path: root/astroid/decorators.py

# 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

"""A few useful function/method decorators."""

from __future__ import annotations

import functools
import inspect
import sys
import warnings
from collections.abc import Callable, Generator
from typing import TypeVar

import wrapt

from astroid import _cache, util
from astroid.context import InferenceContext
from astroid.exceptions import InferenceError

if sys.version_info >= (3, 10):
    from typing import ParamSpec
else:
    from typing_extensions import ParamSpec

_R = TypeVar("_R")
_P = ParamSpec("_P")


@wrapt.decorator
def cached(func, instance, args, kwargs):
    """Simple decorator to cache result of method calls without args."""
    cache = getattr(instance, "__cache", None)
    if cache is None:
        instance.__cache = cache = {}
        _cache.CACHE_MANAGER.add_dict_cache(cache)
    try:
        return cache[func]
    except KeyError:
        cache[func] = result = func(*args, **kwargs)
        return result


# TODO: Remove when support for 3.7 is dropped
# TODO: astroid 3.0 -> move class behind sys.version_info < (3, 8) guard
class cachedproperty:
    """Provides a cached property equivalent to the stacking of
    @cached and @property, but more efficient.

    After first usage, the <property_name> becomes part of the object's
    __dict__. Doing:

      del obj.<property_name> empties the cache.

    Idea taken from the pyramid_ framework and the mercurial_ project.

    .. _pyramid: http://pypi.python.org/pypi/pyramid
    .. _mercurial: http://pypi.python.org/pypi/Mercurial
    """

    __slots__ = ("wrapped",)

    def __init__(self, wrapped):
        if sys.version_info >= (3, 8):
            warnings.warn(
                "cachedproperty has been deprecated and will be removed in astroid 3.0 for Python 3.8+. "
                "Use functools.cached_property instead.",
                DeprecationWarning,
            )
        try:
            wrapped.__name__
        except AttributeError as exc:
            raise TypeError(f"{wrapped} must have a __name__ attribute") from exc
        self.wrapped = wrapped

    @property
    def __doc__(self):
        doc = getattr(self.wrapped, "__doc__", None)
        return "<wrapped by the cachedproperty decorator>%s" % (
            "\n%s" % doc if doc else ""
        )

    def __get__(self, inst, objtype=None):
        if inst is None:
            return self
        val = self.wrapped(inst)
        setattr(inst, self.wrapped.__name__, val)
        return val


def path_wrapper(func):
    """Return the given infer function wrapped to handle the path.

    Used to stop inference if the node has already been looked
    at for a given `InferenceContext` to prevent infinite recursion
    """

    @functools.wraps(func)
    def wrapped(
        node, context: InferenceContext | None = None, _func=func, **kwargs
    ) -> Generator:
        """Wrapper function handling context."""
        if context is None:
            context = InferenceContext()
        if context.push(node):
            return

        yielded = set()

        for res in _func(node, context, **kwargs):
            # unproxy only true instance, not const, tuple, dict...
            if res.__class__.__name__ == "Instance":
                ares = res._proxied
            else:
                ares = res
            if ares not in yielded:
                yield res
                yielded.add(ares)

    return wrapped


@wrapt.decorator
def yes_if_nothing_inferred(func, instance, args, kwargs):
    generator = func(*args, **kwargs)

    try:
        yield next(generator)
    except StopIteration:
        # generator is empty
        yield util.Uninferable
        return

    yield from generator


@wrapt.decorator
def raise_if_nothing_inferred(func, instance, args, kwargs):
    generator = func(*args, **kwargs)
    try:
        yield next(generator)
    except StopIteration as error:
        # generator is empty
        if error.args:
            # pylint: disable=not-a-mapping
            raise InferenceError(**error.args[0]) from error
        raise InferenceError(
            "StopIteration raised without any error information."
        ) from error
    except RecursionError as error:
        raise InferenceError(
            f"RecursionError raised with limit {sys.getrecursionlimit()}."
        ) from error

    yield from generator


# Expensive decorators only used to emit Deprecation warnings.
# If no other than the default DeprecationWarning are enabled,
# fall back to passthrough implementations.
if util.check_warnings_filter():  # noqa: C901

    def deprecate_default_argument_values(
        astroid_version: str = "3.0", **arguments: str
    ) -> Callable[[Callable[_P, _R]], Callable[_P, _R]]:
        """Decorator which emits a DeprecationWarning if any arguments specified
        are None or not passed at all.

