bpo-34776: Fix dataclasses to support __future__ "annotations" mode (#9518)

Author: 1st1

Lib/dataclasses.py

@@ -378,23 +378,24 @@ def _create_fn(name, args, body, *, globals=None, locals=None,
  # worries about external callers.
  if locals is None:
  locals = {}
- # __builtins__ may be the "builtins" module or
- # the value of its "__dict__",
- # so make sure "__builtins__" is the module.
- if globals is not None and '__builtins__' not in globals:
- globals['__builtins__'] = builtins
+ if 'BUILTINS' not in locals:
+ locals['BUILTINS'] = builtins
  return_annotation = ''
  if return_type is not MISSING:
  locals['_return_type'] = return_type
  return_annotation = '->_return_type'
  args = ','.join(args)
- body = '\n'.join(f' {b}' for b in body)
+ body = '\n'.join(f'  {b}' for b in body)
 
  # Compute the text of the entire function.
- txt = f'def {name}({args}){return_annotation}:\n{body}'
+ txt = f' def {name}({args}){return_annotation}:\n{body}'
 
- exec(txt, globals, locals)
- return locals[name]
+ local_vars = ', '.join(locals.keys())
+ txt = f"def __create_fn__({local_vars}):\n{txt}\n return {name}"
+
+ ns = {}
+ exec(txt, globals, ns)
+ return ns['__create_fn__'](**locals)
 
 
 def _field_assign(frozen, name, value, self_name):
@@ -405,7 +406,7 @@ def _field_assign(frozen, name, value, self_name):
  # self_name is what "self" is called in this function: don't
  # hard-code "self", since that might be a field name.
  if frozen:
- return f'__builtins__.object.__setattr__({self_name},{name!r},{value})'
+ return f'BUILTINS.object.__setattr__({self_name},{name!r},{value})'
  return f'{self_name}.{name}={value}'
 
 
@@ -482,7 +483,7 @@ def _init_param(f):
  return f'{f.name}:_type_{f.name}{default}'
 
 
-def _init_fn(fields, frozen, has_post_init, self_name):
+def _init_fn(fields, frozen, has_post_init, self_name, globals):
  # fields contains both real fields and InitVar pseudo-fields.
 
  # Make sure we don't have fields without defaults following fields
@@ -500,12 +501,15 @@ def _init_fn(fields, frozen, has_post_init, self_name):
  raise TypeError(f'non-default argument {f.name!r} '
  'follows default argument')
 
- globals = {'MISSING': MISSING,
- '_HAS_DEFAULT_FACTORY': _HAS_DEFAULT_FACTORY}
+ locals = {f'_type_{f.name}': f.type for f in fields}
+ locals.update({
+ 'MISSING': MISSING,
+ '_HAS_DEFAULT_FACTORY': _HAS_DEFAULT_FACTORY,
+ })
 
  body_lines = []
  for f in fields:
- line = _field_init(f, frozen, globals, self_name)
+ line = _field_init(f, frozen, locals, self_name)
  # line is None means that this field doesn't require
  # initialization (it's a pseudo-field). Just skip it.
  if line:
@@ -521,7 +525,6 @@ def _init_fn(fields, frozen, has_post_init, self_name):
  if not body_lines:
  body_lines = ['pass']
 
- locals = {f'_type_{f.name}': f.type for f in fields}
  return _create_fn('__init__',
  [self_name] + [_init_param(f) for f in fields if f.init],
  body_lines,
@@ -530,20 +533,19 @@ def _init_fn(fields, frozen, has_post_init, self_name):
  return_type=None)
 
 
-def _repr_fn(fields):
+def _repr_fn(fields, globals):
  fn = _create_fn('__repr__',
  ('self',),
  ['return self.__class__.__qualname__ + f"(' +
  ', '.join([f"{f.name}={{self.{f.name}!r}}"
  for f in fields]) +
- ')"'])
+ ')"'],
+ globals=globals)
  return _recursive_repr(fn)
 
 
-def _frozen_get_del_attr(cls, fields):
- # XXX: globals is modified on the first call to _create_fn, then
- # the modified version is used in the second call. Is this okay?
- globals = {'cls': cls,
+def _frozen_get_del_attr(cls, fields, globals):
+ locals = {'cls': cls,
  'FrozenInstanceError': FrozenInstanceError}
  if fields:
  fields_str = '(' + ','.join(repr(f.name) for f in fields) + ',)'
@@ -555,17 +557,19 @@ def _frozen_get_del_attr(cls, fields):
  (f'if type(self) is cls or name in {fields_str}:',
  ' raise FrozenInstanceError(f"cannot assign to field {name!r}")',
  f'super(cls, self).__setattr__(name, value)'),
+ locals=locals,
  globals=globals),
  _create_fn('__delattr__',
  ('self', 'name'),
  (f'if type(self) is cls or name in {fields_str}:',
  ' raise FrozenInstanceError(f"cannot delete field {name!r}")',
  f'super(cls, self).__delattr__(name)'),
+ locals=locals,
  globals=globals),
  )
 
 
-def _cmp_fn(name, op, self_tuple, other_tuple):
+def _cmp_fn(name, op, self_tuple, other_tuple, globals):
  # Create a comparison function. If the fields in the object are
  # named 'x' and 'y', then self_tuple is the string
  # '(self.x,self.y)' and other_tuple is the string
@@ -575,14 +579,16 @@ def _cmp_fn(name, op, self_tuple, other_tuple):
  ('self', 'other'),
  [ 'if other.__class__ is self.__class__:',
  f' return {self_tuple}{op}{other_tuple}',
- 'return NotImplemented'])
+ 'return NotImplemented'],
+ globals=globals)
 
 
-def _hash_fn(fields):
+def _hash_fn(fields, globals):
  self_tuple = _tuple_str('self', fields)
  return _create_fn('__hash__',
  ('self',),
- [f'return hash({self_tuple})'])
+ [f'return hash({self_tuple})'],
+ globals=globals)
 
 
 def _is_classvar(a_type, typing):
@@ -755,14 +761,14 @@ def _set_new_attribute(cls, name, value):
 # take. The common case is to do nothing, so instead of providing a
 # function that is a no-op, use None to signify that.
 
