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Merged
youknowone merged 1 commit into from
May 12, 2026
+136 −60
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Update dataclasses.py to 3.14.5 #7857

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26 changes: 17 additions & 9 deletions Lib/dataclasses.py
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Original file line number Diff line number Diff line change
Expand Up @@ -725,25 +725,25 @@ def _init_fn(fields, std_fields, kw_only_fields, frozen, has_post_init,
annotation_fields=annotation_fields)


def _frozen_get_del_attr(cls, fields, func_builder):
locals = {'cls': cls,
def _frozen_set_del_attr(cls, fields, func_builder):
locals = {'__class__': cls,
'FrozenInstanceError': FrozenInstanceError}
condition = 'type(self) is cls'
condition = 'type(self) is __class__'
if fields:
condition += ' or name in {' + ', '.join(repr(f.name) for f in fields) + '}'

func_builder.add_fn('__setattr__',
('self', 'name', 'value'),
(f' if {condition}:',
' raise FrozenInstanceError(f"cannot assign to field {name!r}")',
f' super(cls, self).__setattr__(name, value)'),
f' super(__class__, self).__setattr__(name, value)'),
locals=locals,
overwrite_error=True)
func_builder.add_fn('__delattr__',
('self', 'name'),
(f' if {condition}:',
' raise FrozenInstanceError(f"cannot delete field {name!r}")',
f' super(cls, self).__delattr__(name)'),
f' super(__class__, self).__delattr__(name)'),
locals=locals,
overwrite_error=True)

Expand Down Expand Up @@ -1199,7 +1199,7 @@ def _process_class(cls, init, repr, eq, order, unsafe_hash, frozen,
overwrite_error='Consider using functools.total_ordering')

if frozen:
_frozen_get_del_attr(cls, field_list, func_builder)
_frozen_set_del_attr(cls, field_list, func_builder)

# Decide if/how we're going to create a hash function.
hash_action = _hash_action[bool(unsafe_hash),
Expand Down Expand Up @@ -1292,10 +1292,18 @@ def _update_func_cell_for__class__(f, oldcls, newcls):
# This function doesn't reference __class__, so nothing to do.
return False
# Fix the cell to point to the new class, if it's already pointing
# at the old class. I'm not convinced that the "is oldcls" test
# is needed, but other than performance can't hurt.
# at the old class.
closure = f.__closure__[idx]
if closure.cell_contents is oldcls:

try:
contents = closure.cell_contents
except ValueError:
# Cell is empty
return False

# This check makes it so we avoid updating an incorrect cell if the
# class body contains a function that was defined in a different class.
if contents is oldcls:
closure.cell_contents = newcls
return True
return False
Expand Down
170 changes: 119 additions & 51 deletions Lib/test/test_dataclasses/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3054,29 +3054,41 @@ class C(base):


class TestFrozen(unittest.TestCase):
# Some tests have a subtest with a slotted dataclass.
# See https://github.com/python/cpython/issues/105936 for the reasons.

def test_frozen(self):
@dataclass(frozen=True)
class C:
i: int
for slots in (False, True):
with self.subTest(slots=slots):

c = C(10)
self.assertEqual(c.i, 10)
with self.assertRaises(FrozenInstanceError):
c.i = 5
self.assertEqual(c.i, 10)
@dataclass(frozen=True, slots=slots)
class C:
i: int

c = C(10)
self.assertEqual(c.i, 10)
with self.assertRaises(FrozenInstanceError):
c.i = 5
self.assertEqual(c.i, 10)
with self.assertRaises(FrozenInstanceError):
del c.i
self.assertEqual(c.i, 10)

def test_frozen_empty(self):
@dataclass(frozen=True)
class C:
pass
for slots in (False, True):
with self.subTest(slots=slots):

c = C()
self.assertNotHasAttr(c, 'i')
with self.assertRaises(FrozenInstanceError):
c.i = 5
self.assertNotHasAttr(c, 'i')
with self.assertRaises(FrozenInstanceError):
del c.i
@dataclass(frozen=True, slots=slots)
class C:
pass

c = C()
self.assertNotHasAttr(c, 'i')
with self.assertRaises(FrozenInstanceError):
c.i = 5
self.assertNotHasAttr(c, 'i')
with self.assertRaises(FrozenInstanceError):
del c.i

def test_inherit(self):
@dataclass(frozen=True)
Expand Down Expand Up @@ -3272,41 +3284,43 @@ class D(I):
d.i = 5

def test_non_frozen_normal_derived(self):
# See bpo-32953.
# See bpo-32953 and https://github.com/python/cpython/issues/105936
for slots in (False, True):
with self.subTest(slots=slots):