        Arguments should be a key-value mapping, with the key being the argument to check
        and the value being a type annotation as string for the value of the argument.

        To improve performance, only used when DeprecationWarnings other than
        the default one are enabled.
        """
        # Helpful links
        # Decorator for DeprecationWarning: https://stackoverflow.com/a/49802489
        # Typing of stacked decorators: https://stackoverflow.com/a/68290080

        def deco(func: Callable[_P, _R]) -> Callable[_P, _R]:
            """Decorator function."""

            @functools.wraps(func)
            def wrapper(*args: _P.args, **kwargs: _P.kwargs) -> _R:
                """Emit DeprecationWarnings if conditions are met."""

                keys = list(inspect.signature(func).parameters.keys())
                for arg, type_annotation in arguments.items():
                    try:
                        index = keys.index(arg)
                    except ValueError:
                        raise ValueError(
                            f"Can't find argument '{arg}' for '{args[0].__class__.__qualname__}'"
                        ) from None
                    if (
                        # Check kwargs
                        # - if found, check it's not None
                        (arg in kwargs and kwargs[arg] is None)
                        # Check args
                        # - make sure not in kwargs
                        # - len(args) needs to be long enough, if too short
                        #   arg can't be in args either
                        # - args[index] should not be None
                        or arg not in kwargs
                        and (
                            index == -1
                            or len(args) <= index
                            or (len(args) > index and args[index] is None)
                        )
                    ):
                        warnings.warn(
                            f"'{arg}' will be a required argument for "
                            f"'{args[0].__class__.__qualname__}.{func.__name__}'"
                            f" in astroid {astroid_version} "
                            f"('{arg}' should be of type: '{type_annotation}')",
                            DeprecationWarning,
                        )
                return func(*args, **kwargs)

            return wrapper

        return deco

    def deprecate_arguments(
        astroid_version: str = "3.0", **arguments: str
    ) -> Callable[[Callable[_P, _R]], Callable[_P, _R]]:
        """Decorator which emits a DeprecationWarning if any arguments specified
        are passed.

        Arguments should be a key-value mapping, with the key being the argument to check
        and the value being a string that explains what to do instead of passing the argument.

        To improve performance, only used when DeprecationWarnings other than
        the default one are enabled.
        """

        def deco(func: Callable[_P, _R]) -> Callable[_P, _R]:
            @functools.wraps(func)
            def wrapper(*args: _P.args, **kwargs: _P.kwargs) -> _R:
                keys = list(inspect.signature(func).parameters.keys())
                for arg, note in arguments.items():
                    try:
                        index = keys.index(arg)
                    except ValueError:
                        raise ValueError(
                            f"Can't find argument '{arg}' for '{args[0].__class__.__qualname__}'"
                        ) from None
                    if arg in kwargs or len(args) > index:
                        warnings.warn(
                            f"The argument '{arg}' for "
                            f"'{args[0].__class__.__qualname__}.{func.__name__}' is deprecated "
                            f"and will be removed in astroid {astroid_version} ({note})",
                            DeprecationWarning,
                        )
                return func(*args, **kwargs)

            return wrapper

        return deco

else:

    def deprecate_default_argument_values(
        astroid_version: str = "3.0", **arguments: str
    ) -> Callable[[Callable[_P, _R]], Callable[_P, _R]]:
        """Passthrough decorator to improve performance if DeprecationWarnings are
        disabled.
        """

        def deco(func: Callable[_P, _R]) -> Callable[_P, _R]:
            """Decorator function."""
            return func

        return deco

    def deprecate_arguments(
        astroid_version: str = "3.0", **arguments: str
    ) -> Callable[[Callable[_P, _R]], Callable[_P, _R]]:
        """Passthrough decorator to improve performance if DeprecationWarnings are
        disabled.
        """

        def deco(func: Callable[_P, _R]) -> Callable[_P, _R]:
            """Decorator function."""
            return func

        return deco