Issue #14605: Make explicit the entries on sys.path_hooks that used to

be implicit.

Added a warning for when sys.path_hooks is found to be empty. Also
changed the meaning of None in sys.path_importer_cache to represent
trying sys.path_hooks again (an interpretation of previous semantics).
Also added a warning for when None was found.

The long-term goal is for None in sys.path_importer_cache to represent
the same as imp.NullImporter: no finder found for that sys.path entry.

1 files changed, 5 insertions, 8 deletions

diff --git a/Lib/pkgutil.py b/Lib/pkgutil.py
index ef027be..932abbc 100644
--- a/Lib/pkgutil.py
+++ b/Lib/pkgutil.py
@@ -379,18 +379,15 @@ def get_importer(path_item):
         for path_hook in sys.path_hooks:
             try:
                 importer = path_hook(path_item)
+                sys.path_importer_cache.setdefault(path_item, importer)
                 break
             except ImportError:
                 pass
         else:
-            importer = None
-        sys.path_importer_cache.setdefault(path_item, importer)
-
-    if importer is None:
-        try:
-            importer = ImpImporter(path_item)
-        except ImportError:
-            importer = None
+            try:
+                importer = ImpImporter(path_item)
+            except ImportError:
+                importer = None
     return importer