. It is called as ``f(ctx, param, value)``
+        and must return the value. It is called for all sources,
+        including prompts.
+    :param nargs: the number of arguments to match.  If not ``1`` the return
+                  value is a tuple instead of single value.  The default for
+                  nargs is ``1`` (except if the type is a tuple, then it's
+                  the arity of the tuple). If ``nargs=-1``, all remaining
+                  parameters are collected.
+    :param metavar: how the value is represented in the help page.
+    :param expose_value: if this is `True` then the value is passed onwards
+                         to the command callback and stored on the context,
+                         otherwise it's skipped.
+    :param is_eager: eager values are processed before non eager ones.  This
+                     should not be set for arguments or it will inverse the
+                     order of processing.
+    :param envvar: a string or list of strings that are environment variables
+                   that should be checked.
+    :param shell_complete: A function that returns custom shell
+        completions. Used instead of the param's type completion if
+        given. Takes ``ctx, param, incomplete`` and must return a list
+        of :class:`~click.shell_completion.CompletionItem` or a list of
+        strings.
+
+    .. 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.
+    """
+
+    param_type_name = "parameter"
+
+    def __init__(
+        self,
+        param_decls: t.Optional[t.Sequence[str]] = None,
+        type: t.Optional[t.Union[types.ParamType, t.Any]] = None,
+        required: bool = False,
+        default: t.Optional[t.Union[t.Any, t.Callable[[], t.Any]]] = None,
+        callback: t.Optional[t.Callable[[Context, "Parameter", t.Any], t.Any]] = None,
+        nargs: t.Optional[int] = None,
+        multiple: bool = False,
+        metavar: t.Optional[str] = None,
+        expose_value: bool = True,
+        is_eager: bool = False,
+        envvar: t.Optional[t.Union[str, t.Sequence[str]]] = None,
+        shell_complete: t.Optional[
+            t.Callable[
+                [Context, "Parameter", str],
+                t.Union[t.List["CompletionItem"], t.List[str]],
+            ]
+        ] = None,
+    ) -> None:
+        self.name: t.Optional[str]
+        self.opts: t.List[str]
+        self.secondary_opts: t.List[str]
+        self.name, self.opts, self.secondary_opts = self._parse_decls(
+            param_decls or (), expose_value
+        )
+        self.type: types.ParamType = types.convert_type(type, default)
+
+        # Default nargs to what the type tells us if we have that
+        # information available.
+        if nargs is None:
+            if self.type.is_composite:
+                nargs = self.type.arity
+            else:
+                nargs = 1
+
+        self.required = required
+        self.callback = callback
+        self.nargs = nargs
+        self.multiple = multiple
+        self.expose_value = expose_value
+        self.default = default
+        self.is_eager = is_eager
+        self.metavar = metavar
+        self.envvar = envvar
+        self._custom_shell_complete = shell_complete
+
+        if __debug__:
+            if self.type.is_composite and nargs != self.type.arity:
+                raise ValueError(
+                    f"'nargs' must be {self.type.arity} (or None) for"
+                    f" type {self.type!r}, but it was {nargs}."
+                )
+
+            # Skip no default or callable default.
+            check_default = default if not callable(default) else None
+
+            if check_default is not None:
+                if multiple:
+                    try:
+                        # Only check the first value against nargs.
+                        check_default = next(_check_iter(check_default), None)
+                    except TypeError:
+                        raise ValueError(
+                            "'default' must be a list when 'multiple' is true."
+                        ) from None
+
+                # Can be None for multiple with empty default.
+                if nargs != 1 and check_default is not None:
+                    try:
+                        _check_iter(check_default)
+                    except TypeError:
+                        if multiple:
+                            message = (
+                                "'default' must be a list of lists when 'multiple' is"
+                                " true and 'nargs' != 1."
+                            )
+                        else:
+                            message = "'default' must be a list when 'nargs' != 1."
+
+                        raise ValueError(message) from None
+
+                    if nargs > 1 and len(check_default) != nargs:
+                        subject = "item length" if multiple else "length"
+                        raise ValueError(
+                            f"'default' {subject} must match nargs={nargs}."
