objectmodel.py

# Copyright (c) 2016-2018 Claudiu Popa <pcmanticore@gmail.com>
# Copyright (c) 2016 Derek Gustafson <degustaf@gmail.com>
# Copyright (c) 2017-2018 Bryce Guinta <bryce.paul.guinta@gmail.com>
# Copyright (c) 2017 Ceridwen <ceridwenv@gmail.com>
# Copyright (c) 2017 Calen Pennington <cale@edx.org>
# Copyright (c) 2018 Nick Drozd <nicholasdrozd@gmail.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
"""
Data object model, as per https://docs.python.org/3/reference/datamodel.html.

This module describes, at least partially, a data object model for some
of astroid's nodes. The model contains special attributes that nodes such
as functions, classes, modules etc have, such as __doc__, __class__,
__module__ etc, being used when doing attribute lookups over nodes.

For instance, inferring `obj.__class__` will first trigger an inference
of the `obj` variable. If it was successfully inferred, then an attribute
`__class__ will be looked for in the inferred object. This is the part
where the data model occurs. The model is attached to those nodes
and the lookup mechanism will try to see if attributes such as
`__class__` are defined by the model or not. If they are defined,
the model will be requested to return the corresponding value of that
attribute. Thus the model can be viewed as a special part of the lookup
mechanism.
"""

import itertools
import pprint
import os
import types
from functools import lru_cache

import astroid
from astroid import context as contextmod
from astroid import exceptions
from astroid import node_classes


IMPL_PREFIX = "attr_"


def _dunder_dict(instance, attributes):
    obj = node_classes.Dict(parent=instance)

    # Convert the keys to node strings
    keys = [
        node_classes.Const(value=value, parent=obj) for value in list(attributes.keys())
    ]

    # The original attribute has a list of elements for each key,
    # but that is not useful for retrieving the special attribute's value.
    # In this case, we're picking the last value from each list.
    values = [elem[-1] for elem in attributes.values()]

    obj.postinit(list(zip(keys, values)))
    return obj


class ObjectModel:
    def __init__(self):
        self._instance = None

    def __repr__(self):
        result = []
        cname = type(self).__name__
        string = "%(cname)s(%(fields)s)"
        alignment = len(cname) + 1
        for field in sorted(self.attributes()):
            width = 80 - len(field) - alignment
            lines = pprint.pformat(field, indent=2, width=width).splitlines(True)

            inner = [lines[0]]
            for line in lines[1:]:
                inner.append(" " * alignment + line)
            result.append(field)

        return string % {
            "cname": cname,
            "fields": (",\n" + " " * alignment).join(result),
        }

    def __call__(self, instance):
        self._instance = instance
        return self

    def __get__(self, instance, cls=None):
        # ObjectModel needs to be a descriptor so that just doing
        # `special_attributes = SomeObjectModel` should be enough in the body of a node.
        # But at the same time, node.special_attributes should return an object
        # which can be used for manipulating the special attributes. That's the reason
        # we pass the instance through which it got accessed to ObjectModel.__call__,
        # returning itself afterwards, so we can still have access to the
        # underlying data model and to the instance for which it got accessed.
        return self(instance)

    def __contains__(self, name):
        return name in self.attributes()

    @lru_cache(maxsize=None)
    def attributes(self):
        """Get the attributes which are exported by this object model."""
        return [
            obj[len(IMPL_PREFIX) :] for obj in dir(self) if obj.startswith(IMPL_PREFIX)
        ]

    def lookup(self, name):
        """Look up the given *name* in the current model

        It should return an AST or an interpreter object,
        but if the name is not found, then an AttributeInferenceError will be raised.
        """

        if name in self.attributes():
            return getattr(self, IMPL_PREFIX + name)
        raise exceptions.AttributeInferenceError(target=self._instance, attribute=name)


class ModuleModel(ObjectModel):
    def _builtins(self):
        builtins_ast_module = astroid.MANAGER.builtins_module
        return builtins_ast_module.special_attributes.lookup("__dict__")

    @property
    def attr_builtins(self):
        return self._builtins()

