path: root/sphinx/util/inspect.py

"""Helpers for inspecting Python modules.
"""

import builtins
import contextlib
import enum
import inspect
import re
import sys
import types
import typing
import warnings
from functools import partial, partialmethod
from importlib import import_module
from inspect import Parameter, isclass, ismethod, ismethoddescriptor, ismodule  # NOQA
from io import StringIO
from types import ModuleType
from typing import Any, Callable, Dict, Mapping, Optional, Sequence, Tuple, Type, cast

from sphinx.deprecation import RemovedInSphinx50Warning
from sphinx.pycode.ast import ast  # for py36-37
from sphinx.pycode.ast import unparse as ast_unparse
from sphinx.util import logging
from sphinx.util.typing import ForwardRef
from sphinx.util.typing import stringify as stringify_annotation

if sys.version_info > (3, 7):
    from types import ClassMethodDescriptorType, MethodDescriptorType, WrapperDescriptorType
else:
    ClassMethodDescriptorType = type(object.__init__)
    MethodDescriptorType = type(str.join)
    WrapperDescriptorType = type(dict.__dict__['fromkeys'])

if False:
    # For type annotation
    from typing import Type  # NOQA

logger = logging.getLogger(__name__)

memory_address_re = re.compile(r' at 0x[0-9a-f]{8,16}(?=>)', re.IGNORECASE)


# Copied from the definition of inspect.getfullargspec from Python master,
# and modified to remove the use of special flags that break decorated
# callables and bound methods in the name of backwards compatibility. Used
# under the terms of PSF license v2, which requires the above statement
# and the following:
#
#   Copyright (c) 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
#   2010, 2011, 2012, 2013, 2014, 2015, 2016, 2017 Python Software
#   Foundation; All Rights Reserved
def getargspec(func: Callable) -> Any:
    """Like inspect.getfullargspec but supports bound methods, and wrapped
    methods."""
    warnings.warn('sphinx.ext.inspect.getargspec() is deprecated',
                  RemovedInSphinx50Warning, stacklevel=2)

    sig = inspect.signature(func)

    args = []
    varargs = None
    varkw = None
    kwonlyargs = []
    defaults = ()
    annotations = {}
    defaults = ()
    kwdefaults = {}

    if sig.return_annotation is not sig.empty:
        annotations['return'] = sig.return_annotation

    for param in sig.parameters.values():
        kind = param.kind
        name = param.name

        if kind is Parameter.POSITIONAL_ONLY:
            args.append(name)
        elif kind is Parameter.POSITIONAL_OR_KEYWORD:
            args.append(name)
            if param.default is not param.empty:
                defaults += (param.default,)  # type: ignore
        elif kind is Parameter.VAR_POSITIONAL:
            varargs = name
        elif kind is Parameter.KEYWORD_ONLY:
            kwonlyargs.append(name)
            if param.default is not param.empty:
                kwdefaults[name] = param.default
        elif kind is Parameter.VAR_KEYWORD:
            varkw = name

        if param.annotation is not param.empty:
            annotations[name] = param.annotation

    if not kwdefaults:
        # compatibility with 'func.__kwdefaults__'
        kwdefaults = None

    if not defaults:
        # compatibility with 'func.__defaults__'
        defaults = None

    return inspect.FullArgSpec(args, varargs, varkw, defaults,
                               kwonlyargs, kwdefaults, annotations)


def unwrap(obj: Any) -> Any:
    """Get an original object from wrapped object (wrapped functions)."""
    try:
        if hasattr(obj, '__sphinx_mock__'):
            # Skip unwrapping mock object to avoid RecursionError
            return obj
        else:
            return inspect.unwrap(obj)
    except ValueError:
        # might be a mock object
        return obj


def unwrap_all(obj: Any, *, stop: Callable = None) -> Any:
    """
    Get an original object from wrapped object (unwrapping partials, wrapped
    functions, and other decorators).
    """
    while True:
        if stop and stop(obj):
            return obj
        elif ispartial(obj):
            obj = obj.func
        elif inspect.isroutine(obj) and hasattr(obj, '__wrapped__'):
            obj = obj.__wrapped__  # type: ignore
        elif isclassmethod(obj):
            obj = obj.__func__
        elif isstaticmethod(obj):
            obj = obj.__func__
        else:
            return obj


def getall(obj: Any) -> Optional[Sequence[str]]:
    """Get __all__ attribute of the module as dict.