+                        )
+
+    def to_info_dict(self) -> t.Dict[str, t.Any]:
+        """Gather information that could be useful for a tool generating
+        user-facing documentation.
+
+        Use :meth:`click.Context.to_info_dict` to traverse the entire
+        CLI structure.
+
+        .. versionadded:: 8.0
+        """
+        return {
+            "name": self.name,
+            "param_type_name": self.param_type_name,
+            "opts": self.opts,
+            "secondary_opts": self.secondary_opts,
+            "type": self.type.to_info_dict(),
+            "required": self.required,
+            "nargs": self.nargs,
+            "multiple": self.multiple,
+            "default": self.default,
+            "envvar": self.envvar,
+        }
+
+    def __repr__(self) -> str:
+        return f"<{self.__class__.__name__} {self.name}>"
+
+    def _parse_decls(
+        self, decls: t.Sequence[str], expose_value: bool
+    ) -> t.Tuple[t.Optional[str], t.List[str], t.List[str]]:
+        raise NotImplementedError()
+
+    @property
+    def human_readable_name(self) -> str:
+        """Returns the human readable name of this parameter.  This is the
+        same as the name for options, but the metavar for arguments.
+        """
+        return self.name  # type: ignore
+
+    def make_metavar(self) -> str:
+        if self.metavar is not None:
+            return self.metavar
+
+        metavar = self.type.get_metavar(self)
+
+        if metavar is None:
+            metavar = self.type.name.upper()
+
+        if self.nargs != 1:
+            metavar += "..."
+
+        return metavar
+
+    @t.overload
+    def get_default(
+        self, ctx: Context, call: "te.Literal[True]" = True
+    ) -> t.Optional[t.Any]:
+        ...
+
+    @t.overload
+    def get_default(
+        self, ctx: Context, call: bool = ...
+    ) -> t.Optional[t.Union[t.Any, t.Callable[[], t.Any]]]:
+        ...
+
+    def get_default(
+        self, ctx: Context, call: bool = True
+    ) -> t.Optional[t.Union[t.Any, t.Callable[[], t.Any]]]:
+        """Get the default for the parameter. Tries
+        :meth:`Context.lookup_default` first, then the local default.
+
+        :param ctx: Current context.
+        :param call: If the default is a callable, call it. Disable to
+            return the callable instead.
+
+        .. versionchanged:: 8.0.2
+            Type casting is no longer performed when getting a default.
+
+        .. versionchanged:: 8.0.1
+            Type casting can fail in resilient parsing mode. Invalid
+            defaults will not prevent showing help text.
+
+        .. versionchanged:: 8.0
+            Looks at ``ctx.default_map`` first.
+
+        .. versionchanged:: 8.0
+            Added the ``call`` parameter.
+        """
+        value = ctx.lookup_default(self.name, call=False)  # type: ignore
+
+        if value is None:
+            value = self.default
+
+        if call and callable(value):
+            value = value()
+
+        return value
+
+    def add_to_parser(self, parser: OptionParser, ctx: Context) -> None:
+        raise NotImplementedError()
+
+    def consume_value(
+        self, ctx: Context, opts: t.Mapping[str, t.Any]
+    ) -> t.Tuple[t.Any, ParameterSource]:
+        value = opts.get(self.name)  # type: ignore
+        source = ParameterSource.COMMANDLINE
+
+        if value is None:
+            value = self.value_from_envvar(ctx)
+            source = ParameterSource.ENVIRONMENT
+
+        if value is None:
+            value = ctx.lookup_default(self.name)  # type: ignore
+            source = ParameterSource.DEFAULT_MAP
+
+        if value is None:
+            value = self.get_default(ctx)
+            source = ParameterSource.DEFAULT
+
+        return value, source
+
+    def type_cast_value(self, ctx: Context, value: t.Any) -> t.Any:
+        """Convert and validate a value against the option's
+        :attr:`type`, :attr:`multiple`, and :attr:`nargs`.
