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venv/lib/python3.8/site-packages/astroid/bases.py

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+# -*- coding: utf-8 -*-
+# Copyright (c) 2009-2011, 2013-2014 LOGILAB S.A. (Paris, FRANCE) <contact@logilab.fr>
+# Copyright (c) 2012 FELD Boris <lothiraldan@gmail.com>
+# Copyright (c) 2014-2020 Claudiu Popa <pcmanticore@gmail.com>
+# Copyright (c) 2014 Google, Inc.
+# Copyright (c) 2014 Eevee (Alex Munroe) <amunroe@yelp.com>
+# Copyright (c) 2015-2016 Ceridwen <ceridwenv@gmail.com>
+# Copyright (c) 2015 Florian Bruhin <me@the-compiler.org>
+# Copyright (c) 2016-2017 Derek Gustafson <degustaf@gmail.com>
+# Copyright (c) 2017 Calen Pennington <calen.pennington@gmail.com>
+# Copyright (c) 2018-2019 hippo91 <guillaume.peillex@gmail.com>
+# Copyright (c) 2018 Ville Skyttä <ville.skytta@iki.fi>
+# Copyright (c) 2018 Bryce Guinta <bryce.paul.guinta@gmail.com>
+# Copyright (c) 2018 Nick Drozd <nicholasdrozd@gmail.com>
+# Copyright (c) 2018 Daniel Colascione <dancol@dancol.org>
+# Copyright (c) 2019 Hugo van Kemenade <hugovk@users.noreply.github.com>
+
+# Licensed under the LGPL: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html
+# For details: https://github.com/PyCQA/astroid/blob/master/COPYING.LESSER
+
+"""This module contains base classes and functions for the nodes and some
+inference utils.
+"""
+
+import builtins
+import collections
+
+from astroid import context as contextmod
+from astroid import exceptions
+from astroid import util
+
+objectmodel = util.lazy_import("interpreter.objectmodel")
+helpers = util.lazy_import("helpers")
+BUILTINS = builtins.__name__
+manager = util.lazy_import("manager")
+MANAGER = manager.AstroidManager()
+
+# TODO: check if needs special treatment
+BUILTINS = "builtins"
+BOOL_SPECIAL_METHOD = "__bool__"
+
+PROPERTIES = {BUILTINS + ".property", "abc.abstractproperty"}
+# List of possible property names. We use this list in order
+# to see if a method is a property or not. This should be
+# pretty reliable and fast, the alternative being to check each
+# decorator to see if its a real property-like descriptor, which
+# can be too complicated.
+# Also, these aren't qualified, because each project can
+# define them, we shouldn't expect to know every possible
+# property-like decorator!
+POSSIBLE_PROPERTIES = {
+    "cached_property",
+    "cachedproperty",
+    "lazyproperty",
+    "lazy_property",
+    "reify",
+    "lazyattribute",
+    "lazy_attribute",
+    "LazyProperty",
+    "lazy",
+    "cache_readonly",
+}
+
+
+def _is_property(meth, context=None):
+    decoratornames = meth.decoratornames(context=context)
+    if PROPERTIES.intersection(decoratornames):
+        return True
+    stripped = {
+        name.split(".")[-1] for name in decoratornames if name is not util.Uninferable
+    }
+    if any(name in stripped for name in POSSIBLE_PROPERTIES):
+        return True
+
+    # Lookup for subclasses of *property*
+    if not meth.decorators:
+        return False
+    for decorator in meth.decorators.nodes or ():
+        inferred = helpers.safe_infer(decorator, context=context)
+        if inferred is None or inferred is util.Uninferable:
+            continue
+        if inferred.__class__.__name__ == "ClassDef":
+            for base_class in inferred.bases:
+                if base_class.__class__.__name__ != "Name":
+                    continue
+                module, _ = base_class.lookup(base_class.name)
+                if module.name == BUILTINS and base_class.name == "property":
+                    return True
+
+    return False
+
+
+class Proxy:
+    """a simple proxy object
+
+    Note:
+
+    Subclasses of this object will need a custom __getattr__
+    if new instance attributes are created. See the Const class
+    """
+
+    _proxied = None  # proxied object may be set by class or by instance
+
+    def __init__(self, proxied=None):
+        if proxied is not None:
+            self._proxied = proxied
+
+    def __getattr__(self, name):
+        if name == "_proxied":
+            return getattr(self.__class__, "_proxied")
+        if name in self.__dict__:
+            return self.__dict__[name]
+        return getattr(self._proxied, name)
+
+    def infer(self, context=None):
+        yield self
+
+
+def _infer_stmts(stmts, context, frame=None):
+    """Return an iterator on statements inferred by each statement in *stmts*."""