@dataclass(frozen=True)
class D:
x: int
y: int = 10
@dataclass(frozen=True, slots=slots)
class D:
x: int
y: int = 10

class S(D):
pass

s = S(3)
self.assertEqual(s.x, 3)
self.assertEqual(s.y, 10)
s.cached = True

# But can't change the frozen attributes.
with self.assertRaises(FrozenInstanceError):
s.x = 5
with self.assertRaises(FrozenInstanceError):
s.y = 5
self.assertEqual(s.x, 3)
self.assertEqual(s.y, 10)
self.assertEqual(s.cached, True)
class S(D):
pass

with self.assertRaises(FrozenInstanceError):
del s.x
self.assertEqual(s.x, 3)
with self.assertRaises(FrozenInstanceError):
del s.y
self.assertEqual(s.y, 10)
del s.cached
self.assertNotHasAttr(s, 'cached')
with self.assertRaises(AttributeError) as cm:
del s.cached
self.assertNotIsInstance(cm.exception, FrozenInstanceError)
s = S(3)
self.assertEqual(s.x, 3)
self.assertEqual(s.y, 10)
s.cached = True

# But can't change the frozen attributes.
with self.assertRaises(FrozenInstanceError):
s.x = 5
with self.assertRaises(FrozenInstanceError):
s.y = 5
self.assertEqual(s.x, 3)
self.assertEqual(s.y, 10)
self.assertEqual(s.cached, True)

with self.assertRaises(FrozenInstanceError):
del s.x
self.assertEqual(s.x, 3)
with self.assertRaises(FrozenInstanceError):
del s.y
self.assertEqual(s.y, 10)
del s.cached
self.assertNotHasAttr(s, 'cached')
with self.assertRaises(AttributeError) as cm:
del s.cached
self.assertNotIsInstance(cm.exception, FrozenInstanceError)

def test_non_frozen_normal_derived_from_empty_frozen(self):
@dataclass(frozen=True)
Expand Down Expand Up @@ -3974,6 +3988,14 @@ class SlotsTest:

return SlotsTest

# See https://github.com/python/cpython/issues/135228#issuecomment-3755979059
def make_frozen():
@dataclass(frozen=True, slots=True)
class SlotsTest:
pass

return SlotsTest

def make_with_annotations():
@dataclass(slots=True)
class SlotsTest:
Expand All @@ -3999,7 +4021,7 @@ class SlotsTest:

return SlotsTest

for make in (make_simple, make_with_annotations, make_with_annotations_and_method, make_with_forwardref):
for make in (make_simple, make_frozen, make_with_annotations, make_with_annotations_and_method, make_with_forwardref):
with self.subTest(make=make):
C = make()
support.gc_collect()
Expand Down Expand Up @@ -5343,5 +5365,51 @@ def cls(self):
# one will be keeping a reference to the underlying class A.
self.assertIs(A().cls(), B)

def test_empty_class_cell(self):
# gh-148947: Make sure that we explicitly handle the empty class cell.
def maker():
if False:
__class__ = 42

def method(self):
return __class__
return method

from dataclasses import dataclass

@dataclass(slots=True)
class X:
a: int

meth = maker()

with self.assertRaisesRegex(NameError, '__class__'):
X(1).meth()

def test_class_cell_from_other_class(self):
# This test fails without the "is oldcls" check in
# _update_func_cell_for__class__.
class Base:
def meth(self):
return "Base"

class Child(Base):
def meth(self):
return super().meth() + " Child"

@dataclass(slots=True)
class DC(Child):
a: int

meth = Child.meth

closure = DC.meth.__closure__
self.assertEqual(len(closure), 1)
self.assertIs(closure[0].cell_contents, Child)

self.assertEqual(DC(1).meth(), "Base Child")



if __name__ == '__main__':
unittest.main()
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