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bpython-apipkg-execnet / bpython / inspection.py

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# The MIT License
#
# Copyright (c) 2009-2010 the bpython authors.
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.
#

from __future__ import with_statement
import collections
import inspect
import keyword
import pydoc
import re
import sys
import types

from pygments.lexers import PythonLexer
from pygments.token import Token

try:
    collections.Callable
    has_collections_callable = True
except AttributeError:
    has_collections_callable = False
try:
    types.InstanceType
    has_instance_type = True
except AttributeError:
    has_instance_type = False

py3 = sys.version_info[0] == 3

if not py3:
    _name = re.compile(r'[a-zA-Z_]\w*$')


class AttrCleaner(object):
    """A context manager that tries to make an object not exhibit side-effects
       on attribute lookup."""

    def __init__(self, obj):
        self.obj = obj

    def __enter__(self):
        """Try to make an object not exhibit side-effects on attribute
        lookup."""
        type_ = type(self.obj)
        __getattribute__ = None
        __getattr__ = None
        # Dark magic:
        # If __getattribute__ doesn't exist on the class and __getattr__ does
        # then __getattr__ will be called when doing
        #   getattr(type_, '__getattribute__', None)
        # so we need to first remove the __getattr__, then the
        # __getattribute__, then look up the attributes and then restore the
        # original methods. :-(
        # The upshot being that introspecting on an object to display its
        # attributes will avoid unwanted side-effects.
        if py3 or type_ != types.InstanceType:
            __getattr__ = getattr(type_, '__getattr__', None)
            if __getattr__ is not None:
                try:
                    setattr(type_, '__getattr__', (lambda *_, **__: None))
                except TypeError:
                    __getattr__ = None
            __getattribute__ = getattr(type_, '__getattribute__', None)
            if __getattribute__ is not None:
                try:
                    setattr(type_, '__getattribute__', object.__getattribute__)
                except TypeError:
                    # XXX: This happens for e.g. built-in types
                    __getattribute__ = None
        self.attribs = (__getattribute__, __getattr__)
        # /Dark magic

    def __exit__(self, exc_type, exc_val, exc_tb):
        """Restore an object's magic methods."""
        type_ = type(self.obj)
        __getattribute__, __getattr__ = self.attribs
        # Dark magic:
        if __getattribute__ is not None:
            setattr(type_, '__getattribute__', __getattribute__)
        if __getattr__ is not None:
            setattr(type_, '__getattr__', __getattr__)
        # /Dark magic


def parsekeywordpairs(signature):
    tokens = PythonLexer().get_tokens(signature)
    stack = []
    substack = []
    parendepth = 0
    begin = False
    for token, value in tokens:
        if not begin:
            if token is Token.Punctuation and value == u'(':
                begin = True
            continue

        if token is Token.Punctuation:
            if value == u'(':
                parendepth += 1
            elif value == u')':
                parendepth -= 1
            elif value == ':' and parendepth == -1:
                # End of signature reached
                break

        if parendepth > 0:
            substack.append(value)
            continue

        if (token is Token.Punctuation and
            (value == ',' or (value == ')' and parendepth == -1))):
            stack.append(substack[:])
            del substack[:]
            continue

        if value and value.strip():
            substack.append(value)

    d = {}
    for item in stack:
        if len(item) >= 3:
            d[item[0]] = ''.join(item[2:])
    return d


def fixlongargs(f, argspec):
    """Functions taking default arguments that are references to other objects
    whose str() is too big will cause breakage, so we swap out the object
    itself with the name it was referenced with in the source by parsing the
    source itself !"""
    if argspec[3] is None:
        # No keyword args, no need to do anything
        return
    values = list(argspec[3])
    if not values:
        return
    keys = argspec[0][-len(values):]
    try:
        src = inspect.getsourcelines(f)
    except (IOError, IndexError):
        # IndexError is raised in inspect.findsource(), can happen in
        # some situations. See issue #94.
        return
    signature = ''.join(src[0])
    kwparsed = parsekeywordpairs(signature)

    for i, (key, value) in enumerate(zip(keys, values)):
        if len(str(value)) != len(kwparsed[key]):
            values[i] = kwparsed[key]

    argspec[3] = values


def getpydocspec(f, func):
    try:
        argspec = pydoc.getdoc(f)
    except NameError:
        return None

    rx = re.compile(r'([a-zA-Z_][a-zA-Z0-9_]*?)\((.*?)\)')
    s = rx.search(argspec)
    if s is None:
        return None

    if not hasattr(f, '__name__') or s.groups()[0] != f.__name__:
        return None

    args = list()
    defaults = list()
    varargs = varkwargs = None
    kwonly_args = list()
    kwonly_defaults = dict()
    for arg in s.group(2).split(','):
        arg = arg.strip()
        if arg.startswith('**'):
            varkwargs = arg[2:]
        elif arg.startswith('*'):
            varargs = arg[1:]
        else:
            arg, _, default = arg.partition('=')
            if varargs is not None:
                kwonly_args.append(arg)
                if default:
                    kwonly_defaults[arg] = default
            else:
                args.append(arg)
                if default:
                    defaults.append(default)

    return [func, (args, varargs, varkwargs, defaults,
                   kwonly_args, kwonly_defaults)]


def getargspec(func, f):
    # Check if it's a real bound method or if it's implicitly calling __init__
    # (i.e. FooClass(...) and not FooClass.__init__(...) -- the former would
    # not take 'self', the latter would:
    func_name = getattr(f, '__name__', None)

    is_bound_method = ((inspect.ismethod(f) and f.im_self is not None)
                    or (func_name == '__init__' and not
                        func.endswith('.__init__')))
    try:
        if py3:
            argspec = inspect.getfullargspec(f)
        else:
            argspec = inspect.getargspec(f)

        argspec = list(argspec)
        fixlongargs(f, argspec)
        argspec = [func, argspec, is_bound_method]
    except (TypeError, KeyError):
        with AttrCleaner(f):
            argspec = getpydocspec(f, func)
        if argspec is None:
            return None
        if inspect.ismethoddescriptor(f):
            argspec[1][0].insert(0, 'obj')
        argspec.append(is_bound_method)
    return argspec


def is_eval_safe_name(string):
    if py3:
        return all(part.isidentifier() and not keyword.iskeyword(part)
                   for part in string.split('.'))
    else:
        return all(_name.match(part) and not keyword.iskeyword(part)
                   for part in string.split('.'))


def is_callable(obj):
    if has_instance_type and isinstance(obj, types.InstanceType):
        # Work around a Python bug, see issue 7624
        return callable(obj)
    elif has_collections_callable:
        return isinstance(obj, collections.Callable)
    else:
        return callable(obj)