+        """
+        if value is None:
+            return () if self.multiple or self.nargs == -1 else None
+
+        def check_iter(value: t.Any) -> t.Iterator[t.Any]:
+            try:
+                return _check_iter(value)
+            except TypeError:
+                # This should only happen when passing in args manually,
+                # the parser should construct an iterable when parsing
+                # the command line.
+                raise BadParameter(
+                    _("Value must be an iterable."), ctx=ctx, param=self
+                ) from None
+
+        if self.nargs == 1 or self.type.is_composite:
+
+            def convert(value: t.Any) -> t.Any:
+                return self.type(value, param=self, ctx=ctx)
+
+        elif self.nargs == -1:
+
+            def convert(value: t.Any) -> t.Any:  # t.Tuple[t.Any, ...]
+                return tuple(self.type(x, self, ctx) for x in check_iter(value))
+
+        else:  # nargs > 1
+
+            def convert(value: t.Any) -> t.Any:  # t.Tuple[t.Any, ...]
+                value = tuple(check_iter(value))
+
+                if len(value) != self.nargs:
+                    raise BadParameter(
+                        ngettext(
+                            "Takes {nargs} values but 1 was given.",
+                            "Takes {nargs} values but {len} were given.",
+                            len(value),
+                        ).format(nargs=self.nargs, len=len(value)),
+                        ctx=ctx,
+                        param=self,
+                    )
+
+                return tuple(self.type(x, self, ctx) for x in value)
+
+        if self.multiple:
+            return tuple(convert(x) for x in check_iter(value))
+
+        return convert(value)
+
+    def value_is_missing(self, value: t.Any) -> bool:
+        if value is None:
+            return True
+
+        if (self.nargs != 1 or self.multiple) and value == ():
+            return True
+
+        return False
+
+    def process_value(self, ctx: Context, value: t.Any) -> t.Any:
+        value = self.type_cast_value(ctx, value)
+
+        if self.required and self.value_is_missing(value):
+            raise MissingParameter(ctx=ctx, param=self)
+
+        if self.callback is not None:
+            value = self.callback(ctx, self, value)
+
+        return value
+
+    def resolve_envvar_value(self, ctx: Context) -> t.Optional[str]:
+        if self.envvar is None:
+            return None
+
+        if isinstance(self.envvar, str):
+            rv = os.environ.get(self.envvar)
+
+            if rv:
+                return rv
+        else:
+            for envvar in self.envvar:
+                rv = os.environ.get(envvar)
+
+                if rv:
+                    return rv
+
+        return None
+
+    def value_from_envvar(self, ctx: Context) -> t.Optional[t.Any]:
+        rv: t.Optional[t.Any] = self.resolve_envvar_value(ctx)
+
+        if rv is not None and self.nargs != 1:
+            rv = self.type.split_envvar_value(rv)
+
+        return rv
+
+    def handle_parse_result(
+        self, ctx: Context, opts: t.Mapping[str, t.Any], args: t.List[str]
+    ) -> t.Tuple[t.Any, t.List[str]]:
+        with augment_usage_errors(ctx, param=self):
+            value, source = self.consume_value(ctx, opts)
+            ctx.set_parameter_source(self.name, source)  # type: ignore
+
+            try:
+                value = self.process_value(ctx, value)
+            except Exception:
+                if not ctx.resilient_parsing:
+                    raise
+
+                value = None
+
+        if self.expose_value:
+            ctx.params[self.name] = value  # type: ignore
+
+        return value, args
+
+    def get_help_record(self, ctx: Context) -> t.Optional[t.Tuple[str, str]]:
+        pass
+
+    def get_usage_pieces(self, ctx: Context) -> t.List[str]:
+        return []
+
+    def get_error_hint(self, ctx: Context) -> str:
+        """Get a stringified version of the param for use in error messages to
+        indicate which param caused the error.
+        """
+        hint_list = self.opts or [self.human_readable_name]
+        return " / ".join(f"'{x}'" for x in hint_list)
+
+    def shell_complete(self, ctx: Context, incomplete: str) -> t.List["CompletionItem"]:
+        """Return a list of completions for the incomplete value. If a
+        ``shell_complete`` function was given during init, it is used.
