cpython/Lib/test/test_dataclasses.py

from dataclasses import (
    dataclass, field, FrozenInstanceError, fields, asdict, astuple,
    make_dataclass, replace, InitVar, Field, MISSING, is_dataclass,
)

import pickle
import inspect
import unittest
from unittest.mock import Mock
from typing import ClassVar, Any, List, Union, Tuple, Dict, Generic, TypeVar
from collections import deque, OrderedDict, namedtuple

# Just any custom exception we can catch.
class CustomError(Exception): pass

class TestCase(unittest.TestCase):
    def test_no_fields(self):
        @dataclass
        class C:
            pass

        o = C()
        self.assertEqual(len(fields(C)), 0)

    def test_one_field_no_default(self):
        @dataclass
        class C:
            x: int

        o = C(42)
        self.assertEqual(o.x, 42)

    def test_named_init_params(self):
        @dataclass
        class C:
            x: int

        o = C(x=32)
        self.assertEqual(o.x, 32)

    def test_two_fields_one_default(self):
        @dataclass
        class C:
            x: int
            y: int = 0

        o = C(3)
        self.assertEqual((o.x, o.y), (3, 0))

        # Non-defaults following defaults.
        with self.assertRaisesRegex(TypeError,
                                    "non-default argument 'y' follows "
                                    "default argument"):
            @dataclass
            class C:
                x: int = 0
                y: int

        # A derived class adds a non-default field after a default one.
        with self.assertRaisesRegex(TypeError,
                                    "non-default argument 'y' follows "
                                    "default argument"):
            @dataclass
            class B:
                x: int = 0

            @dataclass
            class C(B):
                y: int

        # Override a base class field and add a default to
        #  a field which didn't use to have a default.
        with self.assertRaisesRegex(TypeError,
                                    "non-default argument 'y' follows "
                                    "default argument"):
            @dataclass
            class B:
                x: int
                y: int

            @dataclass
            class C(B):
                x: int = 0

    def test_overwriting_init(self):
        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __init__ '
                                    'in C'):
            @dataclass
            class C:
                x: int
                def __init__(self, x):
                    self.x = 2 * x

        @dataclass(init=False)
        class C:
            x: int
            def __init__(self, x):
                self.x = 2 * x
        self.assertEqual(C(5).x, 10)

    def test_overwriting_repr(self):
        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __repr__ '
                                    'in C'):
            @dataclass
            class C:
                x: int
                def __repr__(self):
                    pass

        @dataclass(repr=False)
        class C:
            x: int
            def __repr__(self):
                return 'x'
        self.assertEqual(repr(C(0)), 'x')

    def test_overwriting_cmp(self):
        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __eq__ '
                                    'in C'):
            # This will generate the comparison functions, make sure we can't
            #  overwrite them.
            @dataclass(hash=False, frozen=False)
            class C:
                x: int
                def __eq__(self):
                    pass

        @dataclass(order=False, eq=False)
        class C:
            x: int
            def __eq__(self, other):
                return True
        self.assertEqual(C(0), 'x')

    def test_overwriting_hash(self):
        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __hash__ '
                                    'in C'):
            @dataclass(frozen=True)
            class C:
                x: int
                def __hash__(self):
                    pass

        @dataclass(frozen=True,hash=False)
        class C:
            x: int
            def __hash__(self):
                return 600
        self.assertEqual(hash(C(0)), 600)

        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __hash__ '
                                    'in C'):
            @dataclass(frozen=True)
            class C:
                x: int
                def __hash__(self):
                    pass

        @dataclass(frozen=True, hash=False)
        class C:
            x: int
            def __hash__(self):
                return 600
        self.assertEqual(hash(C(0)), 600)

    def test_overwriting_frozen(self):
        # frozen uses __setattr__ and __delattr__
        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __setattr__ '
                                    'in C'):
            @dataclass(frozen=True)
            class C:
                x: int
                def __setattr__(self):
                    pass

        with self.assertRaisesRegex(TypeError,
                                    'Cannot overwrite attribute __delattr__ '
                                    'in C'):
            @dataclass(frozen=True)
            class C:
                x: int
                def __delattr__(self):
                    pass

        @dataclass(frozen=False)
        class C:
            x: int
            def __setattr__(self, name, value):
                self.__dict__['x'] = value * 2
        self.assertEqual(C(10).x, 20)

    def test_overwrite_fields_in_derived_class(self):
        # Note that x from C1 replaces x in Base, but the order remains
        #  the same as defined in Base.
        @dataclass
        class Base:
            x: Any = 15.0
            y: int = 0

        @dataclass
        class C1(Base):
            z: int = 10
            x: int = 15

        o = Base()
        self.assertEqual(repr(o), 'TestCase.test_overwrite_fields_in_derived_class.<locals>.Base(x=15.0, y=0)')

        o = C1()
        self.assertEqual(repr(o), 'TestCase.test_overwrite_fields_in_derived_class.<locals>.C1(x=15, y=0, z=10)')

        o = C1(x=5)
        self.assertEqual(repr(o), 'TestCase.test_overwrite_fields_in_derived_class.<locals>.C1(x=5, y=0, z=10)')

    def test_field_named_self(self):
        @dataclass
        class C:
            self: str
        c=C('foo')
        self.assertEqual(c.self, 'foo')

        # Make sure the first parameter is not named 'self'.
        sig = inspect.signature(C.__init__)
        first = next(iter(sig.parameters))
        self.assertNotEqual('self', first)

        # But we do use 'self' if no field named self.
        @dataclass
        class C:
            selfx: str

        # Make sure the first parameter is named 'self'.
        sig = inspect.signature(C.__init__)
        first = next(iter(sig.parameters))
        self.assertEqual('self', first)

    def test_repr(self):
        @dataclass
        class B:
            x: int

        @dataclass
        class C(B):
            y: int = 10

        o = C(4)
        self.assertEqual(repr(o), 'TestCase.test_repr.<locals>.C(x=4, y=10)')

        @dataclass
        class D(C):
            x: int = 20
        self.assertEqual(repr(D()), 'TestCase.test_repr.<locals>.D(x=20, y=10)')