+    inferred = False
+    if context is not None:
+        name = context.lookupname
+        context = context.clone()
+    else:
+        name = None
+        context = contextmod.InferenceContext()
+
+    for stmt in stmts:
+        if stmt is util.Uninferable:
+            yield stmt
+            inferred = True
+            continue
+        context.lookupname = stmt._infer_name(frame, name)
+        try:
+            for inferred in stmt.infer(context=context):
+                yield inferred
+                inferred = True
+        except exceptions.NameInferenceError:
+            continue
+        except exceptions.InferenceError:
+            yield util.Uninferable
+            inferred = True
+    if not inferred:
+        raise exceptions.InferenceError(
+            "Inference failed for all members of {stmts!r}.",
+            stmts=stmts,
+            frame=frame,
+            context=context,
+        )
+
+
+def _infer_method_result_truth(instance, method_name, context):
+    # Get the method from the instance and try to infer
+    # its return's truth value.
+    meth = next(instance.igetattr(method_name, context=context), None)
+    if meth and hasattr(meth, "infer_call_result"):
+        if not meth.callable():
+            return util.Uninferable
+        try:
+            for value in meth.infer_call_result(instance, context=context):
+                if value is util.Uninferable:
+                    return value
+
+                inferred = next(value.infer(context=context))
+                return inferred.bool_value()
+        except exceptions.InferenceError:
+            pass
+    return util.Uninferable
+
+
+class BaseInstance(Proxy):
+    """An instance base class, which provides lookup methods for potential instances."""
+
+    special_attributes = None
+
+    def display_type(self):
+        return "Instance of"
+
+    def getattr(self, name, context=None, lookupclass=True):
+        try:
+            values = self._proxied.instance_attr(name, context)
+        except exceptions.AttributeInferenceError as exc:
+            if self.special_attributes and name in self.special_attributes:
+                return [self.special_attributes.lookup(name)]
+
+            if lookupclass:
+                # Class attributes not available through the instance
+                # unless they are explicitly defined.
+                return self._proxied.getattr(name, context, class_context=False)
+
+            raise exceptions.AttributeInferenceError(
+                target=self, attribute=name, context=context
+            ) from exc
+        # since we've no context information, return matching class members as
+        # well
+        if lookupclass:
+            try:
+                return values + self._proxied.getattr(
+                    name, context, class_context=False
+                )
+            except exceptions.AttributeInferenceError:
+                pass
+        return values
+
+    def igetattr(self, name, context=None):
+        """inferred getattr"""
+        if not context:
+            context = contextmod.InferenceContext()
+        try:
+            # avoid recursively inferring the same attr on the same class
+            if context.push((self._proxied, name)):
+                raise exceptions.InferenceError(
+                    message="Cannot infer the same attribute again",
+                    node=self,
+                    context=context,
+                )
+
+            # XXX frame should be self._proxied, or not ?
+            get_attr = self.getattr(name, context, lookupclass=False)
+            yield from _infer_stmts(
+                self._wrap_attr(get_attr, context), context, frame=self
+            )
+        except exceptions.AttributeInferenceError as error:
+            try:
+                # fallback to class.igetattr since it has some logic to handle
+                # descriptors
+                # But only if the _proxied is the Class.
+                if self._proxied.__class__.__name__ != "ClassDef":
+                    raise
+                attrs = self._proxied.igetattr(name, context, class_context=False)
+                yield from self._wrap_attr(attrs, context)
+            except exceptions.AttributeInferenceError as error:
+                raise exceptions.InferenceError(**vars(error)) from error
+
+    def _wrap_attr(self, attrs, context=None):
+        """wrap bound methods of attrs in a InstanceMethod proxies"""
+        for attr in attrs:
+            if isinstance(attr, UnboundMethod):
+                if _is_property(attr):
+                    yield from attr.infer_call_result(self, context)
+                else:
+                    yield BoundMethod(attr, self)
+            elif hasattr(attr, "name") and attr.name == "<lambda>":
+                if attr.args.arguments and attr.args.arguments[0].name == "self":
+                    yield BoundMethod(attr, self)
+                    continue
+                yield attr
+            else:
+                yield attr
+
+    def infer_call_result(self, caller, context=None):
+        """infer what a class instance is returning when called"""
+        context = contextmod.bind_context_to_node(context, self)
+        inferred = False
+        for node in self._proxied.igetattr("__call__", context):
+            if node is util.Uninferable or not node.callable():
+                continue
+            for res in node.infer_call_result(caller, context):
+                inferred = True
+                yield res
+        if not inferred:
+            raise exceptions.InferenceError(node=self, caller=caller, context=context)
+
+
+class Instance(BaseInstance):
+    """A special node representing a class instance."""
+
+    # pylint: disable=unnecessary-lambda
+    special_attributes = util.lazy_descriptor(lambda: objectmodel.InstanceModel())
+
+    def __repr__(self):
+        return "<Instance of %s.%s at 0x%s>" % (
+            self._proxied.root().name,
+            self._proxied.name,
+            id(self),
+        )
+
+    def __str__(self):
+        return "Instance of %s.%s" % (self._proxied.root().name, self._proxied.name)
+
+    def callable(self):
+        try:
+            self._proxied.getattr("__call__", class_context=False)
+            return True
+        except exceptions.AttributeInferenceError:
+            return False
+
+    def pytype(self):
+        return self._proxied.qname()
+
+    def display_type(self):
+        return "Instance of"
+
+    def bool_value(self, context=None):
+        """Infer the truth value for an Instance
+
+        The truth value of an instance is determined by these conditions:
+
+           * if it implements __bool__ on Python 3 or __nonzero__
+             on Python 2, then its bool value will be determined by
+             calling this special method and checking its result.
+           * when this method is not defined, __len__() is called, if it
+             is defined, and the object is considered true if its result is
+             nonzero. If a class defines neither __len__() nor __bool__(),
+             all its instances are considered true.
+        """
+        context = context or contextmod.InferenceContext()
+        context.callcontext = contextmod.CallContext(args=[])
+        context.boundnode = self
+
+        try:
+            result = _infer_method_result_truth(self, BOOL_SPECIAL_METHOD, context)
+        except (exceptions.InferenceError, exceptions.AttributeInferenceError):
+            # Fallback to __len__.
+            try:
+                result = _infer_method_result_truth(self, "__len__", context)
+            except (exceptions.AttributeInferenceError, exceptions.InferenceError):
+                return True
+        return result
+
+    # This is set in inference.py.
+    def getitem(self, index, context=None):
+        pass
+
+
+class UnboundMethod(Proxy):
+    """a special node representing a method not bound to an instance"""
+
+    # pylint: disable=unnecessary-lambda
+    special_attributes = util.lazy_descriptor(lambda: objectmodel.UnboundMethodModel())
+
+    def __repr__(self):
+        frame = self._proxied.parent.frame()
+        return "<%s %s of %s at 0x%s" % (
+            self.__class__.__name__,
+            self._proxied.name,
+            frame.qname(),
+            id(self),
+        )
+
+    def implicit_parameters(self):
+        return 0
+
+    def is_bound(self):
+        return False
+
+    def getattr(self, name, context=None):
+        if name in self.special_attributes:
+            return [self.special_attributes.lookup(name)]
+        return self._proxied.getattr(name, context)
+
+    def igetattr(self, name, context=None):
+        if name in self.special_attributes:
+            return iter((self.special_attributes.lookup(name),))
+        return self._proxied.igetattr(name, context)
+
+    def infer_call_result(self, caller, context):
+        """
+        The boundnode of the regular context with a function called
+        on ``object.__new__`` will be of type ``object``,
+        which is incorrect for the argument in general.
+        If no context is given the ``object.__new__`` call argument will
+        correctly inferred except when inside a call that requires
+        the additional context (such as a classmethod) of the boundnode
+        to determine which class the method was called from
+        """
+
+        # If we're unbound method __new__ of builtin object, the result is an
+        # instance of the class given as first argument.
+        if (
+            self._proxied.name == "__new__"
+            and self._proxied.parent.frame().qname() == "%s.object" % BUILTINS
+        ):
+            if caller.args:
+                node_context = context.extra_context.get(caller.args[0])
+                infer = caller.args[0].infer(context=node_context)
+            else:
+                infer = []
+            return (Instance(x) if x is not util.Uninferable else x for x in infer)
+        return self._proxied.infer_call_result(caller, context)
+
+    def bool_value(self, context=None):
+        return True
+
+
+class BoundMethod(UnboundMethod):
+    """a special node representing a method bound to an instance"""
+
+    # pylint: disable=unnecessary-lambda
+    special_attributes = util.lazy_descriptor(lambda: objectmodel.BoundMethodModel())
+
+    def __init__(self, proxy, bound):
+        UnboundMethod.__init__(self, proxy)
+        self.bound = bound
+
+    def implicit_parameters(self):
+        if self.name == "__new__":
+            # __new__ acts as a classmethod but the class argument is not implicit.
