bpo-35673: Add a public alias for namespace package __loader__ attribute (#29049)

Rename namespace package __loader__ class to be public.

Make the old name, i.e. _NamespaceLoader, an alias for the public name, for backward compatibility.

1 files changed, 9 insertions, 3 deletions

diff --git a/Lib/importlib/_bootstrap_external.py b/Lib/importlib/_bootstrap_external.py
index c9692b542a5..ef4f23a4b49 100644
--- a/Lib/importlib/_bootstrap_external.py
+++ b/Lib/importlib/_bootstrap_external.py
@@ -1279,8 +1279,10 @@ class _NamespacePath:
         self._path.append(item)
 
 
-# We use this exclusively in module_from_spec() for backward-compatibility.
-class _NamespaceLoader:
+# This class is actually exposed publicly in a namespace package's __loader__
+# attribute, so it should be available through a non-private name.
+# https://bugs.python.org/issue35673
+class NamespaceLoader:
     def __init__(self, name, path, path_finder):
         self._path = _NamespacePath(name, path, path_finder)
 
@@ -1291,7 +1293,7 @@ class _NamespaceLoader:
         The method is deprecated.  The import machinery does the job itself.
 
         """
-        _warnings.warn("_NamespaceLoader.module_repr() is deprecated and "
+        _warnings.warn("NamespaceLoader.module_repr() is deprecated and "
                        "slated for removal in Python 3.12", DeprecationWarning)
         return '<module {!r} (namespace)>'.format(module.__name__)
 
@@ -1327,6 +1329,10 @@ class _NamespaceLoader:
         return NamespaceReader(self._path)
 
 
+# We use this exclusively in module_from_spec() for backward-compatibility.
+_NamespaceLoader = NamespaceLoader
+
+
 # Finders #####################################################################
 
 class PathFinder: