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# Licensed under the LGPL: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html
# For details: https://github.com/PyCQA/astroid/blob/main/LICENSE
# Copyright (c) https://github.com/PyCQA/astroid/blob/main/CONTRIBUTORS.txt
"""This module contains base classes and functions for the nodes and some
inference utils.
"""
from __future__ import annotations
import collections
import collections.abc
import sys
from collections.abc import Sequence
from typing import TYPE_CHECKING, Any, ClassVar
from astroid import decorators, nodes
from astroid.const import PY310_PLUS
from astroid.context import (
CallContext,
InferenceContext,
bind_context_to_node,
copy_context,
)
from astroid.exceptions import (
AstroidTypeError,
AttributeInferenceError,
InferenceError,
NameInferenceError,
)
from astroid.typing import InferBinaryOp, InferenceErrorInfo, InferenceResult
from astroid.util import Uninferable, UninferableBase, lazy_descriptor, lazy_import
if sys.version_info >= (3, 8):
from typing import Literal
else:
from typing_extensions import Literal
if TYPE_CHECKING:
from astroid.constraint import Constraint
objectmodel = lazy_import("interpreter.objectmodel")
helpers = lazy_import("helpers")
manager = lazy_import("manager")
# TODO: check if needs special treatment
BOOL_SPECIAL_METHOD = "__bool__"
BUILTINS = "builtins" # TODO Remove in 2.8
PROPERTIES = {"builtins.property", "abc.abstractproperty"}
if PY310_PLUS:
PROPERTIES.add("enum.property")
# 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",
"DynamicClassAttribute",
}
def _is_property(meth, context: InferenceContext | None = None) -> bool:
decoratornames = meth.decoratornames(context=context)
if PROPERTIES.intersection(decoratornames):
return True
stripped = {
name.split(".")[-1]
for name in decoratornames
if not isinstance(name, UninferableBase)
}
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 isinstance(inferred, UninferableBase):
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: nodes.ClassDef | nodes.Lambda | Proxy | None = (
None # proxied object may be set by class or by instance
)
def __init__(
self, proxied: nodes.ClassDef | nodes.Lambda | Proxy | None = None
) -> None:
if proxied is None:
# This is a hack to allow calling this __init__ during bootstrapping of
# builtin classes and their docstrings.
# For Const, Generator, and UnionType nodes the _proxied attribute
# is set during bootstrapping
# as we first need to build the ClassDef that they can proxy.
# Thus, if proxied is None self should be a Const or Generator
# as that is the only way _proxied will be correctly set as a ClassDef.
assert isinstance(self, (nodes.Const, Generator, UnionType))
else:
self._proxied = proxied
def __getattr__(self, name):
if name == "_proxied":
return self.__class__._proxied
if name in self.__dict__:
return self.__dict__[name]
return getattr(self._proxied, name)
def infer( # type: ignore[return]
self, context: InferenceContext | None = None, **kwargs: Any
) -> collections.abc.Generator[InferenceResult, None, InferenceErrorInfo | None]:
yield self
def _infer_stmts(
stmts: Sequence[nodes.NodeNG | UninferableBase | Instance],
context: InferenceContext | None,
frame: nodes.NodeNG | Instance | None = None,
) -> collections.abc.Generator[InferenceResult, None, None]:
"""Return an iterator on statements inferred by each statement in *stmts*."""
inferred = False
constraint_failed = False
if context is not None:
name = context.lookupname
context = context.clone()
constraints = context.constraints.get(name, {})
else:
name = None
constraints = {}
context = InferenceContext()
for stmt in stmts:
if isinstance(stmt, UninferableBase):
yield stmt
inferred = True
continue
# 'context' is always InferenceContext and Instances get '_infer_name' from ClassDef
context.lookupname = stmt._infer_name(frame, name) # type: ignore[union-attr]
try:
stmt_constraints: set[Constraint] = set()
for constraint_stmt, potential_constraints in constraints.items():
if not constraint_stmt.parent_of(stmt):
stmt_constraints.update(potential_constraints)
for inf in stmt.infer(context=context):
if all(constraint.satisfied_by(inf) for constraint in stmt_constraints):
yield inf
inferred = True
else:
constraint_failed = True
except NameInferenceError:
continue
except InferenceError:
yield Uninferable
inferred = True
if not inferred and constraint_failed:
yield Uninferable
elif not inferred:
raise 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 Uninferable
try:
context.callcontext = CallContext(args=[], callee=meth)
for value in meth.infer_call_result(instance, context=context):
if isinstance(value, UninferableBase):
return value
try:
inferred = next(value.infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
return inferred.bool_value()
except InferenceError:
pass
return Uninferable
class BaseInstance(Proxy):
"""An instance base class, which provides lookup methods for potential
instances.
