Only enumerate extension entry points when required

docs/change_log/release-3.4.md

@@ -66,3 +66,5 @@ The following new features have been included in the 3.4 release:
 ## Bug fixes
 
 The following bug fixes are included in the 3.4 release:
+
+* Extension entry-points are only loaded if needed (#1216).

markdown/core.py

@@ -150,7 +150,7 @@ def build_extension(self, ext_name, configs):
         """
         configs = dict(configs)
 
-        entry_points = [ep for ep in util.INSTALLED_EXTENSIONS if ep.name == ext_name]
+        entry_points = [ep for ep in util.get_installed_extensions() if ep.name == ext_name]
         if entry_points:
             ext = entry_points[0].load()
             return ext(**configs)

markdown/util.py

@@ -24,17 +24,11 @@
 import warnings
 import xml.etree.ElementTree
 from collections import namedtuple
-from functools import wraps
+from functools import wraps, lru_cache
 from itertools import count
 
 from .pep562 import Pep562
 
-if sys.version_info >= (3, 10):
-    from importlib import metadata
-else:
-    # <PY310 use backport
-    import importlib_metadata as metadata
-
 PY37 = (3, 7) <= sys.version_info
 
 
@@ -84,8 +78,6 @@
 -----------------------------------------------------------------------------
 """
 
-# Only load extension entry_points once.
-INSTALLED_EXTENSIONS = metadata.entry_points(group='markdown.extensions')
 RTL_BIDI_RANGES = (
     ('\u0590', '\u07FF'),
     # Hebrew (0590-05FF), Arabic (0600-06FF),
@@ -101,6 +93,16 @@
 """
 
 
+@lru_cache(maxsize=None)
+def get_installed_extensions():
+    if sys.version_info >= (3, 10):
+        from importlib import metadata
+    else:  # <PY310 use backport
+        import importlib_metadata as metadata
+    # Only load extension entry_points once.
+    return metadata.entry_points(group='markdown.extensions')
+
+
 def deprecated(message, stacklevel=2):
     """
     Raise a DeprecationWarning when wrapped function/method is called.