Fix metadata handling for py38 and py39 venv environments

importlib.metadata in Python 3.10 had improved handling of certain
virtual environments. This change addresses the issue with some venv
environments not returning a version string for AnyIO.

Author: Stealthii

asyncer/_compat.py

@@ -1,14 +1,18 @@
 # AnyIO 4.1.0 renamed cancellable to abandon_on_cancel
-import importlib
-import importlib.metadata
+import sys
 from typing import Callable, TypeVar, Union
 
 import anyio
 import anyio.to_thread
 from anyio import CapacityLimiter
 from typing_extensions import TypeVarTuple, Unpack
 
-ANYIO_VERSION = importlib.metadata.version("anyio")
+if sys.version_info < (3, 10):
+    from importlib_metadata import version as get_version
+else:
+    from importlib.metadata import version as get_version
+
+ANYIO_VERSION = get_version("anyio")
 
 T_Retval = TypeVar("T_Retval")
 PosArgsT = TypeVarTuple("PosArgsT")

pyproject.toml

@@ -32,7 +32,8 @@ classifiers = [
 ]
 dependencies = [
     "anyio >=3.4.0,<5.0",
-    "typing_extensions >=4.8.0; python_version < '3.10'"
+    "importlib-metadata >=4.6; python_version < '3.10'",
+    "typing_extensions >=4.8.0; python_version < '3.10'",
 ]
 
 [project.urls]