    Return None if given *obj* does not have __all__.
    Raises ValueError if given *obj* have invalid __all__.
    """
    __all__ = safe_getattr(obj, '__all__', None)
    if __all__ is None:
        return None
    else:
        if (isinstance(__all__, (list, tuple)) and all(isinstance(e, str) for e in __all__)):
            return __all__
        else:
            raise ValueError(__all__)


def getannotations(obj: Any) -> Mapping[str, Any]:
    """Get __annotations__ from given *obj* safely."""
    __annotations__ = safe_getattr(obj, '__annotations__', None)
    if isinstance(__annotations__, Mapping):
        return __annotations__
    else:
        return {}


def getglobals(obj: Any) -> Mapping[str, Any]:
    """Get __globals__ from given *obj* safely."""
    __globals__ = safe_getattr(obj, '__globals__', None)
    if isinstance(__globals__, Mapping):
        return __globals__
    else:
        return {}


def getmro(obj: Any) -> Tuple[Type, ...]:
    """Get __mro__ from given *obj* safely."""
    __mro__ = safe_getattr(obj, '__mro__', None)
    if isinstance(__mro__, tuple):
        return __mro__
    else:
        return tuple()


def getorigbases(obj: Any) -> Optional[Tuple[Any, ...]]:
    """Get __orig_bases__ from *obj* safely."""
    if not inspect.isclass(obj):
        return None

    # Get __orig_bases__ from obj.__dict__ to avoid accessing the parent's __orig_bases__.
    # refs: https://github.com/sphinx-doc/sphinx/issues/9607
    __dict__ = safe_getattr(obj, '__dict__', {})
    __orig_bases__ = __dict__.get('__orig_bases__')
    if isinstance(__orig_bases__, tuple) and len(__orig_bases__) > 0:
        return __orig_bases__
    else:
        return None


def getslots(obj: Any) -> Optional[Dict]:
    """Get __slots__ attribute of the class as dict.

    Return None if gienv *obj* does not have __slots__.
    Raises TypeError if given *obj* is not a class.
    Raises ValueError if given *obj* have invalid __slots__.
    """
    if not inspect.isclass(obj):
        raise TypeError

    __slots__ = safe_getattr(obj, '__slots__', None)
    if __slots__ is None:
        return None
    elif isinstance(__slots__, dict):
        return __slots__
    elif isinstance(__slots__, str):
        return {__slots__: None}
    elif isinstance(__slots__, (list, tuple)):
        return {e: None for e in __slots__}
    else:
        raise ValueError


def isNewType(obj: Any) -> bool:
    """Check the if object is a kind of NewType."""
    if sys.version_info >= (3, 10):
        return isinstance(obj, typing.NewType)
    else:
        __module__ = safe_getattr(obj, '__module__', None)
        __qualname__ = safe_getattr(obj, '__qualname__', None)
        if __module__ == 'typing' and __qualname__ == 'NewType.<locals>.new_type':
            return True
        else:
            return False


def isenumclass(x: Any) -> bool:
    """Check if the object is subclass of enum."""
    return inspect.isclass(x) and issubclass(x, enum.Enum)


def isenumattribute(x: Any) -> bool:
    """Check if the object is attribute of enum."""
    return isinstance(x, enum.Enum)


def unpartial(obj: Any) -> Any:
    """Get an original object from partial object.

    This returns given object itself if not partial.
    """
    while ispartial(obj):
        obj = obj.func

    return obj


def ispartial(obj: Any) -> bool:
    """Check if the object is partial."""
    return isinstance(obj, (partial, partialmethod))


def isclassmethod(obj: Any, cls: Any = None, name: str = None) -> bool:
    """Check if the object is classmethod."""
    if isinstance(obj, classmethod):
        return True
    elif inspect.ismethod(obj) and obj.__self__ is not None and isclass(obj.__self__):
        return True
    elif cls and name:
        placeholder = object()
        for basecls in getmro(cls):
            meth = basecls.__dict__.get(name, placeholder)
            if meth is not placeholder:
                return isclassmethod(meth)