+        Otherwise, the :attr:`type`
+        :meth:`~click.types.ParamType.shell_complete` function is used.
+
+        :param ctx: Invocation context for this command.
+        :param incomplete: Value being completed. May be empty.
+
+        .. versionadded:: 8.0
+        """
+        if self._custom_shell_complete is not None:
+            results = self._custom_shell_complete(ctx, self, incomplete)
+
+            if results and isinstance(results[0], str):
+                from click.shell_completion import CompletionItem
+
+                results = [CompletionItem(c) for c in results]
+
+            return t.cast(t.List["CompletionItem"], results)
+
+        return self.type.shell_complete(ctx, self, incomplete)
+
+
+class Option(Parameter):
+    """Options are usually optional values on the command line and
+    have some extra features that arguments don't have.
+
+    All other parameters are passed onwards to the parameter constructor.
+
+    :param show_default: Show the default value for this option in its
+        help text. Values are not shown by default, unless
+        :attr:`Context.show_default` is ``True``. If this value is a
+        string, it shows that string in parentheses instead of the
+        actual value. This is particularly useful for dynamic options.
+        For single option boolean flags, the default remains hidden if
+        its value is ``False``.
+    :param show_envvar: Controls if an environment variable should be
+        shown on the help page. Normally, environment variables are not
+        shown.
+    :param prompt: If set to ``True`` or a non empty string then the
+        user will be prompted for input. If set to ``True`` the prompt
+        will be the option name capitalized.
+    :param confirmation_prompt: Prompt a second time to confirm the
+        value if it was prompted for. Can be set to a string instead of
+        ``True`` to customize the message.
+    :param prompt_required: If set to ``False``, the user will be
+        prompted for input only when the option was specified as a flag
+        without a value.
+    :param hide_input: If this is ``True`` then the input on the prompt
+        will be hidden from the user. This is useful for password input.
+    :param is_flag: forces this option to act as a flag.  The default is
+                    auto detection.
+    :param flag_value: which value should be used for this flag if it's
+                       enabled.  This is set to a boolean automatically if
+                       the option string contains a slash to mark two options.
+    :param multiple: if this is set to `True` then the argument is accepted
+                     multiple times and recorded.  This is similar to ``nargs``
+                     in how it works but supports arbitrary number of
+                     arguments.
+    :param count: this flag makes an option increment an integer.
+    :param allow_from_autoenv: if this is enabled then the value of this
+                               parameter will be pulled from an environment
+                               variable in case a prefix is defined on the
+                               context.
+    :param help: the help string.
+    :param hidden: hide this option from help outputs.
+    :param attrs: Other command arguments described in :class:`Parameter`.
+
+    .. versionchanged:: 8.1.0
+        Help text indentation is cleaned here instead of only in the
+        ``@option`` decorator.
+
+    .. versionchanged:: 8.1.0
+        The ``show_default`` parameter overrides
+        ``Context.show_default``.
+
+    .. versionchanged:: 8.1.0
+        The default of a single option boolean flag is not shown if the
+        default value is ``False``.
+
+    .. versionchanged:: 8.0.1
+        ``type`` is detected from ``flag_value`` if given.
+    """
+
+    param_type_name = "option"
+
+    def __init__(
+        self,
+        param_decls: t.Optional[t.Sequence[str]] = None,
+        show_default: t.Union[bool, str, None] = None,
+        prompt: t.Union[bool, str] = False,
+        confirmation_prompt: t.Union[bool, str] = False,
+        prompt_required: bool = True,
+        hide_input: bool = False,
+        is_flag: t.Optional[bool] = None,
+        flag_value: t.Optional[t.Any] = None,
+        multiple: bool = False,
+        count: bool = False,
+        allow_from_autoenv: bool = True,
+        type: t.Optional[t.Union[types.ParamType, t.Any]] = None,
+        help: t.Optional[str] = None,
+        hidden: bool = False,
+        show_choices: bool = True,
+        show_envvar: bool = False,
+        **attrs: t.Any,
+    ) -> None:
+        if help:
+            help = inspect.cleandoc(help)
+
+        default_is_missing = "default" not in attrs
+        super().__init__(param_decls, type=type, multiple=multiple, **attrs)
+
+        if prompt is True:
+            if self.name is None:
+                raise TypeError("'name' is required with 'prompt=True'.")
