Replace most pkg_resources calls with importlib.metadata and packaging

pkg_resources is deprecated and, under some circumstances, causes import
errors in Python 3.12. This commit replaces the deprecated pkg_resources
functions that access distribution metadata with calls to corresponding
functions from importlib.metadata (or its backport importlib_metadata)
and packaging. This change will bring pyinfra more in line with modern
recommendations and should resolve the errors.

The change introduces a new dependency on importlib_metadata in Python
versions prior to 3.10. Even though importlib.metadata was available in
Python 3.8, its entry_points() function did not have the group keyword
argument until 3.10, hence this commit prefers the backport until that
Python version.

The only remaining use of pkg_resources is the require() function, which
will take more work to replace since there's no ready equivalent in any
of the importlib* or packaging modules.

pyinfra/api/config.py

@@ -1,8 +1,9 @@
 from os import path
 from typing import Optional
 
-# TODO: move to importlib.resources
-from pkg_resources import Requirement, ResolutionError, parse_version, require
+from pkg_resources import ResolutionError, require
+from packaging.specifiers import SpecifierSet
+from packaging.version import Version
 
 from pyinfra import __version__, state
 
@@ -53,10 +54,10 @@ class ConfigDefaults:
 def check_pyinfra_version(version: str):
     if not version:
         return
-    running_version = parse_version(__version__)
-    required_versions = Requirement.parse("pyinfra{0}".format(version))
+    running_version = Version(__version__)
+    required_versions = SpecifierSet(version)
 
-    if running_version not in required_versions:  # type: ignore[operator]
+    if running_version not in required_versions:
         raise PyinfraError(
             f"pyinfra version requirement not met (requires {version}, running {__version__})"
         )

pyinfra/api/connectors.py

@@ -1,4 +1,7 @@
-import pkg_resources
+try:
+    from importlib_metadata import entry_points
+except ImportError:
+    from importlib.metadata import entry_points
 
 
 def _load_connector(entrypoint):
@@ -8,7 +11,7 @@ def _load_connector(entrypoint):
 def get_all_connectors():
     return {
         entrypoint.name: _load_connector(entrypoint)
-        for entrypoint in pkg_resources.iter_entry_points("pyinfra.connectors")
+        for entrypoint in entry_points(group="pyinfra.connectors")
     }
 
 

pyinfra/version.py

@@ -1,6 +1,9 @@
 try:
-    from pkg_resources import get_distribution
+    try:
+        from importlib_metadata import version
+    except ImportError:
+        from importlib.metadata import version
 
-    __version__ = get_distribution("pyinfra").version
+    __version__ = version("pyinfra")
 except Exception:
     __version__ = "unknown"

setup.py

@@ -29,10 +29,13 @@
     "pywinrm",
     "typeguard",
     "distro>=1.6,<2",
+    "packaging>=16.1",
     # Backport of graphlib used for DAG operation ordering
     'graphlib_backport ; python_version < "3.9"',
     # Backport of typing for Unpack (added 3.11)
     'typing-extensions ; python_version < "3.11"',
+    # Backport of importlib.metadata for entry_points(group=...) (added 3.10)
+    'importlib_metadata>=3.6 ; python_version < "3.10"',
 )
 
 TEST_REQUIRES = (