    return False


def isstaticmethod(obj: Any, cls: Any = None, name: str = None) -> bool:
    """Check if the object is staticmethod."""
    if isinstance(obj, staticmethod):
        return True
    elif cls and name:
        # trace __mro__ if the method is defined in parent class
        #
        # .. note:: This only works well with new style classes.
        for basecls in getattr(cls, '__mro__', [cls]):
            meth = basecls.__dict__.get(name)
            if meth:
                if isinstance(meth, staticmethod):
                    return True
                else:
                    return False

    return False


def isdescriptor(x: Any) -> bool:
    """Check if the object is some kind of descriptor."""
    for item in '__get__', '__set__', '__delete__':
        if callable(safe_getattr(x, item, None)):
            return True
    return False


def isabstractmethod(obj: Any) -> bool:
    """Check if the object is an abstractmethod."""
    return safe_getattr(obj, '__isabstractmethod__', False) is True


def is_cython_function_or_method(obj: Any) -> bool:
    """Check if the object is a function or method in cython."""
    try:
        return obj.__class__.__name__ == 'cython_function_or_method'
    except AttributeError:
        return False


def isattributedescriptor(obj: Any) -> bool:
    """Check if the object is an attribute like descriptor."""
    if inspect.isdatadescriptor(obj):
        # data descriptor is kind of attribute
        return True
    elif isdescriptor(obj):
        # non data descriptor
        unwrapped = unwrap(obj)
        if isfunction(unwrapped) or isbuiltin(unwrapped) or inspect.ismethod(unwrapped):
            # attribute must not be either function, builtin and method
            return False
        elif is_cython_function_or_method(unwrapped):
            # attribute must not be either function and method (for cython)
            return False
        elif inspect.isclass(unwrapped):
            # attribute must not be a class
            return False
        elif isinstance(unwrapped, (ClassMethodDescriptorType,
                                    MethodDescriptorType,
                                    WrapperDescriptorType)):
            # attribute must not be a method descriptor
            return False
        elif type(unwrapped).__name__ == "instancemethod":
            # attribute must not be an instancemethod (C-API)
            return False
        else:
            return True
    else:
        return False


def is_singledispatch_function(obj: Any) -> bool:
    """Check if the object is singledispatch function."""
    if (inspect.isfunction(obj) and
            hasattr(obj, 'dispatch') and
            hasattr(obj, 'register') and
            obj.dispatch.__module__ == 'functools'):  # type: ignore
        return True
    else:
        return False


def is_singledispatch_method(obj: Any) -> bool:
    """Check if the object is singledispatch method."""
    try:
        from functools import singledispatchmethod  # type: ignore
        return isinstance(obj, singledispatchmethod)
    except ImportError:  # py36-37
        return False


def isfunction(obj: Any) -> bool:
    """Check if the object is function."""
    return inspect.isfunction(unwrap_all(obj))


def isbuiltin(obj: Any) -> bool:
    """Check if the object is builtin."""
    return inspect.isbuiltin(unwrap_all(obj))


def isroutine(obj: Any) -> bool:
    """Check is any kind of function or method."""
    return inspect.isroutine(unwrap_all(obj))


def iscoroutinefunction(obj: Any) -> bool:
    """Check if the object is coroutine-function."""
    def iswrappedcoroutine(obj: Any) -> bool:
        """Check if the object is wrapped coroutine-function."""
        if isstaticmethod(obj) or isclassmethod(obj) or ispartial(obj):
            # staticmethod, classmethod and partial method are not a wrapped coroutine-function
            # Note: Since 3.10, staticmethod and classmethod becomes a kind of wrappers
            return False
        elif hasattr(obj, '__wrapped__'):
            return True
        else:
            return False

    obj = unwrap_all(obj, stop=iswrappedcoroutine)
    if hasattr(obj, '__code__') and inspect.iscoroutinefunction(obj):
        # check obj.__code__ because iscoroutinefunction() crashes for custom method-like
        # objects (see https://github.com/sphinx-doc/sphinx/issues/6605)
        return True
    else:
        return False


def isasyncgenfunction(obj: Any) -> bool:
    """Check if the object is async-gen function."""
    if hasattr(obj, '__code__') and inspect.isasyncgenfunction(obj):
        # check obj.__code__ because isasyncgenfunction() crashes for custom method-like
        # objects on python3.7 (see https://github.com/sphinx-doc/sphinx/issues/9838)
        return True
    else:
        return False