+
+            prompt_text: t.Optional[str] = self.name.replace("_", " ").capitalize()
+        elif prompt is False:
+            prompt_text = None
+        else:
+            prompt_text = prompt
+
+        self.prompt = prompt_text
+        self.confirmation_prompt = confirmation_prompt
+        self.prompt_required = prompt_required
+        self.hide_input = hide_input
+        self.hidden = hidden
+
+        # If prompt is enabled but not required, then the option can be
+        # used as a flag to indicate using prompt or flag_value.
+        self._flag_needs_value = self.prompt is not None and not self.prompt_required
+
+        if is_flag is None:
+            if flag_value is not None:
+                # Implicitly a flag because flag_value was set.
+                is_flag = True
+            elif self._flag_needs_value:
+                # Not a flag, but when used as a flag it shows a prompt.
+                is_flag = False
+            else:
+                # Implicitly a flag because flag options were given.
+                is_flag = bool(self.secondary_opts)
+        elif is_flag is False and not self._flag_needs_value:
+            # Not a flag, and prompt is not enabled, can be used as a
+            # flag if flag_value is set.
+            self._flag_needs_value = flag_value is not None
+
+        self.default: t.Union[t.Any, t.Callable[[], t.Any]]
+
+        if is_flag and default_is_missing and not self.required:
+            if multiple:
+                self.default = ()
+            else:
+                self.default = False
+
+        if flag_value is None:
+            flag_value = not self.default
+
+        self.type: types.ParamType
+        if is_flag and type is None:
+            # Re-guess the type from the flag value instead of the
+            # default.
+            self.type = types.convert_type(None, flag_value)
+
+        self.is_flag: bool = is_flag
+        self.is_bool_flag: bool = is_flag and isinstance(self.type, types.BoolParamType)
+        self.flag_value: t.Any = flag_value
+
+        # Counting
+        self.count = count
+        if count:
+            if type is None:
+                self.type = types.IntRange(min=0)
+            if default_is_missing:
+                self.default = 0
+
+        self.allow_from_autoenv = allow_from_autoenv
+        self.help = help
+        self.show_default = show_default
+        self.show_choices = show_choices
+        self.show_envvar = show_envvar
+
+        if __debug__:
+            if self.nargs == -1:
+                raise TypeError("nargs=-1 is not supported for options.")
+
+            if self.prompt and self.is_flag and not self.is_bool_flag:
+                raise TypeError("'prompt' is not valid for non-boolean flag.")
+
+            if not self.is_bool_flag and self.secondary_opts:
+                raise TypeError("Secondary flag is not valid for non-boolean flag.")
+
+            if self.is_bool_flag and self.hide_input and self.prompt is not None:
+                raise TypeError(
+                    "'prompt' with 'hide_input' is not valid for boolean flag."
+                )
+
+            if self.count:
+                if self.multiple:
+                    raise TypeError("'count' is not valid with 'multiple'.")
+
+                if self.is_flag:
+                    raise TypeError("'count' is not valid with 'is_flag'.")
+
+    def to_info_dict(self) -> t.Dict[str, t.Any]:
+        info_dict = super().to_info_dict()
+        info_dict.update(
+            help=self.help,
+            prompt=self.prompt,
+            is_flag=self.is_flag,
+            flag_value=self.flag_value,
+            count=self.count,
+            hidden=self.hidden,
+        )
+        return info_dict
+
+    def _parse_decls(
+        self, decls: t.Sequence[str], expose_value: bool
+    ) -> t.Tuple[t.Optional[str], t.List[str], t.List[str]]:
+        opts = []
+        secondary_opts = []
+        name = None
+        possible_names = []
+
+        for decl in decls:
+            if decl.isidentifier():
+                if name is not None:
+                    raise TypeError(f"Name '{name}' defined twice")
+                name = decl
+            else:
+                split_char = ";" if decl[:1] == "/" else "/"
+                if split_char in decl:
+                    first, second = decl.split(split_char, 1)
+                    first = first.rstrip()
+                    if first:
+                        possible_names.append(split_opt(first))
+                        opts.append(first)
+                    second = second.lstrip()
+                    if second:
+                        secondary_opts.append(second.lstrip())
+                    if first == second:
+                        raise ValueError(
+                            f"Boolean option {decl!r} cannot use the"
+                            " same flag for true/false."