        @dataclass
        class C:
            @dataclass
            class D:
                i: int
            @dataclass
            class E:
                pass
        self.assertEqual(repr(C.D(0)), 'TestCase.test_repr.<locals>.C.D(i=0)')
        self.assertEqual(repr(C.E()), 'TestCase.test_repr.<locals>.C.E()')

    def test_0_field_compare(self):
        # Ensure that order=False is the default.
        @dataclass
        class C0:
            pass

        @dataclass(order=False)
        class C1:
            pass

        for cls in [C0, C1]:
            with self.subTest(cls=cls):
                self.assertEqual(cls(), cls())
                for idx, fn in enumerate([lambda a, b: a < b,
                                          lambda a, b: a <= b,
                                          lambda a, b: a > b,
                                          lambda a, b: a >= b]):
                    with self.subTest(idx=idx):
                        with self.assertRaisesRegex(TypeError,
                                                    f"not supported between instances of '{cls.__name__}' and '{cls.__name__}'"):
                            fn(cls(), cls())

        @dataclass(order=True)
        class C:
            pass
        self.assertLessEqual(C(), C())
        self.assertGreaterEqual(C(), C())

    def test_1_field_compare(self):
        # Ensure that order=False is the default.
        @dataclass
        class C0:
            x: int

        @dataclass(order=False)
        class C1:
            x: int

        for cls in [C0, C1]:
            with self.subTest(cls=cls):
                self.assertEqual(cls(1), cls(1))
                self.assertNotEqual(cls(0), cls(1))
                for idx, fn in enumerate([lambda a, b: a < b,
                                          lambda a, b: a <= b,
                                          lambda a, b: a > b,
                                          lambda a, b: a >= b]):
                    with self.subTest(idx=idx):
                        with self.assertRaisesRegex(TypeError,
                                                    f"not supported between instances of '{cls.__name__}' and '{cls.__name__}'"):
                            fn(cls(0), cls(0))

        @dataclass(order=True)
        class C:
            x: int
        self.assertLess(C(0), C(1))
        self.assertLessEqual(C(0), C(1))
        self.assertLessEqual(C(1), C(1))
        self.assertGreater(C(1), C(0))
        self.assertGreaterEqual(C(1), C(0))
        self.assertGreaterEqual(C(1), C(1))

    def test_simple_compare(self):
        # Ensure that order=False is the default.
        @dataclass
        class C0:
            x: int
            y: int

        @dataclass(order=False)
        class C1:
            x: int
            y: int

        for cls in [C0, C1]:
            with self.subTest(cls=cls):
                self.assertEqual(cls(0, 0), cls(0, 0))
                self.assertEqual(cls(1, 2), cls(1, 2))
                self.assertNotEqual(cls(1, 0), cls(0, 0))
                self.assertNotEqual(cls(1, 0), cls(1, 1))
                for idx, fn in enumerate([lambda a, b: a < b,
                                          lambda a, b: a <= b,
                                          lambda a, b: a > b,
                                          lambda a, b: a >= b]):
                    with self.subTest(idx=idx):
                        with self.assertRaisesRegex(TypeError,
                                                    f"not supported between instances of '{cls.__name__}' and '{cls.__name__}'"):
                            fn(cls(0, 0), cls(0, 0))

        @dataclass(order=True)
        class C:
            x: int
            y: int

        for idx, fn in enumerate([lambda a, b: a == b,
                                  lambda a, b: a <= b,
                                  lambda a, b: a >= b]):
            with self.subTest(idx=idx):
                self.assertTrue(fn(C(0, 0), C(0, 0)))

        for idx, fn in enumerate([lambda a, b: a < b,
                                  lambda a, b: a <= b,
                                  lambda a, b: a != b]):
            with self.subTest(idx=idx):
                self.assertTrue(fn(C(0, 0), C(0, 1)))
                self.assertTrue(fn(C(0, 1), C(1, 0)))
                self.assertTrue(fn(C(1, 0), C(1, 1)))

        for idx, fn in enumerate([lambda a, b: a > b,
                                  lambda a, b: a >= b,
                                  lambda a, b: a != b]):
            with self.subTest(idx=idx):
                self.assertTrue(fn(C(0, 1), C(0, 0)))
                self.assertTrue(fn(C(1, 0), C(0, 1)))
                self.assertTrue(fn(C(1, 1), C(1, 0)))

    def test_compare_subclasses(self):
        # Comparisons fail for subclasses, even if no fields
        #  are added.
        @dataclass
        class B:
            i: int

        @dataclass
        class C(B):
            pass

        for idx, (fn, expected) in enumerate([(lambda a, b: a == b, False),
                                              (lambda a, b: a != b, True)]):
            with self.subTest(idx=idx):
                self.assertEqual(fn(B(0), C(0)), expected)

        for idx, fn in enumerate([lambda a, b: a < b,
                                  lambda a, b: a <= b,
                                  lambda a, b: a > b,
                                  lambda a, b: a >= b]):
            with self.subTest(idx=idx):
                with self.assertRaisesRegex(TypeError,
                                            "not supported between instances of 'B' and 'C'"):
                    fn(B(0), C(0))

    def test_0_field_hash(self):
        @dataclass(hash=True)
        class C:
            pass
        self.assertEqual(hash(C()), hash(()))

    def test_1_field_hash(self):
        @dataclass(hash=True)
        class C:
            x: int
        self.assertEqual(hash(C(4)), hash((4,)))
        self.assertEqual(hash(C(42)), hash((42,)))

    def test_hash(self):
        @dataclass(hash=True)
        class C:
            x: int
            y: str
        self.assertEqual(hash(C(1, 'foo')), hash((1, 'foo')))

    def test_no_hash(self):
        @dataclass(hash=None)
        class C:
            x: int
        with self.assertRaisesRegex(TypeError,
                                    "unhashable type: 'C'"):
            hash(C(1))