def isproperty(obj: Any) -> bool:
    """Check if the object is property."""
    if sys.version_info >= (3, 8):
        from functools import cached_property  # cached_property is available since py3.8
        if isinstance(obj, cached_property):
            return True

    return isinstance(obj, property)


def isgenericalias(obj: Any) -> bool:
    """Check if the object is GenericAlias."""
    if (hasattr(typing, '_GenericAlias') and  # only for py37+
            isinstance(obj, typing._GenericAlias)):  # type: ignore
        return True
    elif (hasattr(types, 'GenericAlias') and  # only for py39+
          isinstance(obj, types.GenericAlias)):  # type: ignore
        return True
    elif (hasattr(typing, '_SpecialGenericAlias') and  # for py39+
            isinstance(obj, typing._SpecialGenericAlias)):  # type: ignore
        return True
    else:
        return False


def safe_getattr(obj: Any, name: str, *defargs: Any) -> Any:
    """A getattr() that turns all exceptions into AttributeErrors."""
    try:
        return getattr(obj, name, *defargs)
    except Exception as exc:
        # sometimes accessing a property raises an exception (e.g.
        # NotImplementedError), so let's try to read the attribute directly
        try:
            # In case the object does weird things with attribute access
            # such that accessing `obj.__dict__` may raise an exception
            return obj.__dict__[name]
        except Exception:
            pass

        # this is a catch-all for all the weird things that some modules do
        # with attribute access
        if defargs:
            return defargs[0]

        raise AttributeError(name) from exc


def object_description(object: Any) -> str:
    """A repr() implementation that returns text safe to use in reST context."""
    if isinstance(object, dict):
        try:
            sorted_keys = sorted(object)
        except Exception:
            pass  # Cannot sort dict keys, fall back to generic repr
        else:
            items = ("%s: %s" %
                     (object_description(key), object_description(object[key]))
                     for key in sorted_keys)
            return "{%s}" % ", ".join(items)
    elif isinstance(object, set):
        try:
            sorted_values = sorted(object)
        except TypeError:
            pass  # Cannot sort set values, fall back to generic repr
        else:
            return "{%s}" % ", ".join(object_description(x) for x in sorted_values)
    elif isinstance(object, frozenset):
        try:
            sorted_values = sorted(object)
        except TypeError:
            pass  # Cannot sort frozenset values, fall back to generic repr
        else:
            return "frozenset({%s})" % ", ".join(object_description(x)
                                                 for x in sorted_values)
    elif isinstance(object, enum.Enum):
        return "%s.%s" % (object.__class__.__name__, object.name)

    try:
        s = repr(object)
    except Exception as exc:
        raise ValueError from exc
    # Strip non-deterministic memory addresses such as
    # ``<__main__.A at 0x7f68cb685710>``
    s = memory_address_re.sub('', s)
    return s.replace('\n', ' ')


def is_builtin_class_method(obj: Any, attr_name: str) -> bool:
    """If attr_name is implemented at builtin class, return True.

        >>> is_builtin_class_method(int, '__init__')
        True

    Why this function needed? CPython implements int.__init__ by Descriptor
    but PyPy implements it by pure Python code.
    """
    try:
        mro = getmro(obj)
        cls = next(c for c in mro if attr_name in safe_getattr(c, '__dict__', {}))
    except StopIteration:
        return False

    try:
        name = safe_getattr(cls, '__name__')
    except AttributeError:
        return False

    return getattr(builtins, name, None) is cls


class DefaultValue:
    """A simple wrapper for default value of the parameters of overload functions."""

    def __init__(self, value: str) -> None:
        self.value = value

    def __eq__(self, other: object) -> bool:
        return self.value == other

    def __repr__(self) -> str:
        return self.value


class TypeAliasForwardRef:
    """Pseudo typing class for autodoc_type_aliases.

