Issue #23611: Serializing more "lookupable" objects (such as unbound methods

or nested classes) now are supported with pickle protocols < 4.

1 files changed, 18 insertions, 15 deletions

diff --git a/Lib/pickle.py b/Lib/pickle.py
index 67382ae..6c26c5e 100644
--- a/Lib/pickle.py
+++ b/Lib/pickle.py
@@ -258,24 +258,20 @@ class _Unframer:
 
 # Tools used for pickling.
 
-def _getattribute(obj, name, allow_qualname=False):
-    dotted_path = name.split(".")
-    if not allow_qualname and len(dotted_path) > 1:
-        raise AttributeError("Can't get qualified attribute {!r} on {!r}; " +
-                             "use protocols >= 4 to enable support"
-                             .format(name, obj))
-    for subpath in dotted_path:
+def _getattribute(obj, name):
+    for subpath in name.split('.'):
         if subpath == '<locals>':
             raise AttributeError("Can't get local attribute {!r} on {!r}"
                                  .format(name, obj))
         try:
+            parent = obj
             obj = getattr(obj, subpath)
         except AttributeError:
             raise AttributeError("Can't get attribute {!r} on {!r}"
                                  .format(name, obj))
-    return obj
+    return obj, parent
 
-def whichmodule(obj, name, allow_qualname=False):
+def whichmodule(obj, name):
     """Find the module an object belong to."""
     module_name = getattr(obj, '__module__', None)
     if module_name is not None:
@@ -286,7 +282,7 @@ def whichmodule(obj, name, allow_qualname=False):
         if module_name == '__main__' or module is None:
             continue
         try:
-            if _getattribute(module, name, allow_qualname) is obj:
+            if _getattribute(module, name)[0] is obj:
                 return module_name
         except AttributeError:
             pass
@@ -899,16 +895,16 @@ class _Pickler:
         write = self.write
         memo = self.memo
 
-        if name is None and self.proto >= 4:
+        if name is None:
             name = getattr(obj, '__qualname__', None)
         if name is None:
             name = obj.__name__
 
-        module_name = whichmodule(obj, name, allow_qualname=self.proto >= 4)
+        module_name = whichmodule(obj, name)
         try:
             __import__(module_name, level=0)
             module = sys.modules[module_name]
-            obj2 = _getattribute(module, name, allow_qualname=self.proto >= 4)
+            obj2, parent = _getattribute(module, name)
         except (ImportError, KeyError, AttributeError):
             raise PicklingError(
                 "Can't pickle %r: it's not found as %s.%s" %
@@ -930,11 +926,16 @@ class _Pickler:
                 else:
                     write(EXT4 + pack("<i", code))
                 return
+        lastname = name.rpartition('.')[2]
+        if parent is module:
+            name = lastname
         # Non-ASCII identifiers are supported only with protocols >= 3.
         if self.proto >= 4:
             self.save(module_name)
             self.save(name)
             write(STACK_GLOBAL)
+        elif parent is not module:
+            self.save_reduce(getattr, (parent, lastname))
         elif self.proto >= 3:
             write(GLOBAL + bytes(module_name, "utf-8") + b'\n' +
                   bytes(name, "utf-8") + b'\n')
@@ -1373,8 +1374,10 @@ class _Unpickler:
             elif module in _compat_pickle.IMPORT_MAPPING:
                 module = _compat_pickle.IMPORT_MAPPING[module]
         __import__(module, level=0)
-        return _getattribute(sys.modules[module], name,
-                             allow_qualname=self.proto >= 4)
+        if self.proto >= 4:
+            return _getattribute(sys.modules[module], name)[0]
+        else:
+            return getattr(sys.modules[module], name)
 
     def load_reduce(self):
         stack = self.stack