+            return 0
+        return 1
+
+    def is_bound(self):
+        return True
+
+    def _infer_type_new_call(self, caller, context):
+        """Try to infer what type.__new__(mcs, name, bases, attrs) returns.
+
+        In order for such call to be valid, the metaclass needs to be
+        a subtype of ``type``, the name needs to be a string, the bases
+        needs to be a tuple of classes
+        """
+        # pylint: disable=import-outside-toplevel; circular import
+        from astroid import node_classes
+
+        # Verify the metaclass
+        mcs = next(caller.args[0].infer(context=context))
+        if mcs.__class__.__name__ != "ClassDef":
+            # Not a valid first argument.
+            return None
+        if not mcs.is_subtype_of("%s.type" % BUILTINS):
+            # Not a valid metaclass.
+            return None
+
+        # Verify the name
+        name = next(caller.args[1].infer(context=context))
+        if name.__class__.__name__ != "Const":
+            # Not a valid name, needs to be a const.
+            return None
+        if not isinstance(name.value, str):
+            # Needs to be a string.
+            return None
+
+        # Verify the bases
+        bases = next(caller.args[2].infer(context=context))
+        if bases.__class__.__name__ != "Tuple":
+            # Needs to be a tuple.
+            return None
+        inferred_bases = [next(elt.infer(context=context)) for elt in bases.elts]
+        if any(base.__class__.__name__ != "ClassDef" for base in inferred_bases):
+            # All the bases needs to be Classes
+            return None
+
+        # Verify the attributes.
+        attrs = next(caller.args[3].infer(context=context))
+        if attrs.__class__.__name__ != "Dict":
+            # Needs to be a dictionary.
+            return None
+        cls_locals = collections.defaultdict(list)
+        for key, value in attrs.items:
+            key = next(key.infer(context=context))
+            value = next(value.infer(context=context))
+            # Ignore non string keys
+            if key.__class__.__name__ == "Const" and isinstance(key.value, str):
+                cls_locals[key.value].append(value)
+
+        # Build the class from now.
+        cls = mcs.__class__(
+            name=name.value,
+            lineno=caller.lineno,
+            col_offset=caller.col_offset,
+            parent=caller,
+        )
+        empty = node_classes.Pass()
+        cls.postinit(
+            bases=bases.elts,
+            body=[empty],
+            decorators=[],
+            newstyle=True,
+            metaclass=mcs,
+            keywords=[],
+        )
+        cls.locals = cls_locals
+        return cls
+
+    def infer_call_result(self, caller, context=None):
+        context = contextmod.bind_context_to_node(context, self.bound)
+        if (
+            self.bound.__class__.__name__ == "ClassDef"
+            and self.bound.name == "type"
+            and self.name == "__new__"
+            and len(caller.args) == 4
+        ):
+            # Check if we have a ``type.__new__(mcs, name, bases, attrs)`` call.
+            new_cls = self._infer_type_new_call(caller, context)
+            if new_cls:
+                return iter((new_cls,))
+
+        return super(BoundMethod, self).infer_call_result(caller, context)
+
+    def bool_value(self, context=None):
+        return True
+
+
+class Generator(BaseInstance):
+    """a special node representing a generator.
+
+    Proxied class is set once for all in raw_building.
+    """
+
+    # pylint: disable=unnecessary-lambda
+    special_attributes = util.lazy_descriptor(lambda: objectmodel.GeneratorModel())
+
+    # pylint: disable=super-init-not-called
+    def __init__(self, parent=None):
+        self.parent = parent
+
+    def callable(self):
+        return False
+
+    def pytype(self):
+        return "%s.generator" % BUILTINS
+
+    def display_type(self):
+        return "Generator"
+
+    def bool_value(self, context=None):
+        return True
+
+    def __repr__(self):
+        return "<Generator(%s) l.%s at 0x%s>" % (
+            self._proxied.name,
+            self.lineno,
+            id(self),
+        )
+
+    def __str__(self):
+        return "Generator(%s)" % (self._proxied.name)
+
+
+class AsyncGenerator(Generator):
+    """Special node representing an async generator"""
+
+    def pytype(self):
+        return "%s.async_generator" % BUILTINS
+
+    def display_type(self):
+        return "AsyncGenerator"
+
+    def __repr__(self):
+        return "<AsyncGenerator(%s) l.%s at 0x%s>" % (
+            self._proxied.name,
+            self.lineno,
+            id(self),
+        )
+
+    def __str__(self):
+        return "AsyncGenerator(%s)" % (self._proxied.name)