Issue #25791: Raise an ImportWarning when __spec__ or __package__ are

not defined for a relative import.

This is the start of work to try and clean up import semantics to rely
more on a module's spec than on the myriad attributes that get set on
a module. Thanks to Rose Ames for the patch.

1 files changed, 6 insertions, 0 deletions

diff --git a/Lib/importlib/_bootstrap.py b/Lib/importlib/_bootstrap.py
index 6f62bb3..9adcf7b 100644
--- a/Lib/importlib/_bootstrap.py
+++ b/Lib/importlib/_bootstrap.py
@@ -1032,8 +1032,14 @@ def _calc___package__(globals):
     to represent that its proper value is unknown.
 
     """
+    spec = globals.get('__spec__')
+    if spec is not None:
+        return spec.parent
     package = globals.get('__package__')
     if package is None:
+        _warnings.warn("can't resolve package from __spec__ or __package__, "
+                       "falling back on __name__ and __path__",
+                       ImportWarning, stacklevel=3)
         package = globals['__name__']
         if '__path__' not in globals:
             package = package.rpartition('.')[0]