"""
special_attributes = None
def display_type(self) -> str:
return "Instance of"
def getattr(self, name, context: InferenceContext | None = None, lookupclass=True):
try:
values = self._proxied.instance_attr(name, context)
except 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 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 AttributeInferenceError:
pass
return values
def igetattr(self, name, context: InferenceContext | None = None):
"""Inferred getattr."""
if not context:
context = InferenceContext()
try:
context.lookupname = name
# avoid recursively inferring the same attr on the same class
if context.push(self._proxied):
raise 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 AttributeInferenceError:
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 AttributeInferenceError as error:
raise InferenceError(**vars(error)) from error
def _wrap_attr(self, attrs, context: InferenceContext | None = 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: nodes.Call | Proxy, context: InferenceContext | None = None
):
"""Infer what a class instance is returning when called."""
context = bind_context_to_node(context, self)
inferred = False
# If the call is an attribute on the instance, we infer the attribute itself
if isinstance(caller, nodes.Call) and isinstance(caller.func, nodes.Attribute):
for res in self.igetattr(caller.func.attrname, context):
inferred = True
yield res
# Otherwise we infer the call to the __call__ dunder normally
for node in self._proxied.igetattr("__call__", context):
if isinstance(node, UninferableBase) or not node.callable():
continue
for res in node.infer_call_result(caller, context):
inferred = True
yield res
if not inferred:
raise InferenceError(node=self, caller=caller, context=context)
class Instance(BaseInstance):
"""A special node representing a class instance."""
_proxied: nodes.ClassDef
# pylint: disable=unnecessary-lambda
special_attributes = lazy_descriptor(lambda: objectmodel.InstanceModel())
def __init__(self, proxied: nodes.ClassDef | None) -> None:
super().__init__(proxied)
infer_binary_op: ClassVar[InferBinaryOp[Instance]]
def __repr__(self) -> str:
return "<Instance of {}.{} at 0x{}>".format(
self._proxied.root().name, self._proxied.name, id(self)
)
def __str__(self) -> str:
return f"Instance of {self._proxied.root().name}.{self._proxied.name}"
def callable(self) -> bool:
try:
self._proxied.getattr("__call__", class_context=False)
return True
except AttributeInferenceError:
return False
def pytype(self) -> str:
return self._proxied.qname()
def display_type(self) -> str:
return "Instance of"
def bool_value(self, context: InferenceContext | None = 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 InferenceContext()
context.boundnode = self
try:
result = _infer_method_result_truth(self, BOOL_SPECIAL_METHOD, context)
except (InferenceError, AttributeInferenceError):
# Fallback to __len__.
try:
result = _infer_method_result_truth(self, "__len__", context)
except (AttributeInferenceError, InferenceError):
return True
return result
def getitem(self, index, context: InferenceContext | None = None):
new_context = bind_context_to_node(context, self)
if not context:
context = new_context
method = next(self.igetattr("__getitem__", context=context), None)
# Create a new CallContext for providing index as an argument.
new_context.callcontext = CallContext(args=[index], callee=method)
if not isinstance(method, BoundMethod):
raise InferenceError(
"Could not find __getitem__ for {node!r}.", node=self, context=context
)
if len(method.args.arguments) != 2: # (self, index)
raise AstroidTypeError(
"__getitem__ for {node!r} does not have correct signature",
node=self,
context=context,
)
return next(method.infer_call_result(self, new_context), None)
class UnboundMethod(Proxy):
"""A special node representing a method not bound to an instance."""
# pylint: disable=unnecessary-lambda
special_attributes = lazy_descriptor(lambda: objectmodel.UnboundMethodModel())
def __repr__(self) -> str:
frame = self._proxied.parent.frame(future=True)
return "<{} {} of {} at 0x{}".format(
self.__class__.__name__, self._proxied.name, frame.qname(), id(self)
)
def implicit_parameters(self) -> Literal[0]:
return 0
def is_bound(self) -> Literal[False]:
return False
def getattr(self, name, context: InferenceContext | None = None):
if name in self.special_attributes:
return [self.special_attributes.lookup(name)]
return self._proxied.getattr(name, context)
def igetattr(self, name, context: InferenceContext | None = 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
be 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 a builtin, the result is an
# instance of the class given as first argument.
if self._proxied.name == "__new__":
qname = self._proxied.parent.frame(future=True).qname()
# Avoid checking builtins.type: _infer_type_new_call() does more validation
if qname.startswith("builtins.") and qname != "builtins.type":
return self._infer_builtin_new(caller, context)
return self._proxied.infer_call_result(caller, context)
def _infer_builtin_new(
self,
caller: nodes.Call,
context: InferenceContext,
) -> collections.abc.Generator[
nodes.Const | Instance | UninferableBase, None, None
]:
if not caller.args:
return
# Attempt to create a constant
if len(caller.args) > 1:
value = None
if isinstance(caller.args[1], nodes.Const):
value = caller.args[1].value
else:
inferred_arg = next(caller.args[1].infer(), None)
if isinstance(inferred_arg, nodes.Const):
value = inferred_arg.value
if value is not None:
yield nodes.const_factory(value)
return
node_context = context.extra_context.get(caller.args[0])
for inferred in caller.args[0].infer(context=node_context):
if isinstance(inferred, UninferableBase):
yield inferred
if isinstance(inferred, nodes.ClassDef):
yield Instance(inferred)
raise InferenceError
def bool_value(self, context: InferenceContext | None = None) -> Literal[True]:
return True
class BoundMethod(UnboundMethod):
"""A special node representing a method bound to an instance."""