    @property
    def attr___path__(self):
        if not self._instance.package:
            raise exceptions.AttributeInferenceError(
                target=self._instance, attribute="__path__"
            )

        path_objs = [
            node_classes.Const(
                value=path
                if not path.endswith("__init__.py")
                else os.path.dirname(path),
                parent=self._instance,
            )
            for path in self._instance.path
        ]

        container = node_classes.List(parent=self._instance)
        container.postinit(path_objs)

        return container

    @property
    def attr___name__(self):
        return node_classes.Const(value=self._instance.name, parent=self._instance)

    @property
    def attr___doc__(self):
        return node_classes.Const(value=self._instance.doc, parent=self._instance)

    @property
    def attr___file__(self):
        return node_classes.Const(value=self._instance.file, parent=self._instance)

    @property
    def attr___dict__(self):
        return _dunder_dict(self._instance, self._instance.globals)

    @property
    def attr___package__(self):
        if not self._instance.package:
            value = ""
        else:
            value = self._instance.name

        return node_classes.Const(value=value, parent=self._instance)

    # These are related to the Python 3 implementation of the
    # import system,
    # https://docs.python.org/3/reference/import.html#import-related-module-attributes

    @property
    def attr___spec__(self):
        # No handling for now.
        return node_classes.Unknown()

    @property
    def attr___loader__(self):
        # No handling for now.
        return node_classes.Unknown()

    @property
    def attr___cached__(self):
        # No handling for now.
        return node_classes.Unknown()


class FunctionModel(ObjectModel):
    @property
    def attr___name__(self):
        return node_classes.Const(value=self._instance.name, parent=self._instance)

    @property
    def attr___doc__(self):
        return node_classes.Const(value=self._instance.doc, parent=self._instance)

    @property
    def attr___qualname__(self):
        return node_classes.Const(value=self._instance.qname(), parent=self._instance)

    @property
    def attr___defaults__(self):
        func = self._instance
        if not func.args.defaults:
            return node_classes.Const(value=None, parent=func)

        defaults_obj = node_classes.Tuple(parent=func)
        defaults_obj.postinit(func.args.defaults)
        return defaults_obj

    @property
    def attr___annotations__(self):
        obj = node_classes.Dict(parent=self._instance)

        if not self._instance.returns:
            returns = None
        else:
            returns = self._instance.returns

        args = self._instance.args
        pair_annotations = itertools.chain(
            zip(args.args or [], args.annotations),
            zip(args.kwonlyargs, args.kwonlyargs_annotations),
            zip(args.posonlyargs or [], args.posonlyargs_annotations),
        )

        annotations = {
            arg.name: annotation for (arg, annotation) in pair_annotations if annotation
        }
        if args.varargannotation:
            annotations[args.vararg] = args.varargannotation
        if args.kwargannotation:
            annotations[args.kwarg] = args.kwargannotation
        if returns:
            annotations["return"] = returns

        items = [
            (node_classes.Const(key, parent=obj), value)
            for (key, value) in annotations.items()
        ]

        obj.postinit(items)
        return obj

    @property
    def attr___dict__(self):
        return node_classes.Dict(parent=self._instance)

    attr___globals__ = attr___dict__

    @property
    def attr___kwdefaults__(self):
        def _default_args(args, parent):
            for arg in args.kwonlyargs:
                try:
                    default = args.default_value(arg.name)
                except exceptions.NoDefault:
                    continue

                name = node_classes.Const(arg.name, parent=parent)
                yield name, default

        args = self._instance.args
        obj = node_classes.Dict(parent=self._instance)
        defaults = dict(_default_args(args, obj))

        obj.postinit(list(defaults.items()))
        return obj

    @property
    def attr___module__(self):
        return node_classes.Const(self._instance.root().qname())

    @property
    def attr___get__(self):
        # pylint: disable=import-outside-toplevel; circular import
        from astroid import bases

        func = self._instance

        class DescriptorBoundMethod(bases.BoundMethod):
            """Bound method which knows how to understand calling descriptor binding."""

            def implicit_parameters(self):
                # Different than BoundMethod since the signature
                # is different.
                return 0

            def infer_call_result(self, caller, context=None):
                if len(caller.args) > 2 or len(caller.args) < 1:
                    raise exceptions.InferenceError(
                        "Invalid arguments for descriptor binding",
                        target=self,
                        context=context,
                    )

                context = contextmod.copy_context(context)
                cls = next(caller.args[0].infer(context=context))

                if cls is astroid.Uninferable:
                    raise exceptions.InferenceError(
                        "Invalid class inferred", target=self, context=context
                    )

