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Enable importlib.metadata backend on Python 3.11
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uranusjr committed May 10, 2022
1 parent e195f7b commit bd9bcef
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Showing 3 changed files with 34 additions and 3 deletions.
4 changes: 2 additions & 2 deletions .github/workflows/ci.yml
Original file line number Diff line number Diff line change
Expand Up @@ -219,11 +219,12 @@ jobs:
env:
TEMP: "R:\\Temp"

# TODO: Remove this when we add Python 3.11 to CI.
tests-importlib-metadata:
name: tests for importlib.metadata backend
runs-on: ubuntu-latest
env:
_PIP_METADATA_BACKEND_IMPORTLIB: egg-compat
_PIP_USE_IMPORTLIB_METADATA: 'true'

needs: [pre-commit, packaging, determine-changes]
if: >-
Expand All @@ -241,7 +242,6 @@ jobs:

- run: pip install nox 'virtualenv<20'

# Main check
- name: Run unit tests
run: >-
nox -s test-3.10 --
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4 changes: 4 additions & 0 deletions news/11044.process.rst
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@@ -0,0 +1,4 @@
Enable the ``importlib.metadata`` metadata implementation by default on
Python 3.11 (or later). The environment variable ``_PIP_USE_IMPORTLIB_METADATA``
can still be used to enable the implementation on 3.10 and earlier, or disable
it on 3.11 (by setting it to ``0`` or ``false``).
29 changes: 28 additions & 1 deletion src/pip/_internal/metadata/__init__.py
Original file line number Diff line number Diff line change
@@ -1,7 +1,11 @@
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:
Expand All @@ -22,14 +26,37 @@
]


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_resourcess`` otherwise. This can be overriden 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):
Distribution: Type[BaseDistribution]
Environment: Type[BaseEnvironment]


@functools.lru_cache(maxsize=None)
def select_backend() -> Backend:
if os.environ.get("_PIP_METADATA_BACKEND_IMPORTLIB"):
if _should_use_importlib_metadata():
from . import importlib

return cast(Backend, importlib)
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