    def test_hash_rules(self):
        # There are 24 cases of:
        #  hash=True/False/None
        #  eq=True/False
        #  order=True/False
        #  frozen=True/False
        for (hash,  eq,    order, frozen, result  ) in [
            (False, False, False, False,  'absent'),
            (False, False, False, True,   'absent'),
            (False, False, True,  False,  'exception'),
            (False, False, True,  True,   'exception'),
            (False, True,  False, False,  'absent'),
            (False, True,  False, True,   'absent'),
            (False, True,  True,  False,  'absent'),
            (False, True,  True,  True,   'absent'),
            (True,  False, False, False,  'fn'),
            (True,  False, False, True,   'fn'),
            (True,  False, True,  False,  'exception'),
            (True,  False, True,  True,   'exception'),
            (True,  True,  False, False,  'fn'),
            (True,  True,  False, True,   'fn'),
            (True,  True,  True,  False,  'fn'),
            (True,  True,  True,  True,   'fn'),
            (None,  False, False, False,  'absent'),
            (None,  False, False, True,   'absent'),
            (None,  False, True,  False,  'exception'),
            (None,  False, True,  True,   'exception'),
            (None,  True,  False, False,  'none'),
            (None,  True,  False, True,   'fn'),
            (None,  True,  True,  False,  'none'),
            (None,  True,  True,  True,   'fn'),
        ]:
            with self.subTest(hash=hash, eq=eq, order=order, frozen=frozen):
                if result == 'exception':
                    with self.assertRaisesRegex(ValueError, 'eq must be true if order is true'):
                        @dataclass(hash=hash, eq=eq, order=order, frozen=frozen)
                        class C:
                            pass
                else:
                    @dataclass(hash=hash, eq=eq, order=order, frozen=frozen)
                    class C:
                        pass

                    # See if the result matches what's expected.
                    if result == 'fn':
                        # __hash__ contains the function we generated.
                        self.assertIn('__hash__', C.__dict__)
                        self.assertIsNotNone(C.__dict__['__hash__'])
                    elif result == 'absent':
                        # __hash__ is not present in our class.
                        self.assertNotIn('__hash__', C.__dict__)
                    elif result == 'none':
                        # __hash__ is set to None.
                        self.assertIn('__hash__', C.__dict__)
                        self.assertIsNone(C.__dict__['__hash__'])
                    else:
                        assert False, f'unknown result {result!r}'

    def test_eq_order(self):
        for (eq,    order, result   ) in [
            (False, False, 'neither'),
            (False, True,  'exception'),
            (True,  False, 'eq_only'),
            (True,  True,  'both'),
        ]:
            with self.subTest(eq=eq, order=order):
                if result == 'exception':
                    with self.assertRaisesRegex(ValueError, 'eq must be true if order is true'):
                        @dataclass(eq=eq, order=order)
                        class C:
                            pass
                else:
                    @dataclass(eq=eq, order=order)
                    class C:
                        pass

                    if result == 'neither':
                        self.assertNotIn('__eq__', C.__dict__)
                        self.assertNotIn('__ne__', C.__dict__)
                        self.assertNotIn('__lt__', C.__dict__)
                        self.assertNotIn('__le__', C.__dict__)
                        self.assertNotIn('__gt__', C.__dict__)
                        self.assertNotIn('__ge__', C.__dict__)
                    elif result == 'both':
                        self.assertIn('__eq__', C.__dict__)
                        self.assertIn('__ne__', C.__dict__)
                        self.assertIn('__lt__', C.__dict__)
                        self.assertIn('__le__', C.__dict__)
                        self.assertIn('__gt__', C.__dict__)
                        self.assertIn('__ge__', C.__dict__)
                    elif result == 'eq_only':
                        self.assertIn('__eq__', C.__dict__)
                        self.assertIn('__ne__', C.__dict__)
                        self.assertNotIn('__lt__', C.__dict__)
                        self.assertNotIn('__le__', C.__dict__)
                        self.assertNotIn('__gt__', C.__dict__)
                        self.assertNotIn('__ge__', C.__dict__)
                    else:
                        assert False, f'unknown result {result!r}'

    def test_field_no_default(self):
        @dataclass
        class C:
            x: int = field()

        self.assertEqual(C(5).x, 5)

        with self.assertRaisesRegex(TypeError,
                                    r"__init__\(\) missing 1 required "
                                    "positional argument: 'x'"):
            C()

    def test_field_default(self):
        default = object()
        @dataclass
        class C:
            x: object = field(default=default)

        self.assertIs(C.x, default)
        c = C(10)
        self.assertEqual(c.x, 10)

        # If we delete the instance attribute, we should then see the
        #  class attribute.
        del c.x
        self.assertIs(c.x, default)

        self.assertIs(C().x, default)

    def test_not_in_repr(self):
        @dataclass
        class C:
            x: int = field(repr=False)
        with self.assertRaises(TypeError):
            C()
        c = C(10)
        self.assertEqual(repr(c), 'TestCase.test_not_in_repr.<locals>.C()')

        @dataclass
        class C:
            x: int = field(repr=False)
            y: int
        c = C(10, 20)
        self.assertEqual(repr(c), 'TestCase.test_not_in_repr.<locals>.C(y=20)')

    def test_not_in_compare(self):
        @dataclass
        class C:
            x: int = 0
            y: int = field(compare=False, default=4)

        self.assertEqual(C(), C(0, 20))
        self.assertEqual(C(1, 10), C(1, 20))
        self.assertNotEqual(C(3), C(4, 10))
        self.assertNotEqual(C(3, 10), C(4, 10))

    def test_hash_field_rules(self):
        # Test all 6 cases of:
        #  hash=True/False/None
        #  compare=True/False
        for (hash_val, compare, result  ) in [
            (True,     False,   'field' ),
            (True,     True,    'field' ),
            (False,    False,   'absent'),
            (False,    True,    'absent'),
            (None,     False,   'absent'),
            (None,     True,    'field' ),
        ]:
            with self.subTest(hash_val=hash_val, compare=compare):
                @dataclass(hash=True)
                class C:
                    x: int = field(compare=compare, hash=hash_val, default=5)

                if result == 'field':
                    # __hash__ contains the field.
                    self.assertEqual(C(5).__hash__(), hash((5,)))
                elif result == 'absent':
                    # The field is not present in the hash.
                    self.assertEqual(C(5).__hash__(), hash(()))
                else:
                    assert False, f'unknown result {result!r}'

    def test_init_false_no_default(self):
        # If init=False and no default value, then the field won't be
        #  present in the instance.
        @dataclass
        class C:
            x: int = field(init=False)

        self.assertNotIn('x', C().__dict__)

