source/attr/_compat.py

# SPDX-License-Identifier: MIT

import inspect
import platform
import sys
import threading

from collections.abc import Mapping, Sequence  # noqa: F401
from typing import _GenericAlias


PYPY = platform.python_implementation() == "PyPy"
PY_3_10_PLUS = sys.version_info[:2] >= (3, 10)
PY_3_11_PLUS = sys.version_info[:2] >= (3, 11)
PY_3_12_PLUS = sys.version_info[:2] >= (3, 12)
PY_3_13_PLUS = sys.version_info[:2] >= (3, 13)
PY_3_14_PLUS = sys.version_info[:2] >= (3, 14)


if PY_3_14_PLUS:
    import annotationlib

    # We request forward-ref annotations to not break in the presence of
    # forward references.

    def _get_annotations(cls):
        return annotationlib.get_annotations(
            cls, format=annotationlib.Format.FORWARDREF
        )

else:

    def _get_annotations(cls):
        """
        Get annotations for *cls*.
        """
        return cls.__dict__.get("__annotations__", {})


class _AnnotationExtractor:
    """
    Extract type annotations from a callable, returning None whenever there
    is none.
    """

    __slots__ = ["sig"]

    def __init__(self, callable):
        try:
            self.sig = inspect.signature(callable)
        except (ValueError, TypeError):  # inspect failed
            self.sig = None

    def get_first_param_type(self):
        """
        Return the type annotation of the first argument if it's not empty.
        """
        if not self.sig:
            return None

        params = list(self.sig.parameters.values())
        if params and params[0].annotation is not inspect.Parameter.empty:
            return params[0].annotation

        return None

    def get_return_type(self):
        """
        Return the return type if it's not empty.
        """
        if (
            self.sig
            and self.sig.return_annotation is not inspect.Signature.empty
        ):
            return self.sig.return_annotation

        return None


# Thread-local global to track attrs instances which are already being repr'd.
# This is needed because there is no other (thread-safe) way to pass info
# about the instances that are already being repr'd through the call stack
# in order to ensure we don't perform infinite recursion.
#
# For instance, if an instance contains a dict which contains that instance,
# we need to know that we're already repr'ing the outside instance from within
# the dict's repr() call.
#
# This lives here rather than in _make.py so that the functions in _make.py
# don't have a direct reference to the thread-local in their globals dict.
# If they have such a reference, it breaks cloudpickle.
repr_context = threading.local()


def get_generic_base(cl):
    """If this is a generic class (A[str]), return the generic base for it."""
    if cl.__class__ is _GenericAlias:
        return cl.__origin__
    return None