# pylint: disable=unnecessary-lambda
special_attributes = lazy_descriptor(lambda: objectmodel.BoundMethodModel())
def __init__(self, proxy, bound):
super().__init__(proxy)
self.bound = bound
def implicit_parameters(self) -> Literal[0, 1]:
if self.name == "__new__":
# __new__ acts as a classmethod but the class argument is not implicit.
return 0
return 1
def is_bound(self) -> Literal[True]:
return True
def _infer_type_new_call(self, caller, context): # noqa: C901
"""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.nodes import Pass
# Verify the metaclass
try:
mcs = next(caller.args[0].infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
if mcs.__class__.__name__ != "ClassDef":
# Not a valid first argument.
return None
if not mcs.is_subtype_of("builtins.type"):
# Not a valid metaclass.
return None
# Verify the name
try:
name = next(caller.args[1].infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
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
try:
bases = next(caller.args[2].infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
if bases.__class__.__name__ != "Tuple":
# Needs to be a tuple.
return None
try:
inferred_bases = [next(elt.infer(context=context)) for elt in bases.elts]
except StopIteration as e:
raise InferenceError(context=context) from e
if any(base.__class__.__name__ != "ClassDef" for base in inferred_bases):
# All the bases needs to be Classes
return None
# Verify the attributes.
try:
attrs = next(caller.args[3].infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
if attrs.__class__.__name__ != "Dict":
# Needs to be a dictionary.
return None
cls_locals = collections.defaultdict(list)
for key, value in attrs.items:
try:
key = next(key.infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
try:
value = next(value.infer(context=context))
except StopIteration as e:
raise InferenceError(context=context) from e
# 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 = 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: InferenceContext | None = None):
context = 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().infer_call_result(caller, context)
def bool_value(self, context: InferenceContext | None = None) -> Literal[True]:
return True
class Generator(BaseInstance):
"""A special node representing a generator.
Proxied class is set once for all in raw_building.
"""
_proxied: nodes.ClassDef
special_attributes = lazy_descriptor(objectmodel.GeneratorModel)
def __init__(
self, parent=None, generator_initial_context: InferenceContext | None = None
):
super().__init__()
self.parent = parent
self._call_context = copy_context(generator_initial_context)
@decorators.cached
def infer_yield_types(self):
yield from self.parent.infer_yield_result(self._call_context)
def callable(self) -> Literal[False]:
return False
def pytype(self) -> Literal["builtins.generator"]:
return "builtins.generator"
def display_type(self) -> str:
return "Generator"
def bool_value(self, context: InferenceContext | None = None) -> Literal[True]:
return True
def __repr__(self) -> str:
return f"<Generator({self._proxied.name}) l.{self.lineno} at 0x{id(self)}>"
def __str__(self) -> str:
return f"Generator({self._proxied.name})"
class AsyncGenerator(Generator):
"""Special node representing an async generator."""
def pytype(self) -> Literal["builtins.async_generator"]:
return "builtins.async_generator"
def display_type(self) -> str:
return "AsyncGenerator"
def __repr__(self) -> str:
return f"<AsyncGenerator({self._proxied.name}) l.{self.lineno} at 0x{id(self)}>"
def __str__(self) -> str:
return f"AsyncGenerator({self._proxied.name})"
class UnionType(BaseInstance):
"""Special node representing new style typing unions.
Proxied class is set once for all in raw_building.
"""
_proxied: nodes.ClassDef
def __init__(
self,
left: UnionType | nodes.ClassDef | nodes.Const,
right: UnionType | nodes.ClassDef | nodes.Const,
parent: nodes.NodeNG | None = None,
) -> None:
super().__init__()
self.parent = parent
self.left = left
self.right = right
def callable(self) -> Literal[False]:
return False
def bool_value(self, context: InferenceContext | None = None) -> Literal[True]:
return True
def pytype(self) -> Literal["types.UnionType"]:
return "types.UnionType"
def display_type(self) -> str:
return "UnionType"
def __repr__(self) -> str:
return f"<UnionType({self._proxied.name}) l.{self.lineno} at 0x{id(self)}>"
def __str__(self) -> str:
return f"UnionType({self._proxied.name})"