Create the slotted class before generating methods

Author: aisk

Lib/dataclasses.py

@@ -561,8 +561,7 @@ def __annotate__(format, /):
             case _:
                 raise NotImplementedError(format)
 
-    # This is a flag for _add_slots to know it needs to regenerate this method
-    # In order to remove references to the original class when it is replaced
+    # Mark the function as generated by dataclasses, for introspection.
     __annotate__.__generated_by_dataclasses__ = True
     __annotate__.__qualname__ = f"{__class__.__qualname__}.{method_name}.__annotate__"
 
@@ -1118,6 +1117,16 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen,
     # also marks this class as being a dataclass.
     setattr(cls, _FIELDS, fields)
 
+    # It's an error to specify weakref_slot if slots is False.
+    if weakref_slot and not slots:
+        raise TypeError('weakref_slot is True but slots is False')
+    if slots:
+        # Create the slotted class before generating any methods, so that
+        # the generated methods are bound to the final class from the start
+        # and the __class__ cell fix-up in _add_slots only has to look at
+        # user-defined methods.
+        cls = _add_slots(cls, frozen, weakref_slot, fields)
+
     # Was this class defined with an explicit __hash__?  Note that if
     # __eq__ is defined in this class, then python will automatically
     # set __hash__ to None.  This is a heuristic, as it's possible
@@ -1235,12 +1244,6 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen,
         _set_new_attribute(cls, '__match_args__',
                            tuple(f.name for f in std_init_fields))
 
-    # It's an error to specify weakref_slot if slots is False.
-    if weakref_slot and not slots:
-        raise TypeError('weakref_slot is True but slots is False')
-    if slots:
-        cls = _add_slots(cls, frozen, weakref_slot, fields)
-
     abc.update_abstractmethods(cls)
 
     return cls
@@ -1284,23 +1287,6 @@ def _get_slots(cls):
             raise TypeError(f"Slots of '{cls.__name__}' cannot be determined")
 
 
-def _unwrap(func):
-    # A copy of `inspect.unwrap()`, to avoid importing `inspect` module.
-    # Keep this in sync with the original.
-    f = func  # remember the original func for error reporting
-    # Memoise by id to tolerate non-hashable objects, but store objects to
-    # ensure they aren't destroyed, which would allow their IDs to be reused.
-    memo = {id(f): f}
-    recursion_limit = sys.getrecursionlimit()
-    while not isinstance(func, type) and hasattr(func, '__wrapped__'):
-        func = func.__wrapped__
-        id_func = id(func)
-        if (id_func in memo) or (len(memo) >= recursion_limit):
-            raise ValueError(f'wrapper loop when unwrapping {f!r}')
-        memo[id_func] = func
-    return func
-
-
 def _update_func_cell_for__class__(f, oldcls, newcls):
     # Returns True if we update a cell, else False.
     if f is None:
@@ -1409,7 +1395,8 @@ def _add_slots(cls, is_frozen, weakref_slot, defined_fields):
 
         # If this is a wrapped function, unwrap it.
         if not isinstance(member, type) and hasattr(member, '__wrapped__'):
-            member = _unwrap(member)
+            import inspect
+            member = inspect.unwrap(member)
 
         if isinstance(member, types.FunctionType):
             if _update_func_cell_for__class__(member, cls, newcls):
@@ -1434,12 +1421,6 @@ def _add_slots(cls, is_frozen, weakref_slot, defined_fields):
         else:
             f.type = ann
 
-    # Fix the class reference in the __annotate__ method
-    init = newcls.__init__
-    if init_annotate := getattr(init, "__annotate__", None):
-        if getattr(init_annotate, "__generated_by_dataclasses__", False):
-            _update_func_cell_for__class__(init_annotate, cls, newcls)
-
     return newcls
 
 

Lib/test/test_dataclasses/__init__.py

@@ -43,6 +43,8 @@ def test_lazy_import(self):
 
     @cpython_only
     def test_slots_does_not_import_inspect(self):
+        # inspect is only needed to unwrap user-defined methods
+        # that are wrapped by a decorator.
         create_slotted_class = textwrap.dedent(
             """
             @dataclasses.dataclass(slots=True)