+                        )
+                else:
+                    possible_names.append(split_opt(decl))
+                    opts.append(decl)
+
+        if name is None and possible_names:
+            possible_names.sort(key=lambda x: -len(x[0]))  # group long options first
+            name = possible_names[0][1].replace("-", "_").lower()
+            if not name.isidentifier():
+                name = None
+
+        if name is None:
+            if not expose_value:
+                return None, opts, secondary_opts
+            raise TypeError("Could not determine name for option")
+
+        if not opts and not secondary_opts:
+            raise TypeError(
+                f"No options defined but a name was passed ({name})."
+                " Did you mean to declare an argument instead? Did"
+                f" you mean to pass '--{name}'?"
+            )
+
+        return name, opts, secondary_opts
+
+    def add_to_parser(self, parser: OptionParser, ctx: Context) -> None:
+        if self.multiple:
+            action = "append"
+        elif self.count:
+            action = "count"
+        else:
+            action = "store"
+
+        if self.is_flag:
+            action = f"{action}_const"
+
+            if self.is_bool_flag and self.secondary_opts:
+                parser.add_option(
+                    obj=self, opts=self.opts, dest=self.name, action=action, const=True
+                )
+                parser.add_option(
+                    obj=self,
+                    opts=self.secondary_opts,
+                    dest=self.name,
+                    action=action,
+                    const=False,
+                )
+            else:
+                parser.add_option(
+                    obj=self,
+                    opts=self.opts,
+                    dest=self.name,
+                    action=action,
+                    const=self.flag_value,
+                )
+        else:
+            parser.add_option(
+                obj=self,
+                opts=self.opts,
+                dest=self.name,
+                action=action,
+                nargs=self.nargs,
+            )
+
+    def get_help_record(self, ctx: Context) -> t.Optional[t.Tuple[str, str]]:
+        if self.hidden:
+            return None
+
+        any_prefix_is_slash = False
+
+        def _write_opts(opts: t.Sequence[str]) -> str:
+            nonlocal any_prefix_is_slash
+
+            rv, any_slashes = join_options(opts)
+
+            if any_slashes:
+                any_prefix_is_slash = True
+
+            if not self.is_flag and not self.count:
+                rv += f" {self.make_metavar()}"
+
+            return rv
+
+        rv = [_write_opts(self.opts)]
+
+        if self.secondary_opts:
+            rv.append(_write_opts(self.secondary_opts))
+
+        help = self.help or ""
+        extra = []
+
+        if self.show_envvar:
+            envvar = self.envvar
+
+            if envvar is None:
+                if (
+                    self.allow_from_autoenv
+                    and ctx.auto_envvar_prefix is not None
+                    and self.name is not None
+                ):
+                    envvar = f"{ctx.auto_envvar_prefix}_{self.name.upper()}"
+
+            if envvar is not None:
+                var_str = (
+                    envvar
+                    if isinstance(envvar, str)
+                    else ", ".join(str(d) for d in envvar)
+                )
+                extra.append(_("env var: {var}").format(var=var_str))
+
+        # Temporarily enable resilient parsing to avoid type casting
+        # failing for the default. Might be possible to extend this to
+        # help formatting in general.