        @dataclass
        class C:
            x: int
            y: int = 0
            z: int = field(init=False)
            t: int = 10

        self.assertNotIn('z', C(0).__dict__)
        self.assertEqual(vars(C(5)), {'t': 10, 'x': 5, 'y': 0})

    def test_class_marker(self):
        @dataclass
        class C:
            x: int
            y: str = field(init=False, default=None)
            z: str = field(repr=False)

        the_fields = fields(C)
        # the_fields is a tuple of 3 items, each value
        #  is in __annotations__.
        self.assertIsInstance(the_fields, tuple)
        for f in the_fields:
            self.assertIs(type(f), Field)
            self.assertIn(f.name, C.__annotations__)

        self.assertEqual(len(the_fields), 3)

        self.assertEqual(the_fields[0].name, 'x')
        self.assertEqual(the_fields[0].type, int)
        self.assertFalse(hasattr(C, 'x'))
        self.assertTrue (the_fields[0].init)
        self.assertTrue (the_fields[0].repr)
        self.assertEqual(the_fields[1].name, 'y')
        self.assertEqual(the_fields[1].type, str)
        self.assertIsNone(getattr(C, 'y'))
        self.assertFalse(the_fields[1].init)
        self.assertTrue (the_fields[1].repr)
        self.assertEqual(the_fields[2].name, 'z')
        self.assertEqual(the_fields[2].type, str)
        self.assertFalse(hasattr(C, 'z'))
        self.assertTrue (the_fields[2].init)
        self.assertFalse(the_fields[2].repr)

    def test_field_order(self):
        @dataclass
        class B:
            a: str = 'B:a'
            b: str = 'B:b'
            c: str = 'B:c'

        @dataclass
        class C(B):
            b: str = 'C:b'

        self.assertEqual([(f.name, f.default) for f in fields(C)],
                         [('a', 'B:a'),
                          ('b', 'C:b'),
                          ('c', 'B:c')])

        @dataclass
        class D(B):
            c: str = 'D:c'

        self.assertEqual([(f.name, f.default) for f in fields(D)],
                         [('a', 'B:a'),
                          ('b', 'B:b'),
                          ('c', 'D:c')])

        @dataclass
        class E(D):
            a: str = 'E:a'
            d: str = 'E:d'

        self.assertEqual([(f.name, f.default) for f in fields(E)],
                         [('a', 'E:a'),
                          ('b', 'B:b'),
                          ('c', 'D:c'),
                          ('d', 'E:d')])

    def test_class_attrs(self):
        # We only have a class attribute if a default value is
        #  specified, either directly or via a field with a default.
        default = object()
        @dataclass
        class C:
            x: int
            y: int = field(repr=False)
            z: object = default
            t: int = field(default=100)

        self.assertFalse(hasattr(C, 'x'))
        self.assertFalse(hasattr(C, 'y'))
        self.assertIs   (C.z, default)
        self.assertEqual(C.t, 100)

    def test_disallowed_mutable_defaults(self):
        # For the known types, don't allow mutable default values.
        for typ, empty, non_empty in [(list, [], [1]),
                                      (dict, {}, {0:1}),
                                      (set, set(), set([1])),
                                      ]:
            with self.subTest(typ=typ):
                # Can't use a zero-length value.
                with self.assertRaisesRegex(ValueError,
                                            f'mutable default {typ} for field '
                                            'x is not allowed'):
                    @dataclass
                    class Point:
                        x: typ = empty


                # Nor a non-zero-length value
                with self.assertRaisesRegex(ValueError,
                                            f'mutable default {typ} for field '
                                            'y is not allowed'):
                    @dataclass
                    class Point:
                        y: typ = non_empty

                # Check subtypes also fail.
                class Subclass(typ): pass

                with self.assertRaisesRegex(ValueError,
                                            f"mutable default .*Subclass'>"
                                            ' for field z is not allowed'
                                            ):
                    @dataclass
                    class Point:
                        z: typ = Subclass()

                # Because this is a ClassVar, it can be mutable.
                @dataclass
                class C:
                    z: ClassVar[typ] = typ()

                # Because this is a ClassVar, it can be mutable.
                @dataclass
                class C:
                    x: ClassVar[typ] = Subclass()


    def test_deliberately_mutable_defaults(self):
        # If a mutable default isn't in the known list of
        #  (list, dict, set), then it's okay.
        class Mutable:
            def __init__(self):
                self.l = []

        @dataclass
        class C:
            x: Mutable

        # These 2 instances will share this value of x.
        lst = Mutable()
        o1 = C(lst)
        o2 = C(lst)
        self.assertEqual(o1, o2)
        o1.x.l.extend([1, 2])
        self.assertEqual(o1, o2)
        self.assertEqual(o1.x.l, [1, 2])
        self.assertIs(o1.x, o2.x)

    def test_no_options(self):
        # call with dataclass()
        @dataclass()
        class C:
            x: int

        self.assertEqual(C(42).x, 42)

    def test_not_tuple(self):
        # Make sure we can't be compared to a tuple.
        @dataclass
        class Point:
            x: int
            y: int
        self.assertNotEqual(Point(1, 2), (1, 2))

        # And that we can't compare to another unrelated dataclass
        @dataclass
        class C:
            x: int
            y: int
        self.assertNotEqual(Point(1, 3), C(1, 3))

    def test_base_has_init(self):
        class B:
            def __init__(self):
                pass

        # Make sure that declaring this class doesn't raise an error.
        #  The issue is that we can't override __init__ in our class,
        #  but it should be okay to add __init__ to us if our base has
        #  an __init__.
        @dataclass
        class C(B):
            x: int = 0

    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.
        @dataclass
        class Point3D:
            x: int
            y: int
            z: int

        @dataclass
        class Date:
            year: int
            month: int
            day: int

        self.assertNotEqual(Point3D(2017, 6, 3), Date(2017, 6, 3))
        self.assertNotEqual(Point3D(1, 2, 3), (1, 2, 3))

        # Make sure we can't unpack
        with self.assertRaisesRegex(TypeError, 'unpack'):
            x, y, z = Point3D(4, 5, 6)

