glad: improves importlib.metadata fallbacks

No more checks for importlib_metadata backports,
if you have to install a backport you can also install setuptools.

glad/plugin.py

@@ -2,32 +2,22 @@
 import logging
 import inspect
 try:
-    from importlib.metadata import entry_points as imp_entry_points
-    ENTRY_POINTS = 'importlib'
+    from importlib.metadata import entry_points
+
+    if sys.version_info < (3, 10):
+        _entry_points = entry_points
+
+        def entry_points(group=None):
+            return _entry_points()[group]
 except ImportError:
-    try:
-        from importlib_metadata import entry_points as imp_entry_points
-        ENTRY_POINTS = 'importlib'
-    except ImportError:
-        from pkg_resources import iter_entry_points
-        ENTRY_POINTS = 'pkg_resources'
+    from pkg_resources import iter_entry_points as entry_points
 
 import glad.specification
 from glad.generator.c import CGenerator
 from glad.generator.rust import RustGenerator
 from glad.parse import Specification
 
 
-def _entry_points(group=None):
-    if ENTRY_POINTS == 'importlib':
-        if sys.version_info < (3, 10):
-            return imp_entry_points()[group]
-        else:
-            return imp_entry_points(group=group)
-    else:
-        return iter_entry_points(group=group, name=None)
-
-
 logger = logging.getLogger(__name__)
 
 
@@ -49,7 +39,7 @@ def _entry_points(group=None):
 def find_generators(default=None, entry_point=GENERATOR_ENTRY_POINT):
     generators = dict(DEFAULT_GENERATORS if default is None else default)
 
-    for entry_point in _entry_points(group=entry_point):
+    for entry_point in entry_points(group=entry_point):
         generators[entry_point.name] = entry_point.load()
         logger.debug('loaded language %s: %s', entry_point.name, generators[entry_point.name])
 
@@ -59,7 +49,7 @@ def find_generators(default=None, entry_point=GENERATOR_ENTRY_POINT):
 def find_specifications(default=None, entry_point=SPECIFICATION_ENTRY_POINT):
     specifications = dict(DEFAULT_SPECIFICATIONS if default is None else default)
 
-    for entry_point in _entry_points(group=entry_point):
+    for entry_point in entry_points(group=entry_point):
         specifications[entry_point.name] = entry_point.load()
         logger.debug('loaded specification %s: %s', entry_point.name, specifications[entry_point.name])