+        resilient = ctx.resilient_parsing
+        ctx.resilient_parsing = True
+
+        try:
+            default_value = self.get_default(ctx, call=False)
+        finally:
+            ctx.resilient_parsing = resilient
+
+        show_default = False
+        show_default_is_str = False
+
+        if self.show_default is not None:
+            if isinstance(self.show_default, str):
+                show_default_is_str = show_default = True
+            else:
+                show_default = self.show_default
+        elif ctx.show_default is not None:
+            show_default = ctx.show_default
+
+        if show_default_is_str or (show_default and (default_value is not None)):
+            if show_default_is_str:
+                default_string = f"({self.show_default})"
+            elif isinstance(default_value, (list, tuple)):
+                default_string = ", ".join(str(d) for d in default_value)
+            elif inspect.isfunction(default_value):
+                default_string = _("(dynamic)")
+            elif self.is_bool_flag and self.secondary_opts:
+                # For boolean flags that have distinct True/False opts,
+                # use the opt without prefix instead of the value.
+                default_string = split_opt(
+                    (self.opts if self.default else self.secondary_opts)[0]
+                )[1]
+            elif self.is_bool_flag and not self.secondary_opts and not default_value:
+                default_string = ""
+            else:
+                default_string = str(default_value)
+
+            if default_string:
+                extra.append(_("default: {default}").format(default=default_string))
+
+        if (
+            isinstance(self.type, types._NumberRangeBase)
+            # skip count with default range type
+            and not (self.count and self.type.min == 0 and self.type.max is None)
+        ):
+            range_str = self.type._describe_range()
+
+            if range_str:
+                extra.append(range_str)
+
+        if self.required:
+            extra.append(_("required"))
+
+        if extra:
+            extra_str = "; ".join(extra)
+            help = f"{help}  [{extra_str}]" if help else f"[{extra_str}]"
+
+        return ("; " if any_prefix_is_slash else " / ").join(rv), help
+
+    @t.overload
+    def get_default(
+        self, ctx: Context, call: "te.Literal[True]" = True
+    ) -> t.Optional[t.Any]:
+        ...
+
+    @t.overload
+    def get_default(
+        self, ctx: Context, call: bool = ...
+    ) -> t.Optional[t.Union[t.Any, t.Callable[[], t.Any]]]:
+        ...
+
+    def get_default(
+        self, ctx: Context, call: bool = True
+    ) -> t.Optional[t.Union[t.Any, t.Callable[[], t.Any]]]:
+        # If we're a non boolean flag our default is more complex because
+        # we need to look at all flags in the same group to figure out
+        # if we're the default one in which case we return the flag
+        # value as default.
+        if self.is_flag and not self.is_bool_flag:
+            for param in ctx.command.params:
+                if param.name == self.name and param.default:
+                    return t.cast(Option, param).flag_value
+
+            return None
+
+        return super().get_default(ctx, call=call)
+
+    def prompt_for_value(self, ctx: Context) -> t.Any:
+        """This is an alternative flow that can be activated in the full
+        value processing if a value does not exist.  It will prompt the
+        user until a valid value exists and then returns the processed
+        value as result.
+        """
+        assert self.prompt is not None
+
+        # Calculate the default before prompting anything to be stable.
+        default = self.get_default(ctx)
+
+        # If this is a prompt for a flag we need to handle this
+        # differently.
+        if self.is_bool_flag:
+            return confirm(self.prompt, default)
+
+        return prompt(
+            self.prompt,
+            default=default,
+            type=self.type,
+            hide_input=self.hide_input,
+            show_choices=self.show_choices,
+            confirmation_prompt=self.confirmation_prompt,
+            value_proc=lambda x: self.process_value(ctx, x),
+        )
+
+    def resolve_envvar_value(self, ctx: Context) -> t.Optional[str]:
+        rv = super().resolve_envvar_value(ctx)
+
+        if rv is not None:
+            return rv
+
+        if (
+            self.allow_from_autoenv
+            and ctx.auto_envvar_prefix is not None
+            and self.name is not None
+        ):
+            envvar = f"{ctx.auto_envvar_prefix}_{self.name.upper()}"
+            rv = os.environ.get(envvar)
+
+            if rv:
+                return rv
+
+        return None
+
+    def value_from_envvar(self, ctx: Context) -> t.Optional[t.Any]:
+        rv: t.Optional[t.Any] = self.resolve_envvar_value(ctx)
+
+        if rv is None:
+            return None
+
+        value_depth = (self.nargs != 1) + bool(self.multiple)
+
+        if value_depth > 0:
+            rv = self.type.split_envvar_value(rv)
+
+            if self.multiple and self.nargs != 1:
+                rv = batch(rv, self.nargs)
+
+        return rv
+
+    def consume_value(
+        self, ctx: Context, opts: t.Mapping[str, "Parameter"]
+    ) -> t.Tuple[t.Any, ParameterSource]:
+        value, source = super().consume_value(ctx, opts)
+
+        # The parser will emit a sentinel value if the option can be
+        # given as a flag without a value. This is different from None
+        # to distinguish from the flag not being given at all.