                # For some reason func is a Node that the below
                # code is not expecting
                if isinstance(func, bases.BoundMethod):
                    yield func
                    return

                # Rebuild the original value, but with the parent set as the
                # class where it will be bound.
                new_func = func.__class__(
                    name=func.name,
                    doc=func.doc,
                    lineno=func.lineno,
                    col_offset=func.col_offset,
                    parent=cls,
                )
                # pylint: disable=no-member
                new_func.postinit(func.args, func.body, func.decorators, func.returns)

                # Build a proper bound method that points to our newly built function.
                proxy = bases.UnboundMethod(new_func)
                yield bases.BoundMethod(proxy=proxy, bound=cls)

            @property
            def args(self):
                """Overwrite the underlying args to match those of the underlying func

                Usually the underlying *func* is a function/method, as in:

                    def test(self):
                        pass

                This has only the *self* parameter but when we access test.__get__
                we get a new object which has two parameters, *self* and *type*.
                """
                nonlocal func
                positional_or_keyword_params = func.args.args.copy()
                positional_or_keyword_params.append(astroid.AssignName(name="type"))

                positional_only_params = func.args.posonlyargs.copy()

                arguments = astroid.Arguments(parent=func.args.parent)
                arguments.postinit(
                    args=positional_or_keyword_params,
                    posonlyargs=positional_only_params,
                    defaults=[],
                    kwonlyargs=[],
                    kw_defaults=[],
                    annotations=[],
                )
                return arguments

        return DescriptorBoundMethod(proxy=self._instance, bound=self._instance)

    # These are here just for completion.
    @property
    def attr___ne__(self):
        return node_classes.Unknown()

    attr___subclasshook__ = attr___ne__
    attr___str__ = attr___ne__
    attr___sizeof__ = attr___ne__
    attr___setattr___ = attr___ne__
    attr___repr__ = attr___ne__
    attr___reduce__ = attr___ne__
    attr___reduce_ex__ = attr___ne__
    attr___new__ = attr___ne__
    attr___lt__ = attr___ne__
    attr___eq__ = attr___ne__
    attr___gt__ = attr___ne__
    attr___format__ = attr___ne__
    attr___delattr___ = attr___ne__
    attr___getattribute__ = attr___ne__
    attr___hash__ = attr___ne__
    attr___init__ = attr___ne__
    attr___dir__ = attr___ne__
    attr___call__ = attr___ne__
    attr___class__ = attr___ne__
    attr___closure__ = attr___ne__
    attr___code__ = attr___ne__


class ClassModel(ObjectModel):
    @property
    def attr___module__(self):
        return node_classes.Const(self._instance.root().qname())

    @property
    def attr___name__(self):
        return node_classes.Const(self._instance.name)

    @property
    def attr___qualname__(self):
        return node_classes.Const(self._instance.qname())

    @property
    def attr___doc__(self):
        return node_classes.Const(self._instance.doc)

    @property
    def attr___mro__(self):
        if not self._instance.newstyle:
            raise exceptions.AttributeInferenceError(
                target=self._instance, attribute="__mro__"
            )

        mro = self._instance.mro()
        obj = node_classes.Tuple(parent=self._instance)
        obj.postinit(mro)
        return obj

    @property
    def attr_mro(self):
        if not self._instance.newstyle:
            raise exceptions.AttributeInferenceError(
                target=self._instance, attribute="mro"
            )

        # pylint: disable=import-outside-toplevel; circular import
        from astroid import bases

        other_self = self

        # Cls.mro is a method and we need to return one in order to have a proper inference.
        # The method we're returning is capable of inferring the underlying MRO though.
        class MroBoundMethod(bases.BoundMethod):
            def infer_call_result(self, caller, context=None):
                yield other_self.attr___mro__

        implicit_metaclass = self._instance.implicit_metaclass()
        mro_method = implicit_metaclass.locals["mro"][0]
        return MroBoundMethod(proxy=mro_method, bound=implicit_metaclass)