        # Maka sure another class with the same field names isn't
        #  equal.
        @dataclass
        class Point3Dv1:
            x: int = 0
            y: int = 0
            z: int = 0
        self.assertNotEqual(Point3D(0, 0, 0), Point3Dv1())

    def test_function_annotations(self):
        # Some dummy class and instance to use as a default.
        class F:
            pass
        f = F()

        def validate_class(cls):
            # First, check __annotations__, even though they're not
            #  function annotations.
            self.assertEqual(cls.__annotations__['i'], int)
            self.assertEqual(cls.__annotations__['j'], str)
            self.assertEqual(cls.__annotations__['k'], F)
            self.assertEqual(cls.__annotations__['l'], float)
            self.assertEqual(cls.__annotations__['z'], complex)

            # Verify __init__.

            signature = inspect.signature(cls.__init__)
            # Check the return type, should be None
            self.assertIs(signature.return_annotation, None)

            # Check each parameter.
            params = iter(signature.parameters.values())
            param = next(params)
            # This is testing an internal name, and probably shouldn't be tested.
            self.assertEqual(param.name, 'self')
            param = next(params)
            self.assertEqual(param.name, 'i')
            self.assertIs   (param.annotation, int)
            self.assertEqual(param.default, inspect.Parameter.empty)
            self.assertEqual(param.kind, inspect.Parameter.POSITIONAL_OR_KEYWORD)
            param = next(params)
            self.assertEqual(param.name, 'j')
            self.assertIs   (param.annotation, str)
            self.assertEqual(param.default, inspect.Parameter.empty)
            self.assertEqual(param.kind, inspect.Parameter.POSITIONAL_OR_KEYWORD)
            param = next(params)
            self.assertEqual(param.name, 'k')
            self.assertIs   (param.annotation, F)
            # Don't test for the default, since it's set to MISSING
            self.assertEqual(param.kind, inspect.Parameter.POSITIONAL_OR_KEYWORD)
            param = next(params)
            self.assertEqual(param.name, 'l')
            self.assertIs   (param.annotation, float)
            # Don't test for the default, since it's set to MISSING
            self.assertEqual(param.kind, inspect.Parameter.POSITIONAL_OR_KEYWORD)
            self.assertRaises(StopIteration, next, params)


        @dataclass
        class C:
            i: int
            j: str
            k: F = f
            l: float=field(default=None)
            z: complex=field(default=3+4j, init=False)

        validate_class(C)

        # Now repeat with __hash__.
        @dataclass(frozen=True, hash=True)
        class C:
            i: int
            j: str
            k: F = f
            l: float=field(default=None)
            z: complex=field(default=3+4j, init=False)

        validate_class(C)

    def test_missing_default(self):
        # Test that MISSING works the same as a default not being
        #  specified.
        @dataclass
        class C:
            x: int=field(default=MISSING)
        with self.assertRaisesRegex(TypeError,
                                    r'__init__\(\) missing 1 required '
                                    'positional argument'):
            C()
        self.assertNotIn('x', C.__dict__)

        @dataclass
        class D:
            x: int
        with self.assertRaisesRegex(TypeError,
                                    r'__init__\(\) missing 1 required '
                                    'positional argument'):
            D()
        self.assertNotIn('x', D.__dict__)

    def test_missing_default_factory(self):
        # Test that MISSING works the same as a default factory not
        #  being specified (which is really the same as a default not
        #  being specified, too).
        @dataclass
        class C:
            x: int=field(default_factory=MISSING)
        with self.assertRaisesRegex(TypeError,
                                    r'__init__\(\) missing 1 required '
                                    'positional argument'):
            C()
        self.assertNotIn('x', C.__dict__)

        @dataclass
        class D:
            x: int=field(default=MISSING, default_factory=MISSING)
        with self.assertRaisesRegex(TypeError,
                                    r'__init__\(\) missing 1 required '
                                    'positional argument'):
            D()
        self.assertNotIn('x', D.__dict__)

    def test_missing_repr(self):
        self.assertIn('MISSING_TYPE object', repr(MISSING))

    def test_dont_include_other_annotations(self):
        @dataclass
        class C:
            i: int
            def foo(self) -> int:
                return 4
            @property
            def bar(self) -> int:
                return 5
        self.assertEqual(list(C.__annotations__), ['i'])
        self.assertEqual(C(10).foo(), 4)
        self.assertEqual(C(10).bar, 5)

    def test_post_init(self):
        # Just make sure it gets called
        @dataclass
        class C:
            def __post_init__(self):
                raise CustomError()
        with self.assertRaises(CustomError):
            C()

        @dataclass
        class C:
            i: int = 10
            def __post_init__(self):
                if self.i == 10:
                    raise CustomError()
        with self.assertRaises(CustomError):
            C()
        # post-init gets called, but doesn't raise. This is just
        #  checking that self is used correctly.
        C(5)

        # If there's not an __init__, then post-init won't get called.
        @dataclass(init=False)
        class C:
            def __post_init__(self):
                raise CustomError()
        # Creating the class won't raise
        C()

        @dataclass
        class C:
            x: int = 0
            def __post_init__(self):
                self.x *= 2
        self.assertEqual(C().x, 0)
        self.assertEqual(C(2).x, 4)

        # Make sure that if we're frozen, post-init can't set
        #  attributes.
        @dataclass(frozen=True)
        class C:
            x: int = 0
            def __post_init__(self):
                self.x *= 2
        with self.assertRaises(FrozenInstanceError):
            C()

    def test_post_init_super(self):
        # Make sure super() post-init isn't called by default.
        class B:
            def __post_init__(self):
                raise CustomError()

        @dataclass
        class C(B):
            def __post_init__(self):
                self.x = 5

        self.assertEqual(C().x, 5)

        # Now call super(), and it will raise
        @dataclass
        class C(B):
            def __post_init__(self):
                super().__post_init__()

        with self.assertRaises(CustomError):
            C()