    This avoids the error on evaluating the type inside `get_type_hints()`.
    """
    def __init__(self, name: str) -> None:
        self.name = name

    def __call__(self) -> None:
        # Dummy method to imitate special typing classes
        pass

    def __eq__(self, other: Any) -> bool:
        return self.name == other


class TypeAliasModule:
    """Pseudo module class for autodoc_type_aliases."""

    def __init__(self, modname: str, mapping: Dict[str, str]) -> None:
        self.__modname = modname
        self.__mapping = mapping

        self.__module: Optional[ModuleType] = None

    def __getattr__(self, name: str) -> Any:
        fullname = '.'.join(filter(None, [self.__modname, name]))
        if fullname in self.__mapping:
            # exactly matched
            return TypeAliasForwardRef(self.__mapping[fullname])
        else:
            prefix = fullname + '.'
            nested = {k: v for k, v in self.__mapping.items() if k.startswith(prefix)}
            if nested:
                # sub modules or classes found
                return TypeAliasModule(fullname, nested)
            else:
                # no sub modules or classes found.
                try:
                    # return the real submodule if exists
                    return import_module(fullname)
                except ImportError:
                    # return the real class
                    if self.__module is None:
                        self.__module = import_module(self.__modname)

                    return getattr(self.__module, name)


class TypeAliasNamespace(Dict[str, Any]):
    """Pseudo namespace class for autodoc_type_aliases.

    This enables to look up nested modules and classes like `mod1.mod2.Class`.
    """

    def __init__(self, mapping: Dict[str, str]) -> None:
        self.__mapping = mapping

    def __getitem__(self, key: str) -> Any:
        if key in self.__mapping:
            # exactly matched
            return TypeAliasForwardRef(self.__mapping[key])
        else:
            prefix = key + '.'
            nested = {k: v for k, v in self.__mapping.items() if k.startswith(prefix)}
            if nested:
                # sub modules or classes found
                return TypeAliasModule(key, nested)
            else:
                raise KeyError


def _should_unwrap(subject: Callable) -> bool:
    """Check the function should be unwrapped on getting signature."""
    __globals__ = getglobals(subject)
    if (__globals__.get('__name__') == 'contextlib' and
            __globals__.get('__file__') == contextlib.__file__):
        # contextmanger should be unwrapped
        return True

    return False


def signature(subject: Callable, bound_method: bool = False, follow_wrapped: bool = None,
              type_aliases: Dict = {}) -> inspect.Signature:
    """Return a Signature object for the given *subject*.

    :param bound_method: Specify *subject* is a bound method or not
    :param follow_wrapped: Same as ``inspect.signature()``.
    """

    if follow_wrapped is None:
        follow_wrapped = True
    else:
        warnings.warn('The follow_wrapped argument of sphinx.util.inspect.signature() is '
                      'deprecated', RemovedInSphinx50Warning, stacklevel=2)

    try:
        try:
            if _should_unwrap(subject):
                signature = inspect.signature(subject)
            else:
                signature = inspect.signature(subject, follow_wrapped=follow_wrapped)
        except ValueError:
            # follow built-in wrappers up (ex. functools.lru_cache)
            signature = inspect.signature(subject)
        parameters = list(signature.parameters.values())
        return_annotation = signature.return_annotation
    except IndexError:
        # Until python 3.6.4, cpython has been crashed on inspection for
        # partialmethods not having any arguments.
        # https://bugs.python.org/issue33009
        if hasattr(subject, '_partialmethod'):
            parameters = []
            return_annotation = Parameter.empty
        else:
            raise

    try:
        # Resolve annotations using ``get_type_hints()`` and type_aliases.
        localns = TypeAliasNamespace(type_aliases)
        annotations = typing.get_type_hints(subject, None, localns)
        for i, param in enumerate(parameters):
            if param.name in annotations:
                annotation = annotations[param.name]
                if isinstance(annotation, TypeAliasForwardRef):
                    annotation = annotation.name
                parameters[i] = param.replace(annotation=annotation)
        if 'return' in annotations:
            if isinstance(annotations['return'], TypeAliasForwardRef):
                return_annotation = annotations['return'].name
            else:
                return_annotation = annotations['return']
    except Exception:
        # ``get_type_hints()`` does not support some kind of objects like partial,
        # ForwardRef and so on.
        pass

    if bound_method:
        if inspect.ismethod(subject):
            # ``inspect.signature()`` considers the subject is a bound method and removes
            # first argument from signature.  Therefore no skips are needed here.
            pass
        else:
            if len(parameters) > 0:
                parameters.pop(0)

