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import contextlib
import functools
import os
import sys
from typing import TYPE_CHECKING, List, Optional, Type, cast
from pip._internal.utils.misc import strtobool
from .base import BaseDistribution, BaseEnvironment, FilesystemWheel, MemoryWheel, Wheel
if TYPE_CHECKING:
from typing import Literal, Protocol
else:
Protocol = object
__all__ = [
"BaseDistribution",
"BaseEnvironment",
"FilesystemWheel",
"MemoryWheel",
"Wheel",
"get_default_environment",
"get_environment",
"get_wheel_distribution",
"select_backend",
]
def _should_use_importlib_metadata() -> bool:
"""Whether to use the ``importlib.metadata`` or ``pkg_resources`` backend.
By default, pip uses ``importlib.metadata`` on Python 3.11+, and
``pkg_resources`` otherwise. This can be overridden by a couple of ways:
* If environment variable ``_PIP_USE_IMPORTLIB_METADATA`` is set, it
dictates whether ``importlib.metadata`` is used, regardless of Python
version.
* On Python 3.11+, Python distributors can patch ``importlib.metadata``
to add a global constant ``_PIP_USE_IMPORTLIB_METADATA = False``. This
makes pip use ``pkg_resources`` (unless the user set the aforementioned
environment variable to *True*).
"""
with contextlib.suppress(KeyError, ValueError):
return bool(strtobool(os.environ["_PIP_USE_IMPORTLIB_METADATA"]))
if sys.version_info < (3, 11):
return False
import importlib.metadata
return bool(getattr(importlib.metadata, "_PIP_USE_IMPORTLIB_METADATA", True))
class Backend(Protocol):
NAME: 'Literal["importlib", "pkg_resources"]'
Distribution: Type[BaseDistribution]
Environment: Type[BaseEnvironment]
@functools.lru_cache(maxsize=None)
def select_backend() -> Backend:
if _should_use_importlib_metadata():
from . import importlib
return cast(Backend, importlib)
from . import pkg_resources
return cast(Backend, pkg_resources)
def get_default_environment() -> BaseEnvironment:
"""Get the default representation for the current environment.
This returns an Environment instance from the chosen backend. The default
Environment instance should be built from ``sys.path`` and may use caching
to share instance state across calls.
"""
return select_backend().Environment.default()
def get_environment(paths: Optional[List[str]]) -> BaseEnvironment:
"""Get a representation of the environment specified by ``paths``.
This returns an Environment instance from the chosen backend based on the
given import paths. The backend must build a fresh instance representing
the state of installed distributions when this function is called.
"""
return select_backend().Environment.from_paths(paths)
def get_directory_distribution(directory: str) -> BaseDistribution:
"""Get the distribution metadata representation in the specified directory.
This returns a Distribution instance from the chosen backend based on
the given on-disk ``.dist-info`` directory.
"""
return select_backend().Distribution.from_directory(directory)
def get_wheel_distribution(wheel: Wheel, canonical_name: str) -> BaseDistribution:
"""Get the representation of the specified wheel's distribution metadata.
This returns a Distribution instance from the chosen backend based on
the given wheel's ``.dist-info`` directory.
:param canonical_name: Normalized project name of the given wheel.
"""
return select_backend().Distribution.from_wheel(wheel, canonical_name)
def get_metadata_distribution(
metadata_contents: bytes,
filename: str,
canonical_name: str,
) -> BaseDistribution:
"""Get the dist representation of the specified METADATA file contents.
This returns a Distribution instance from the chosen backend sourced from the data
in `metadata_contents`.
:param metadata_contents: Contents of a METADATA file within a dist, or one served
via PEP 658.
:param filename: Filename for the dist this metadata represents.
:param canonical_name: Normalized project name of the given dist.
"""
return select_backend().Distribution.from_metadata_file_contents(
metadata_contents,
filename,
canonical_name,
)
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