        # Make sure post-init is called, even if not defined in our
        #  class.
        @dataclass
        class C(B):
            pass

        with self.assertRaises(CustomError):
            C()

    def test_post_init_staticmethod(self):
        flag = False
        @dataclass
        class C:
            x: int
            y: int
            @staticmethod
            def __post_init__():
                nonlocal flag
                flag = True

        self.assertFalse(flag)
        c = C(3, 4)
        self.assertEqual((c.x, c.y), (3, 4))
        self.assertTrue(flag)

    def test_post_init_classmethod(self):
        @dataclass
        class C:
            flag = False
            x: int
            y: int
            @classmethod
            def __post_init__(cls):
                cls.flag = True

        self.assertFalse(C.flag)
        c = C(3, 4)
        self.assertEqual((c.x, c.y), (3, 4))
        self.assertTrue(C.flag)

    def test_class_var(self):
        # Make sure ClassVars are ignored in __init__, __repr__, etc.
        @dataclass
        class C:
            x: int
            y: int = 10
            z: ClassVar[int] = 1000
            w: ClassVar[int] = 2000
            t: ClassVar[int] = 3000

        c = C(5)
        self.assertEqual(repr(c), 'TestCase.test_class_var.<locals>.C(x=5, y=10)')
        self.assertEqual(len(fields(C)), 2)                 # We have 2 fields
        self.assertEqual(len(C.__annotations__), 5)         # And 3 ClassVars
        self.assertEqual(c.z, 1000)
        self.assertEqual(c.w, 2000)
        self.assertEqual(c.t, 3000)
        C.z += 1
        self.assertEqual(c.z, 1001)
        c = C(20)
        self.assertEqual((c.x, c.y), (20, 10))
        self.assertEqual(c.z, 1001)
        self.assertEqual(c.w, 2000)
        self.assertEqual(c.t, 3000)

    def test_class_var_no_default(self):
        # If a ClassVar has no default value, it should not be set on the class.
        @dataclass
        class C:
            x: ClassVar[int]

        self.assertNotIn('x', C.__dict__)

    def test_class_var_default_factory(self):
        # It makes no sense for a ClassVar to have a default factory. When
        #  would it be called? Call it yourself, since it's class-wide.
        with self.assertRaisesRegex(TypeError,
                                    'cannot have a default factory'):
            @dataclass
            class C:
                x: ClassVar[int] = field(default_factory=int)

            self.assertNotIn('x', C.__dict__)

    def test_class_var_with_default(self):
        # If a ClassVar has a default value, it should be set on the class.
        @dataclass
        class C:
            x: ClassVar[int] = 10
        self.assertEqual(C.x, 10)

        @dataclass
        class C:
            x: ClassVar[int] = field(default=10)
        self.assertEqual(C.x, 10)

    def test_class_var_frozen(self):
        # Make sure ClassVars work even if we're frozen.
        @dataclass(frozen=True)
        class C:
            x: int
            y: int = 10
            z: ClassVar[int] = 1000
            w: ClassVar[int] = 2000
            t: ClassVar[int] = 3000

        c = C(5)
        self.assertEqual(repr(C(5)), 'TestCase.test_class_var_frozen.<locals>.C(x=5, y=10)')
        self.assertEqual(len(fields(C)), 2)                 # We have 2 fields
        self.assertEqual(len(C.__annotations__), 5)         # And 3 ClassVars
        self.assertEqual(c.z, 1000)
        self.assertEqual(c.w, 2000)
        self.assertEqual(c.t, 3000)
        # We can still modify the ClassVar, it's only instances that are
        #  frozen.
        C.z += 1
        self.assertEqual(c.z, 1001)
        c = C(20)
        self.assertEqual((c.x, c.y), (20, 10))
        self.assertEqual(c.z, 1001)
        self.assertEqual(c.w, 2000)
        self.assertEqual(c.t, 3000)

    def test_init_var_no_default(self):
        # If an InitVar has no default value, it should not be set on the class.
        @dataclass
        class C:
            x: InitVar[int]

        self.assertNotIn('x', C.__dict__)

    def test_init_var_default_factory(self):
        # It makes no sense for an InitVar to have a default factory. When
        #  would it be called? Call it yourself, since it's class-wide.
        with self.assertRaisesRegex(TypeError,
                                    'cannot have a default factory'):
            @dataclass
            class C:
                x: InitVar[int] = field(default_factory=int)

            self.assertNotIn('x', C.__dict__)

    def test_init_var_with_default(self):
        # If an InitVar has a default value, it should be set on the class.
        @dataclass
        class C:
            x: InitVar[int] = 10
        self.assertEqual(C.x, 10)

        @dataclass
        class C:
            x: InitVar[int] = field(default=10)
        self.assertEqual(C.x, 10)

    def test_init_var(self):
        @dataclass
        class C:
            x: int = None
            init_param: InitVar[int] = None

            def __post_init__(self, init_param):
                if self.x is None:
                    self.x = init_param*2

        c = C(init_param=10)
        self.assertEqual(c.x, 20)

    def test_init_var_inheritance(self):
        # Note that this deliberately tests that a dataclass need not
        #  have a __post_init__ function if it has an InitVar field.
        #  It could just be used in a derived class, as shown here.
        @dataclass
        class Base:
            x: int
            init_base: InitVar[int]

        # We can instantiate by passing the InitVar, even though
        #  it's not used.
        b = Base(0, 10)
        self.assertEqual(vars(b), {'x': 0})

        @dataclass
        class C(Base):
            y: int
            init_derived: InitVar[int]

            def __post_init__(self, init_base, init_derived):
                self.x = self.x + init_base
                self.y = self.y + init_derived

        c = C(10, 11, 50, 51)
        self.assertEqual(vars(c), {'x': 21, 'y': 101})

    def test_default_factory(self):
        # Test a factory that returns a new list.
        @dataclass
        class C:
            x: int
            y: list = field(default_factory=list)

        c0 = C(3)
        c1 = C(3)
        self.assertEqual(c0.x, 3)
        self.assertEqual(c0.y, [])
        self.assertEqual(c0, c1)
        self.assertIsNot(c0.y, c1.y)
        self.assertEqual(astuple(C(5, [1])), (5, [1]))

        # Test a factory that returns a shared list.
        l = []
        @dataclass
        class C:
            x: int
            y: list = field(default_factory=lambda: l)

        c0 = C(3)
        c1 = C(3)
        self.assertEqual(c0.x, 3)
        self.assertEqual(c0.y, [])
        self.assertEqual(c0, c1)
        self.assertIs(c0.y, c1.y)
        self.assertEqual(astuple(C(5, [1])), (5, [1]))