    # To allow to create signature object correctly for pure python functions,
    # pass an internal parameter __validate_parameters__=False to Signature
    #
    # For example, this helps a function having a default value `inspect._empty`.
    # refs: https://github.com/sphinx-doc/sphinx/issues/7935
    return inspect.Signature(parameters, return_annotation=return_annotation,
                             __validate_parameters__=False)


def evaluate_signature(sig: inspect.Signature, globalns: Dict = None, localns: Dict = None
                       ) -> inspect.Signature:
    """Evaluate unresolved type annotations in a signature object."""
    def evaluate_forwardref(ref: ForwardRef, globalns: Dict, localns: Dict) -> Any:
        """Evaluate a forward reference."""
        if sys.version_info > (3, 9):
            return ref._evaluate(globalns, localns, frozenset())
        else:
            return ref._evaluate(globalns, localns)

    def evaluate(annotation: Any, globalns: Dict, localns: Dict) -> Any:
        """Evaluate unresolved type annotation."""
        try:
            if isinstance(annotation, str):
                ref = ForwardRef(annotation, True)
                annotation = evaluate_forwardref(ref, globalns, localns)

                if isinstance(annotation, ForwardRef):
                    annotation = evaluate_forwardref(ref, globalns, localns)
                elif isinstance(annotation, str):
                    # might be a ForwardRef'ed annotation in overloaded functions
                    ref = ForwardRef(annotation, True)
                    annotation = evaluate_forwardref(ref, globalns, localns)
        except (NameError, TypeError):
            # failed to evaluate type. skipped.
            pass

        return annotation

    if globalns is None:
        globalns = {}
    if localns is None:
        localns = globalns

    parameters = list(sig.parameters.values())
    for i, param in enumerate(parameters):
        if param.annotation:
            annotation = evaluate(param.annotation, globalns, localns)
            parameters[i] = param.replace(annotation=annotation)

    return_annotation = sig.return_annotation
    if return_annotation:
        return_annotation = evaluate(return_annotation, globalns, localns)

    return sig.replace(parameters=parameters, return_annotation=return_annotation)


def stringify_signature(sig: inspect.Signature, show_annotation: bool = True,
                        show_return_annotation: bool = True,
                        unqualified_typehints: bool = False) -> str:
    """Stringify a Signature object.

    :param show_annotation: If enabled, show annotations on the signature
    :param show_return_annotation: If enabled, show annotation of the return value
    :param unqualified_typehints: If enabled, show annotations as unqualified
                                  (ex. io.StringIO -> StringIO)
    """
    if unqualified_typehints:
        mode = 'smart'
    else:
        mode = 'fully-qualified'

    args = []
    last_kind = None
    for param in sig.parameters.values():
        if param.kind != param.POSITIONAL_ONLY and last_kind == param.POSITIONAL_ONLY:
            # PEP-570: Separator for Positional Only Parameter: /
            args.append('/')
        if param.kind == param.KEYWORD_ONLY and last_kind in (param.POSITIONAL_OR_KEYWORD,
                                                              param.POSITIONAL_ONLY,
                                                              None):
            # PEP-3102: Separator for Keyword Only Parameter: *
            args.append('*')

        arg = StringIO()
        if param.kind == param.VAR_POSITIONAL:
            arg.write('*' + param.name)
        elif param.kind == param.VAR_KEYWORD:
            arg.write('**' + param.name)
        else:
            arg.write(param.name)

        if show_annotation and param.annotation is not param.empty:
            arg.write(': ')
            arg.write(stringify_annotation(param.annotation, mode))
        if param.default is not param.empty:
            if show_annotation and param.annotation is not param.empty:
                arg.write(' = ')
            else:
                arg.write('=')
            arg.write(object_description(param.default))

        args.append(arg.getvalue())
        last_kind = param.kind

    if last_kind == Parameter.POSITIONAL_ONLY:
        # PEP-570: Separator for Positional Only Parameter: /
        args.append('/')

    if (sig.return_annotation is Parameter.empty or
            show_annotation is False or
            show_return_annotation is False):
        return '(%s)' % ', '.join(args)
    else:
        annotation = stringify_annotation(sig.return_annotation, mode)
        return '(%s) -> %s' % (', '.join(args), annotation)