-def _hash_set_none(cls, fields):
+def _hash_set_none(cls, fields, globals):
  return None
 
-def _hash_add(cls, fields):
+def _hash_add(cls, fields, globals):
  flds = [f for f in fields if (f.compare if f.hash is None else f.hash)]
- return _hash_fn(flds)
+ return _hash_fn(flds, globals)
 
-def _hash_exception(cls, fields):
+def _hash_exception(cls, fields, globals):
  # Raise an exception.
  raise TypeError(f'Cannot overwrite attribute __hash__ '
  f'in class {cls.__name__}')
@@ -804,6 +810,16 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen):
  # is defined by the base class, which is found first.
  fields = {}
 
+ if cls.__module__ in sys.modules:
+ globals = sys.modules[cls.__module__].__dict__
+ else:
+ # Theoretically this can happen if someone writes
+ # a custom string to cls.__module__. In which case
+ # such dataclass won't be fully introspectable
+ # (w.r.t. typing.get_type_hints) but will still function
+ # correctly.
+ globals = {}
+
  setattr(cls, _PARAMS, _DataclassParams(init, repr, eq, order,
  unsafe_hash, frozen))
 
@@ -913,6 +929,7 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen):
  # if possible.
  '__dataclass_self__' if 'self' in fields
  else 'self',
+ globals,
  ))
 
  # Get the fields as a list, and include only real fields. This is
@@ -921,7 +938,7 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen):
 
  if repr:
  flds = [f for f in field_list if f.repr]
- _set_new_attribute(cls, '__repr__', _repr_fn(flds))
+ _set_new_attribute(cls, '__repr__', _repr_fn(flds, globals))
 
  if eq:
  # Create _eq__ method. There's no need for a __ne__ method,
@@ -931,7 +948,8 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen):
  other_tuple = _tuple_str('other', flds)
  _set_new_attribute(cls, '__eq__',
  _cmp_fn('__eq__', '==',
- self_tuple, other_tuple))
+ self_tuple, other_tuple,
+ globals=globals))
 
  if order:
  # Create and set the ordering methods.
@@ -944,13 +962,14 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen):
  ('__ge__', '>='),
  ]:
  if _set_new_attribute(cls, name,
- _cmp_fn(name, op, self_tuple, other_tuple)):
+ _cmp_fn(name, op, self_tuple, other_tuple,
+ globals=globals)):
  raise TypeError(f'Cannot overwrite attribute {name} '
  f'in class {cls.__name__}. Consider using '
  'functools.total_ordering')
 
  if frozen:
- for fn in _frozen_get_del_attr(cls, field_list):
+ for fn in _frozen_get_del_attr(cls, field_list, globals):
  if _set_new_attribute(cls, fn.__name__, fn):
  raise TypeError(f'Cannot overwrite attribute {fn.__name__} '
  f'in class {cls.__name__}')
@@ -963,7 +982,7 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen):
  if hash_action:
  # No need to call _set_new_attribute here, since by the time
  # we're here the overwriting is unconditional.
- cls.__hash__ = hash_action(cls, field_list)
+ cls.__hash__ = hash_action(cls, field_list, globals)
 
  if not getattr(cls, '__doc__'):
  # Create a class doc-string.

Lib/test/dataclass_textanno.py

@@ -0,0 +1,12 @@
+from __future__ import annotations
+
+import dataclasses
+
+
+class Foo:
+ pass
+
+
+@dataclasses.dataclass
+class Bar:
+ foo: Foo

Lib/test/test_dataclasses.py

@@ -10,6 +10,7 @@
 import unittest
 from unittest.mock import Mock
 from typing import ClassVar, Any, List, Union, Tuple, Dict, Generic, TypeVar, Optional
+from typing import get_type_hints
 from collections import deque, OrderedDict, namedtuple
 from functools import total_ordering
 
@@ -2926,6 +2927,17 @@ def test_classvar_module_level_import(self):
  # won't exist on the instance.
  self.assertNotIn('not_iv4', c.__dict__)
 
+ def test_text_annotations(self):
+ from test import dataclass_textanno
+
+ self.assertEqual(
+ get_type_hints(dataclass_textanno.Bar),
+ {'foo': dataclass_textanno.Foo})
+ self.assertEqual(
+ get_type_hints(dataclass_textanno.Bar.__init__),
+ {'foo': dataclass_textanno.Foo,
+ 'return': type(None)})
+
 
 class TestMakeDataclass(unittest.TestCase):
  def test_simple(self):

Misc/NEWS.d/next/Library/2018-09-23-14-24-37.bpo-34776.1SrQe3.rst

@@ -0,0 +1 @@
+Fix dataclasses to support forward references in type annotations