        # Test various other field flags.
        # repr
        @dataclass
        class C:
            x: list = field(default_factory=list, repr=False)
        self.assertEqual(repr(C()), 'TestCase.test_default_factory.<locals>.C()')
        self.assertEqual(C().x, [])

        # hash
        @dataclass(hash=True)
        class C:
            x: list = field(default_factory=list, hash=False)
        self.assertEqual(astuple(C()), ([],))
        self.assertEqual(hash(C()), hash(()))

        # init (see also test_default_factory_with_no_init)
        @dataclass
        class C:
            x: list = field(default_factory=list, init=False)
        self.assertEqual(astuple(C()), ([],))

        # compare
        @dataclass
        class C:
            x: list = field(default_factory=list, compare=False)
        self.assertEqual(C(), C([1]))

    def test_default_factory_with_no_init(self):
        # We need a factory with a side effect.
        factory = Mock()

        @dataclass
        class C:
            x: list = field(default_factory=factory, init=False)

        # Make sure the default factory is called for each new instance.
        C().x
        self.assertEqual(factory.call_count, 1)
        C().x
        self.assertEqual(factory.call_count, 2)

    def test_default_factory_not_called_if_value_given(self):
        # We need a factory that we can test if it's been called.
        factory = Mock()

        @dataclass
        class C:
            x: int = field(default_factory=factory)

        # Make sure that if a field has a default factory function,
        #  it's not called if a value is specified.
        C().x
        self.assertEqual(factory.call_count, 1)
        self.assertEqual(C(10).x, 10)
        self.assertEqual(factory.call_count, 1)
        C().x
        self.assertEqual(factory.call_count, 2)

    def x_test_classvar_default_factory(self):
        # XXX: it's an error for a ClassVar to have a factory function
        @dataclass
        class C:
            x: ClassVar[int] = field(default_factory=int)

        self.assertIs(C().x, int)

    def test_is_dataclass(self):
        class NotDataClass:
            pass

        self.assertFalse(is_dataclass(0))
        self.assertFalse(is_dataclass(int))
        self.assertFalse(is_dataclass(NotDataClass))
        self.assertFalse(is_dataclass(NotDataClass()))

        @dataclass
        class C:
            x: int

        @dataclass
        class D:
            d: C
            e: int

        c = C(10)
        d = D(c, 4)

        self.assertTrue(is_dataclass(C))
        self.assertTrue(is_dataclass(c))
        self.assertFalse(is_dataclass(c.x))
        self.assertTrue(is_dataclass(d.d))
        self.assertFalse(is_dataclass(d.e))

    def test_helper_fields_with_class_instance(self):
        # Check that we can call fields() on either a class or instance,
        #  and get back the same thing.
        @dataclass
        class C:
            x: int
            y: float

        self.assertEqual(fields(C), fields(C(0, 0.0)))

    def test_helper_fields_exception(self):
        # Check that TypeError is raised if not passed a dataclass or
        #  instance.
        with self.assertRaisesRegex(TypeError, 'dataclass type or instance'):
            fields(0)

        class C: pass
        with self.assertRaisesRegex(TypeError, 'dataclass type or instance'):
            fields(C)
        with self.assertRaisesRegex(TypeError, 'dataclass type or instance'):
            fields(C())

    def test_helper_asdict(self):
        # Basic tests for asdict(), it should return a new dictionary
        @dataclass
        class C:
            x: int
            y: int
        c = C(1, 2)

        self.assertEqual(asdict(c), {'x': 1, 'y': 2})
        self.assertEqual(asdict(c), asdict(c))
        self.assertIsNot(asdict(c), asdict(c))
        c.x = 42
        self.assertEqual(asdict(c), {'x': 42, 'y': 2})
        self.assertIs(type(asdict(c)), dict)

    def test_helper_asdict_raises_on_classes(self):
        # asdict() should raise on a class object
        @dataclass
        class C:
            x: int
            y: int
        with self.assertRaisesRegex(TypeError, 'dataclass instance'):
            asdict(C)
        with self.assertRaisesRegex(TypeError, 'dataclass instance'):
            asdict(int)

    def test_helper_asdict_copy_values(self):
        @dataclass
        class C:
            x: int
            y: List[int] = field(default_factory=list)
        initial = []
        c = C(1, initial)
        d = asdict(c)
        self.assertEqual(d['y'], initial)
        self.assertIsNot(d['y'], initial)
        c = C(1)
        d = asdict(c)
        d['y'].append(1)
        self.assertEqual(c.y, [])

    def test_helper_asdict_nested(self):
        @dataclass
        class UserId:
            token: int
            group: int
        @dataclass
        class User:
            name: str
            id: UserId
        u = User('Joe', UserId(123, 1))
        d = asdict(u)
        self.assertEqual(d, {'name': 'Joe', 'id': {'token': 123, 'group': 1}})
        self.assertIsNot(asdict(u), asdict(u))
        u.id.group = 2
        self.assertEqual(asdict(u), {'name': 'Joe',
                                     'id': {'token': 123, 'group': 2}})

    def test_helper_asdict_builtin_containers(self):
        @dataclass
        class User:
            name: str
            id: int
        @dataclass
        class GroupList:
            id: int
            users: List[User]
        @dataclass
        class GroupTuple:
            id: int
            users: Tuple[User, ...]
        @dataclass
        class GroupDict:
            id: int
            users: Dict[str, User]
        a = User('Alice', 1)
        b = User('Bob', 2)
        gl = GroupList(0, [a, b])
        gt = GroupTuple(0, (a, b))
        gd = GroupDict(0, {'first': a, 'second': b})
        self.assertEqual(asdict(gl), {'id': 0, 'users': [{'name': 'Alice', 'id': 1},
                                                         {'name': 'Bob', 'id': 2}]})
        self.assertEqual(asdict(gt), {'id': 0, 'users': ({'name': 'Alice', 'id': 1},
                                                         {'name': 'Bob', 'id': 2})})
        self.assertEqual(asdict(gd), {'id': 0, 'users': {'first': {'name': 'Alice', 'id': 1},
                                                         'second': {'name': 'Bob', 'id': 2}}})

    def test_helper_asdict_builtin_containers(self):
        @dataclass
        class Child:
            d: object

