oslo.utils/oslo_utils/reflection.py

# -*- coding: utf-8 -*-

#    Copyright (C) 2012-2013 Yahoo! Inc. All Rights Reserved.
#
#    Licensed under the Apache License, Version 2.0 (the "License"); you may
#    not use this file except in compliance with the License. You may obtain
#    a copy of the License at
#
#         http://www.apache.org/licenses/LICENSE-2.0
#
#    Unless required by applicable law or agreed to in writing, software
#    distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
#    WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
#    License for the specific language governing permissions and limitations
#    under the License.

"""
Reflection module.

.. versionadded:: 1.1
"""

import inspect
import logging
import operator
import types

try:
    _TYPE_TYPE = types.TypeType
except AttributeError:
    _TYPE_TYPE = type

# See: https://docs.python.org/2/library/__builtin__.html#module-__builtin__
# and see https://docs.python.org/2/reference/executionmodel.html (and likely
# others)...
_BUILTIN_MODULES = ('builtins', '__builtin__', '__builtins__', 'exceptions')


LOG = logging.getLogger(__name__)


Parameter = inspect.Parameter
Signature = inspect.Signature
get_signature = inspect.signature


def get_members(obj, exclude_hidden=True):
    """Yields the members of an object, filtering by hidden/not hidden.

    .. versionadded:: 2.3
    """
    for (name, value) in inspect.getmembers(obj):
        if name.startswith("_") and exclude_hidden:
            continue
        yield (name, value)


def get_member_names(obj, exclude_hidden=True):
    """Get all the member names for a object."""
    return [name for (name, _obj) in
            get_members(obj, exclude_hidden=exclude_hidden)]


def get_class_name(obj, fully_qualified=True, truncate_builtins=True):
    """Get class name for object.

    If object is a type, returns name of the type. If object is a bound
    method or a class method, returns its ``self`` object's class name.
    If object is an instance of class, returns instance's class name.
    Else, name of the type of the object is returned. If fully_qualified
    is True, returns fully qualified name of the type. For builtin types,
    just name is returned. TypeError is raised if can't get class name from
    object.
    """
    if inspect.isfunction(obj):
        raise TypeError("Can't get class name.")

    if inspect.ismethod(obj):
        obj = get_method_self(obj)
    if not isinstance(obj, type):
        obj = type(obj)
    if truncate_builtins:
        try:
            built_in = obj.__module__ in _BUILTIN_MODULES
        except AttributeError:  # nosec
            pass
        else:
            if built_in:
                return obj.__name__
    if fully_qualified and hasattr(obj, '__module__'):
        return '%s.%s' % (obj.__module__, obj.__name__)
    else:
        return obj.__name__


def get_all_class_names(obj, up_to=object,
                        fully_qualified=True, truncate_builtins=True):
    """Get class names of object parent classes.

    Iterate over all class names object is instance or subclass of,
    in order of method resolution (mro). If up_to parameter is provided,
    only name of classes that are sublcasses to that class are returned.
    """
    if not isinstance(obj, type):
        obj = type(obj)
    for cls in obj.mro():
        if issubclass(cls, up_to):
            yield get_class_name(cls,
                                 fully_qualified=fully_qualified,
                                 truncate_builtins=truncate_builtins)


def get_callable_name(function):
    """Generate a name from callable.

    Tries to do the best to guess fully qualified callable name.
    """
    method_self = get_method_self(function)
    if method_self is not None:
        # This is a bound method.
        if isinstance(method_self, type):
            # This is a bound class method.
            im_class = method_self
        else:
            im_class = type(method_self)
        try:
            parts = (im_class.__module__, function.__qualname__)
        except AttributeError:
            parts = (im_class.__module__, im_class.__name__, function.__name__)
    elif inspect.ismethod(function) or inspect.isfunction(function):
        # This could be a function, a static method, a unbound method...
        try:
            parts = (function.__module__, function.__qualname__)
        except AttributeError:
            if hasattr(function, 'im_class'):
                # This is a unbound method, which exists only in python 2.x
                im_class = function.im_class
                parts = (im_class.__module__,
                         im_class.__name__, function.__name__)
            else:
                parts = (function.__module__, function.__name__)
    else:
        im_class = type(function)
        if im_class is _TYPE_TYPE:
            im_class = function
        try:
            parts = (im_class.__module__, im_class.__qualname__)
        except AttributeError:
            parts = (im_class.__module__, im_class.__name__)
    return '.'.join(parts)


def get_method_self(method):
    """Gets the ``self`` object attached to this method (or none)."""
    if not inspect.ismethod(method):
        return None
    try:
        return operator.attrgetter("__self__")(method)
    except AttributeError:
        return None


def is_same_callback(callback1, callback2, strict=True):
    """Returns if the two callbacks are the same.

    'strict' arg has no meaning for python 3.8 onwards and will
    always return the equality of both callback based on 'self'
    comparison only.
    """
    if callback1 is callback2:
        # This happens when plain methods are given (or static/non-bound
        # methods).
        return True
    if callback1 == callback2:
        # NOTE(gmann): python3.8 onward, comparison of bound methods is
        # changed. It no longer decide the bound method's equality based
        # on their bounded objects equality instead it checks the identity
        # of their '__self__'. So python3.8 onward, two different bound
        # methods are no longer equal even __eq__ method return True.
        # Or in other term, 'strict' arg has no meaning from python 3.8
        # onwards above if condition never satisfy if both callback are
        # bounded to two different objects.
        # For backward compatibility for python <3.8, we can keep the 'strict'
        # arg and the below code of comparing 'self' and once minimum
        # supported python version is 3.8 we can remove both because python
        # 3.8 onward == operator itself checks identity of 'self'.
        # Ref bug: https://bugs.launchpad.net/oslo.utils/+bug/1841072
        if not strict:
            LOG.warning('"strict" arg is deprecated because it no '
                        'longer work for python 3.8 onwards')
            return True
        # Until python 3.7, two bound methods are equal if functions
        # themselves are equal and objects they are applied to are equal.
        # This means that a bound method could be the same bound method on
        # another object if the objects have __eq__ methods that return true
        # (when in fact it is a different bound method). Python u so crazy!
        try:
            self1 = operator.attrgetter("__self__")(callback1)
            self2 = operator.attrgetter("__self__")(callback2)
            return self1 is self2
        except AttributeError:  # nosec
            pass
    return False


def is_bound_method(method):
    """Returns if the given method is bound to an object."""
    return get_method_self(method) is not None


def is_subclass(obj, cls):
    """Returns if the object is class and it is subclass of a given class."""
    return inspect.isclass(obj) and issubclass(obj, cls)


def get_callable_args(function, required_only=False):
    """Get names of callable arguments.

    Special arguments (like ``*args`` and ``**kwargs``) are not included into
    output.

    If required_only is True, optional arguments (with default values)
    are not included into output.
    """
    sig = get_signature(function)
    function_args = list(iter(sig.parameters.keys()))
    for param_name, p in iter(sig.parameters.items()):
        if (p.kind in (Parameter.VAR_POSITIONAL, Parameter.VAR_KEYWORD) or
                (required_only and p.default is not Parameter.empty)):
            function_args.remove(param_name)
    return function_args


def accepts_kwargs(function):
    """Returns ``True`` if function accepts kwargs otherwise ``False``."""
    sig = get_signature(function)
    return any(p.kind == Parameter.VAR_KEYWORD
               for p in iter(sig.parameters.values()))