    @property
    def attr___bases__(self):
        obj = node_classes.Tuple()
        context = contextmod.InferenceContext()
        elts = list(self._instance._inferred_bases(context))
        obj.postinit(elts=elts)
        return obj

    @property
    def attr___class__(self):
        # pylint: disable=import-outside-toplevel; circular import
        from astroid import helpers

        return helpers.object_type(self._instance)

    @property
    def attr___subclasses__(self):
        """Get the subclasses of the underlying class

        This looks only in the current module for retrieving the subclasses,
        thus it might miss a couple of them.
        """
        # pylint: disable=import-outside-toplevel; circular import
        from astroid import bases
        from astroid import scoped_nodes

        if not self._instance.newstyle:
            raise exceptions.AttributeInferenceError(
                target=self._instance, attribute="__subclasses__"
            )

        qname = self._instance.qname()
        root = self._instance.root()
        classes = [
            cls
            for cls in root.nodes_of_class(scoped_nodes.ClassDef)
            if cls != self._instance and cls.is_subtype_of(qname)
        ]

        obj = node_classes.List(parent=self._instance)
        obj.postinit(classes)

        class SubclassesBoundMethod(bases.BoundMethod):
            def infer_call_result(self, caller, context=None):
                yield obj

        implicit_metaclass = self._instance.implicit_metaclass()
        subclasses_method = implicit_metaclass.locals["__subclasses__"][0]
        return SubclassesBoundMethod(proxy=subclasses_method, bound=implicit_metaclass)

    @property
    def attr___dict__(self):
        return node_classes.Dict(parent=self._instance)


class SuperModel(ObjectModel):
    @property
    def attr___thisclass__(self):
        return self._instance.mro_pointer

    @property
    def attr___self_class__(self):
        return self._instance._self_class

    @property
    def attr___self__(self):
        return self._instance.type

    @property
    def attr___class__(self):
        return self._instance._proxied


class UnboundMethodModel(ObjectModel):
    @property
    def attr___class__(self):
        # pylint: disable=import-outside-toplevel; circular import
        from astroid import helpers

        return helpers.object_type(self._instance)

    @property
    def attr___func__(self):
        return self._instance._proxied

    @property
    def attr___self__(self):
        return node_classes.Const(value=None, parent=self._instance)

    attr_im_func = attr___func__
    attr_im_class = attr___class__
    attr_im_self = attr___self__


class BoundMethodModel(FunctionModel):
    @property
    def attr___func__(self):
        return self._instance._proxied._proxied

    @property
    def attr___self__(self):
        return self._instance.bound


class GeneratorModel(FunctionModel):
    def __new__(cls, *args, **kwargs):
        # Append the values from the GeneratorType unto this object.
        ret = super(GeneratorModel, cls).__new__(cls, *args, **kwargs)
        generator = astroid.MANAGER.builtins_module["generator"]
        for name, values in generator.locals.items():
            method = values[0]
            patched = lambda cls, meth=method: meth

            setattr(type(ret), IMPL_PREFIX + name, property(patched))

        return ret

    @property
    def attr___name__(self):
        return node_classes.Const(
            value=self._instance.parent.name, parent=self._instance
        )

    @property
    def attr___doc__(self):
        return node_classes.Const(
            value=self._instance.parent.doc, parent=self._instance
        )


class AsyncGeneratorModel(GeneratorModel):
    def __new__(cls, *args, **kwargs):
        # Append the values from the AGeneratorType unto this object.
        ret = super().__new__(cls, *args, **kwargs)
        astroid_builtins = astroid.MANAGER.builtins_module
        generator = astroid_builtins.get("async_generator")
        if generator is None:
            # Make it backward compatible.
            generator = astroid_builtins.get("generator")

        for name, values in generator.locals.items():
            method = values[0]
            patched = lambda cls, meth=method: meth

            setattr(type(ret), IMPL_PREFIX + name, property(patched))

        return ret


class InstanceModel(ObjectModel):
    @property
    def attr___class__(self):
        return self._instance._proxied

    @property
    def attr___module__(self):
        return node_classes.Const(self._instance.root().qname())

    @property
    def attr___doc__(self):
        return node_classes.Const(self._instance.doc)

