Replace setattr and getattr calls with __dict__ manipulations (#905)

- fixes problems with custom setattr__ implementations like pytorch

CHANGES.md

@@ -6,6 +6,8 @@ The released versions correspond to PyPI releases.
 ### Fixes
 * fixes the problem that filesystem patching was still active in the pytest
   logreport phase (see [#904](../../issues/904))
+* Restores compatibility with PyTorch 2.0 and above, as well as with other
+  classes that have custom __setattr__ methods (see [#905](../../pull/905)).
 
 ## [Version 5.3.0](https://pypi.python.org/pypi/pyfakefs/5.3.0) (2023-10-11)
 Adds official support for Python 3.12.

pyfakefs/mox3_stubout.py

@@ -61,22 +61,20 @@ def smart_set(self, obj, attr_name, new_attr):
         This method supports the case where attr_name is a staticmethod or a
         classmethod of obj.
 
-        Notes:
-          - If obj is an instance, then it is its class that will actually be
-            stubbed. Note that the method Set() does not do that: if obj is
-            an instance, it (and not its class) will be stubbed.
-          - The stubbing is using the builtin getattr and setattr. So, the
-            __get__ and __set__ will be called when stubbing (TODO: A better
-            idea would probably be to manipulate obj.__dict__ instead of
-            getattr() and setattr()).
+        If obj is an instance, then it is its class that will actually be
+        stubbed. Note that the method Set() does not do that: if obj is an
+        instance, it (and not its class) will be stubbed.
 
         Raises AttributeError if the attribute cannot be found.
         """
         if inspect.ismodule(obj) or (
             not inspect.isclass(obj) and attr_name in obj.__dict__
         ):
             orig_obj = obj
-            orig_attr = getattr(obj, attr_name)
+            if attr_name in obj.__dict__:
+                orig_attr = obj.__dict__[attr_name]
+            else:
+                orig_attr = None
 
         else:
             if not inspect.isclass(obj):
@@ -91,21 +89,15 @@ def smart_set(self, obj, attr_name, new_attr):
             for cls in mro:
                 try:
                     orig_obj = cls
-                    orig_attr = getattr(obj, attr_name)
-                except AttributeError:
+                    orig_attr = obj.__dict__[attr_name]
+                except KeyError:
                     continue
 
         if orig_attr is None:
             raise AttributeError("Attribute not found.")
 
-        # Calling getattr() on a staticmethod transforms it to a 'normal'
-        # function. We need to ensure that we put it back as a staticmethod.
-        old_attribute = obj.__dict__.get(attr_name)
-        if old_attribute is not None and isinstance(old_attribute, staticmethod):
-            orig_attr = staticmethod(orig_attr)  # pytype: disable=not-callable
-
         self.stubs.append((orig_obj, attr_name, orig_attr))
-        setattr(orig_obj, attr_name, new_attr)
+        orig_obj.__dict__[attr_name] = new_attr
 
     def smart_unset_all(self):
         """Reverses all the SmartSet() calls.
@@ -116,8 +108,8 @@ def smart_unset_all(self):
         """
         self.stubs.reverse()
 
-        for args in self.stubs:
-            setattr(*args)
+        for obj, attr_name, old_attr in self.stubs:
+            obj.__dict__[attr_name] = old_attr
 
         self.stubs = []
 
@@ -143,7 +135,7 @@ def set(self, parent, child_name, new_child):
                 old_child = classmethod(old_child.__func__)
 
         self.cache.append((parent, old_child, child_name))
-        setattr(parent, child_name, new_child)
+        parent.__dict__[child_name] = new_child
 
     def unset_all(self):
         """Reverses all the Set() calls.
@@ -158,5 +150,5 @@ def unset_all(self):
         self.cache.reverse()
 
         for parent, old_child, child_name in self.cache:
-            setattr(parent, child_name, old_child)
+            parent.__dict__[child_name] = old_child
         self.cache = []