def signature_from_str(signature: str) -> inspect.Signature:
    """Create a Signature object from string."""
    code = 'def func' + signature + ': pass'
    module = ast.parse(code)
    function = cast(ast.FunctionDef, module.body[0])  # type: ignore

    return signature_from_ast(function, code)


def signature_from_ast(node: ast.FunctionDef, code: str = '') -> inspect.Signature:
    """Create a Signature object from AST *node*."""
    args = node.args
    defaults = list(args.defaults)
    params = []
    if hasattr(args, "posonlyargs"):
        posonlyargs = len(args.posonlyargs)  # type: ignore
        positionals = posonlyargs + len(args.args)
    else:
        posonlyargs = 0
        positionals = len(args.args)

    for _ in range(len(defaults), positionals):
        defaults.insert(0, Parameter.empty)  # type: ignore

    if hasattr(args, "posonlyargs"):
        for i, arg in enumerate(args.posonlyargs):  # type: ignore
            if defaults[i] is Parameter.empty:
                default = Parameter.empty
            else:
                default = DefaultValue(ast_unparse(defaults[i], code))  # type: ignore

            annotation = ast_unparse(arg.annotation, code) or Parameter.empty
            params.append(Parameter(arg.arg, Parameter.POSITIONAL_ONLY,
                                    default=default, annotation=annotation))

    for i, arg in enumerate(args.args):
        if defaults[i + posonlyargs] is Parameter.empty:
            default = Parameter.empty
        else:
            default = DefaultValue(ast_unparse(defaults[i + posonlyargs], code))  # type: ignore  # NOQA

        annotation = ast_unparse(arg.annotation, code) or Parameter.empty
        params.append(Parameter(arg.arg, Parameter.POSITIONAL_OR_KEYWORD,
                                default=default, annotation=annotation))

    if args.vararg:
        annotation = ast_unparse(args.vararg.annotation, code) or Parameter.empty
        params.append(Parameter(args.vararg.arg, Parameter.VAR_POSITIONAL,
                                annotation=annotation))

    for i, arg in enumerate(args.kwonlyargs):
        default = ast_unparse(args.kw_defaults[i], code) or Parameter.empty  # type: ignore
        annotation = ast_unparse(arg.annotation, code) or Parameter.empty
        params.append(Parameter(arg.arg, Parameter.KEYWORD_ONLY, default=default,
                                annotation=annotation))

    if args.kwarg:
        annotation = ast_unparse(args.kwarg.annotation, code) or Parameter.empty
        params.append(Parameter(args.kwarg.arg, Parameter.VAR_KEYWORD,
                                annotation=annotation))

    return_annotation = ast_unparse(node.returns, code) or Parameter.empty

    return inspect.Signature(params, return_annotation=return_annotation)


def getdoc(obj: Any, attrgetter: Callable = safe_getattr,
           allow_inherited: bool = False, cls: Any = None, name: str = None) -> str:
    """Get the docstring for the object.

    This tries to obtain the docstring for some kind of objects additionally:

    * partial functions
    * inherited docstring
    * inherited decorated methods
    """
    def getdoc_internal(obj: Any, attrgetter: Callable = safe_getattr) -> Optional[str]:
        doc = attrgetter(obj, '__doc__', None)
        if isinstance(doc, str):
            return doc
        else:
            return None

    if cls and name and isclassmethod(obj, cls, name):
        for basecls in getmro(cls):
            meth = basecls.__dict__.get(name)
            if meth and hasattr(meth, '__func__'):
                doc = getdoc(meth.__func__)
                if doc is not None or not allow_inherited:
                    return doc

    doc = getdoc_internal(obj)
    if ispartial(obj) and doc == obj.__class__.__doc__:
        return getdoc(obj.func)
    elif doc is None and allow_inherited:
        if cls and name:
            # Check a docstring of the attribute or method from super classes.
            for basecls in getmro(cls):
                meth = safe_getattr(basecls, name, None)
                if meth is not None:
                    doc = getdoc_internal(meth)
                    if doc is not None:
                        break

            if doc is None:
                # retry using `inspect.getdoc()`
                for basecls in getmro(cls):
                    meth = safe_getattr(basecls, name, None)
                    if meth is not None:
                        doc = inspect.getdoc(meth)
                        if doc is not None:
                            break

        if doc is None:
            doc = inspect.getdoc(obj)

    return doc