    @property
    def attr___dict__(self):
        return _dunder_dict(self._instance, self._instance.instance_attrs)


# Exception instances


class ExceptionInstanceModel(InstanceModel):
    @property
    def attr_args(self):
        message = node_classes.Const("")
        args = node_classes.Tuple(parent=self._instance)
        args.postinit((message,))
        return args

    @property
    def attr___traceback__(self):
        builtins_ast_module = astroid.MANAGER.builtins_module
        traceback_type = builtins_ast_module[types.TracebackType.__name__]
        return traceback_type.instantiate_class()


class SyntaxErrorInstanceModel(ExceptionInstanceModel):
    @property
    def attr_text(self):
        return node_classes.Const("")


class OSErrorInstanceModel(ExceptionInstanceModel):
    @property
    def attr_filename(self):
        return node_classes.Const("")

    @property
    def attr_errno(self):
        return node_classes.Const(0)

    @property
    def attr_strerror(self):
        return node_classes.Const("")

    attr_filename2 = attr_filename


class ImportErrorInstanceModel(ExceptionInstanceModel):
    @property
    def attr_name(self):
        return node_classes.Const("")

    @property
    def attr_path(self):
        return node_classes.Const("")


BUILTIN_EXCEPTIONS = {
    "builtins.SyntaxError": SyntaxErrorInstanceModel,
    "builtins.ImportError": ImportErrorInstanceModel,
    # These are all similar to OSError in terms of attributes
    "builtins.OSError": OSErrorInstanceModel,
    "builtins.BlockingIOError": OSErrorInstanceModel,
    "builtins.BrokenPipeError": OSErrorInstanceModel,
    "builtins.ChildProcessError": OSErrorInstanceModel,
    "builtins.ConnectionAbortedError": OSErrorInstanceModel,
    "builtins.ConnectionError": OSErrorInstanceModel,
    "builtins.ConnectionRefusedError": OSErrorInstanceModel,
    "builtins.ConnectionResetError": OSErrorInstanceModel,
    "builtins.FileExistsError": OSErrorInstanceModel,
    "builtins.FileNotFoundError": OSErrorInstanceModel,
    "builtins.InterruptedError": OSErrorInstanceModel,
    "builtins.IsADirectoryError": OSErrorInstanceModel,
    "builtins.NotADirectoryError": OSErrorInstanceModel,
    "builtins.PermissionError": OSErrorInstanceModel,
    "builtins.ProcessLookupError": OSErrorInstanceModel,
    "builtins.TimeoutError": OSErrorInstanceModel,
}


class DictModel(ObjectModel):
    @property
    def attr___class__(self):
        return self._instance._proxied

    def _generic_dict_attribute(self, obj, name):
        """Generate a bound method that can infer the given *obj*."""

        class DictMethodBoundMethod(astroid.BoundMethod):
            def infer_call_result(self, caller, context=None):
                yield obj

        meth = next(self._instance._proxied.igetattr(name))
        return DictMethodBoundMethod(proxy=meth, bound=self._instance)

    @property
    def attr_items(self):
        elems = []
        obj = node_classes.List(parent=self._instance)
        for key, value in self._instance.items:
            elem = node_classes.Tuple(parent=obj)
            elem.postinit((key, value))
            elems.append(elem)
        obj.postinit(elts=elems)

        # pylint: disable=import-outside-toplevel; circular import
        from astroid import objects

        obj = objects.DictItems(obj)
        return self._generic_dict_attribute(obj, "items")

    @property
    def attr_keys(self):
        keys = [key for (key, _) in self._instance.items]
        obj = node_classes.List(parent=self._instance)
        obj.postinit(elts=keys)

        # pylint: disable=import-outside-toplevel; circular import
        from astroid import objects

        obj = objects.DictKeys(obj)
        return self._generic_dict_attribute(obj, "keys")

    @property
    def attr_values(self):

        values = [value for (_, value) in self._instance.items]
        obj = node_classes.List(parent=self._instance)
        obj.postinit(values)

        # pylint: disable=import-outside-toplevel; circular import
        from astroid import objects

        obj = objects.DictValues(obj)
        return self._generic_dict_attribute(obj, "values")