[Python-checkins] bpo-32960: For dataclasses, disallow inheriting frozen from non-frozen classes and vice-versa, (GH-5919) (GH-5920)
Eric V. Smith
webhook-mailer at python.org
Mon Feb 26 21:00:00 EST 2018
https://github.com/python/cpython/commit/a93e3dc236279692eaf50b91d358da5983983b14
commit: a93e3dc236279692eaf50b91d358da5983983b14
branch: 3.7
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: Eric V. Smith <ericvsmith at users.noreply.github.com>
date: 2018-02-26T20:59:55-05:00
summary:
bpo-32960: For dataclasses, disallow inheriting frozen from non-frozen classes and vice-versa, (GH-5919) (GH-5920)
This restriction will be relaxed at a future date.
(cherry picked from commit 2fa6b9eae07e2385e2acbf2e40093a21fb3a10c4)
Co-authored-by: Eric V. Smith <ericvsmith at users.noreply.github.com>
files:
A Misc/NEWS.d/next/Library/2018-02-26-20-04-40.bpo-32960.48r0Ml.rst
M Lib/dataclasses.py
M Lib/test/test_dataclasses.py
diff --git a/Lib/dataclasses.py b/Lib/dataclasses.py
index db92b10960d5..54478fec93df 100644
--- a/Lib/dataclasses.py
+++ b/Lib/dataclasses.py
@@ -623,14 +623,21 @@ def _process_class(cls, repr, eq, order, unsafe_hash, init, frozen):
else:
setattr(cls, f.name, f.default)
+ # We're inheriting from a frozen dataclass, but we're not frozen.
+ if cls.__setattr__ is _frozen_setattr and not frozen:
+ raise TypeError('cannot inherit non-frozen dataclass from a '
+ 'frozen one')
+
+ # We're inheriting from a non-frozen dataclass, but we're frozen.
+ if (hasattr(cls, _MARKER) and cls.__setattr__ is not _frozen_setattr
+ and frozen):
+ raise TypeError('cannot inherit frozen dataclass from a '
+ 'non-frozen one')
+
# Remember all of the fields on our class (including bases). This
# marks this class as being a dataclass.
setattr(cls, _MARKER, fields)
- # We also need to check if a parent class is frozen: frozen has to
- # be inherited down.
- is_frozen = frozen or cls.__setattr__ is _frozen_setattr
-
# 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
@@ -654,7 +661,7 @@ def _process_class(cls, repr, eq, order, unsafe_hash, init, frozen):
if f._field_type in (_FIELD, _FIELD_INITVAR)]
_set_new_attribute(cls, '__init__',
_init_fn(flds,
- is_frozen,
+ frozen,
has_post_init,
# The name to use for the "self" param
# in __init__. Use "self" if possible.
@@ -696,7 +703,7 @@ def _process_class(cls, repr, eq, order, unsafe_hash, init, frozen):
f'in class {cls.__name__}. Consider using '
'functools.total_ordering')
- if is_frozen:
+ if frozen:
for name, fn in [('__setattr__', _frozen_setattr),
('__delattr__', _frozen_delattr)]:
if _set_new_attribute(cls, name, fn):
diff --git a/Lib/test/test_dataclasses.py b/Lib/test/test_dataclasses.py
index 582cb3459f5d..46d485c0157b 100755
--- a/Lib/test/test_dataclasses.py
+++ b/Lib/test/test_dataclasses.py
@@ -637,29 +637,6 @@ class C:
y: int
self.assertNotEqual(Point(1, 3), C(1, 3))
- def test_frozen(self):
- @dataclass(frozen=True)
- class C:
- i: int
-
- c = C(10)
- self.assertEqual(c.i, 10)
- with self.assertRaises(FrozenInstanceError):
- c.i = 5
- self.assertEqual(c.i, 10)
-
- # Check that a derived class is still frozen, even if not
- # marked so.
- @dataclass
- class D(C):
- pass
-
- d = D(20)
- self.assertEqual(d.i, 20)
- with self.assertRaises(FrozenInstanceError):
- d.i = 5
- self.assertEqual(d.i, 20)
-
def test_not_tuple(self):
# Test that some of the problems with namedtuple don't happen
# here.
@@ -2475,5 +2452,66 @@ class C(base):
assert False, f'unknown value for expected={expected!r}'
+class TestFrozen(unittest.TestCase):
+ def test_frozen(self):
+ @dataclass(frozen=True)
+ class C:
+ i: int
+
+ c = C(10)
+ self.assertEqual(c.i, 10)
+ with self.assertRaises(FrozenInstanceError):
+ c.i = 5
+ self.assertEqual(c.i, 10)
+
+ def test_inherit(self):
+ @dataclass(frozen=True)
+ class C:
+ i: int
+
+ @dataclass(frozen=True)
+ class D(C):
+ j: int
+
+ d = D(0, 10)
+ with self.assertRaises(FrozenInstanceError):
+ d.i = 5
+ self.assertEqual(d.i, 0)
+
+ def test_inherit_from_nonfrozen_from_frozen(self):
+ @dataclass(frozen=True)
+ class C:
+ i: int
+
+ with self.assertRaisesRegex(TypeError,
+ 'cannot inherit non-frozen dataclass from a frozen one'):
+ @dataclass
+ class D(C):
+ pass
+
+ def test_inherit_from_frozen_from_nonfrozen(self):
+ @dataclass
+ class C:
+ i: int
+
+ with self.assertRaisesRegex(TypeError,
+ 'cannot inherit frozen dataclass from a non-frozen one'):
+ @dataclass(frozen=True)
+ class D(C):
+ pass
+
+ def test_inherit_from_normal_class(self):
+ class C:
+ pass
+
+ @dataclass(frozen=True)
+ class D(C):
+ i: int
+
+ d = D(10)
+ with self.assertRaises(FrozenInstanceError):
+ d.i = 5
+
+
if __name__ == '__main__':
unittest.main()
diff --git a/Misc/NEWS.d/next/Library/2018-02-26-20-04-40.bpo-32960.48r0Ml.rst b/Misc/NEWS.d/next/Library/2018-02-26-20-04-40.bpo-32960.48r0Ml.rst
new file mode 100644
index 000000000000..4ad1fa17571d
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2018-02-26-20-04-40.bpo-32960.48r0Ml.rst
@@ -0,0 +1,3 @@
+For dataclasses, disallow inheriting frozen from non-frozen classes, and
+also disallow inheriting non-frozen from frozen classes. This restriction
+will be relaxed at a future date.
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