+        if value is _flag_needs_value:
+            if self.prompt is not None and not ctx.resilient_parsing:
+                value = self.prompt_for_value(ctx)
+                source = ParameterSource.PROMPT
+            else:
+                value = self.flag_value
+                source = ParameterSource.COMMANDLINE
+
+        elif (
+            self.multiple
+            and value is not None
+            and any(v is _flag_needs_value for v in value)
+        ):
+            value = [self.flag_value if v is _flag_needs_value else v for v in value]
+            source = ParameterSource.COMMANDLINE
+
+        # The value wasn't set, or used the param's default, prompt if
+        # prompting is enabled.
+        elif (
+            source in {None, ParameterSource.DEFAULT}
+            and self.prompt is not None
+            and (self.required or self.prompt_required)
+            and not ctx.resilient_parsing
+        ):
+            value = self.prompt_for_value(ctx)
+            source = ParameterSource.PROMPT
+
+        return value, source
+
+
+class Argument(Parameter):
+    """Arguments are positional parameters to a command.  They generally
+    provide fewer features than options but can have infinite ``nargs``
+    and are required by default.
+
+    All parameters are passed onwards to the constructor of :class:`Parameter`.
+    """
+
+    param_type_name = "argument"
+
+    def __init__(
+        self,
+        param_decls: t.Sequence[str],
+        required: t.Optional[bool] = None,
+        **attrs: t.Any,
+    ) -> None:
+        if required is None:
+            if attrs.get("default") is not None:
+                required = False
+            else:
+                required = attrs.get("nargs", 1) > 0
+
+        if "multiple" in attrs:
+            raise TypeError("__init__() got an unexpected keyword argument 'multiple'.")
+
+        super().__init__(param_decls, required=required, **attrs)
+
+        if __debug__:
+            if self.default is not None and self.nargs == -1:
+                raise TypeError("'default' is not supported for nargs=-1.")
+
+    @property
+    def human_readable_name(self) -> str:
+        if self.metavar is not None:
+            return self.metavar
+        return self.name.upper()  # type: ignore
+
+    def make_metavar(self) -> str:
+        if self.metavar is not None:
+            return self.metavar
+        var = self.type.get_metavar(self)
+        if not var:
+            var = self.name.upper()  # type: ignore
+        if not self.required:
+            var = f"[{var}]"
+        if self.nargs != 1:
+            var += "..."
+        return var
+
+    def _parse_decls(
+        self, decls: t.Sequence[str], expose_value: bool
+    ) -> t.Tuple[t.Optional[str], t.List[str], t.List[str]]:
+        if not decls:
+            if not expose_value:
+                return None, [], []
+            raise TypeError("Could not determine name for argument")
+        if len(decls) == 1:
+            name = arg = decls[0]
+            name = name.replace("-", "_").lower()
+        else:
+            raise TypeError(
+                "Arguments take exactly one parameter declaration, got"
+                f" {len(decls)}."
+            )
+        return name, [arg], []
+
+    def get_usage_pieces(self, ctx: Context) -> t.List[str]:
+        return [self.make_metavar()]
+
+    def get_error_hint(self, ctx: Context) -> str:
+        return f"'{self.make_metavar()}'"
+
+    def add_to_parser(self, parser: OptionParser, ctx: Context) -> None:
+        parser.add_argument(dest=self.name, nargs=self.nargs, obj=self)