        @dataclass
        class Parent:
            child: Child

        self.assertEqual(asdict(Parent(Child([1]))), {'child': {'d': [1]}})
        self.assertEqual(asdict(Parent(Child({1: 2}))), {'child': {'d': {1: 2}}})

    def test_helper_asdict_factory(self):
        @dataclass
        class C:
            x: int
            y: int
        c = C(1, 2)
        d = asdict(c, dict_factory=OrderedDict)
        self.assertEqual(d, OrderedDict([('x', 1), ('y', 2)]))
        self.assertIsNot(d, asdict(c, dict_factory=OrderedDict))
        c.x = 42
        d = asdict(c, dict_factory=OrderedDict)
        self.assertEqual(d, OrderedDict([('x', 42), ('y', 2)]))
        self.assertIs(type(d), OrderedDict)

    def test_helper_astuple(self):
        # Basic tests for astuple(), it should return a new tuple
        @dataclass
        class C:
            x: int
            y: int = 0
        c = C(1)

        self.assertEqual(astuple(c), (1, 0))
        self.assertEqual(astuple(c), astuple(c))
        self.assertIsNot(astuple(c), astuple(c))
        c.y = 42
        self.assertEqual(astuple(c), (1, 42))
        self.assertIs(type(astuple(c)), tuple)

    def test_helper_astuple_raises_on_classes(self):
        # astuple() should raise on a class object
        @dataclass
        class C:
            x: int
            y: int
        with self.assertRaisesRegex(TypeError, 'dataclass instance'):
            astuple(C)
        with self.assertRaisesRegex(TypeError, 'dataclass instance'):
            astuple(int)

    def test_helper_astuple_copy_values(self):
        @dataclass
        class C:
            x: int
            y: List[int] = field(default_factory=list)
        initial = []
        c = C(1, initial)
        t = astuple(c)
        self.assertEqual(t[1], initial)
        self.assertIsNot(t[1], initial)
        c = C(1)
        t = astuple(c)
        t[1].append(1)
        self.assertEqual(c.y, [])

    def test_helper_astuple_nested(self):
        @dataclass
        class UserId:
            token: int
            group: int
        @dataclass
        class User:
            name: str
            id: UserId
        u = User('Joe', UserId(123, 1))
        t = astuple(u)
        self.assertEqual(t, ('Joe', (123, 1)))
        self.assertIsNot(astuple(u), astuple(u))
        u.id.group = 2
        self.assertEqual(astuple(u), ('Joe', (123, 2)))

    def test_helper_astuple_builtin_containers(self):
        @dataclass
        class User:
            name: str
            id: int
        @dataclass
        class GroupList:
            id: int
            users: List[User]
        @dataclass
        class GroupTuple:
            id: int
            users: Tuple[User, ...]
        @dataclass
        class GroupDict:
            id: int
            users: Dict[str, User]
        a = User('Alice', 1)
        b = User('Bob', 2)
        gl = GroupList(0, [a, b])
        gt = GroupTuple(0, (a, b))
        gd = GroupDict(0, {'first': a, 'second': b})
        self.assertEqual(astuple(gl), (0, [('Alice', 1), ('Bob', 2)]))
        self.assertEqual(astuple(gt), (0, (('Alice', 1), ('Bob', 2))))
        self.assertEqual(astuple(gd), (0, {'first': ('Alice', 1), 'second': ('Bob', 2)}))

    def test_helper_astuple_builtin_containers(self):
        @dataclass
        class Child:
            d: object

        @dataclass
        class Parent:
            child: Child

        self.assertEqual(astuple(Parent(Child([1]))), (([1],),))
        self.assertEqual(astuple(Parent(Child({1: 2}))), (({1: 2},),))

    def test_helper_astuple_factory(self):
        @dataclass
        class C:
            x: int
            y: int
        NT = namedtuple('NT', 'x y')
        def nt(lst):
            return NT(*lst)
        c = C(1, 2)
        t = astuple(c, tuple_factory=nt)
        self.assertEqual(t, NT(1, 2))
        self.assertIsNot(t, astuple(c, tuple_factory=nt))
        c.x = 42
        t = astuple(c, tuple_factory=nt)
        self.assertEqual(t, NT(42, 2))
        self.assertIs(type(t), NT)

    def test_dynamic_class_creation(self):
        cls_dict = {'__annotations__': OrderedDict(x=int, y=int),
                    }

        # Create the class.
        cls = type('C', (), cls_dict)

        # Make it a dataclass.
        cls1 = dataclass(cls)

        self.assertEqual(cls1, cls)
        self.assertEqual(asdict(cls(1, 2)), {'x': 1, 'y': 2})

    def test_dynamic_class_creation_using_field(self):
        cls_dict = {'__annotations__': OrderedDict(x=int, y=int),
                    'y': field(default=5),
                    }

        # Create the class.
        cls = type('C', (), cls_dict)

        # Make it a dataclass.
        cls1 = dataclass(cls)

        self.assertEqual(cls1, cls)
        self.assertEqual(asdict(cls1(1)), {'x': 1, 'y': 5})

    def test_init_in_order(self):
        @dataclass
        class C:
            a: int
            b: int = field()
            c: list = field(default_factory=list, init=False)
            d: list = field(default_factory=list)
            e: int = field(default=4, init=False)
            f: int = 4

        calls = []
        def setattr(self, name, value):
            calls.append((name, value))

        C.__setattr__ = setattr
        c = C(0, 1)
        self.assertEqual(('a', 0), calls[0])
        self.assertEqual(('b', 1), calls[1])
        self.assertEqual(('c', []), calls[2])
        self.assertEqual(('d', []), calls[3])
        self.assertNotIn(('e', 4), calls)
        self.assertEqual(('f', 4), calls[4])

    def test_items_in_dicts(self):
        @dataclass
        class C:
            a: int
            b: list = field(default_factory=list, init=False)
            c: list = field(default_factory=list)
            d: int = field(default=4, init=False)
            e: int = 0

        c = C(0)
        # Class dict
        self.assertNotIn('a', C.__dict__)
        self.assertNotIn('b', C.__dict__)
        self.assertNotIn('c', C.__dict__)
        self.assertIn('d', C.__dict__)
        self.assertEqual(C.d, 4)
        self.assertIn('e', C.__dict__)
        self.assertEqual(C.e, 0)
        # Instance dict
        self.assertIn('a', c.__dict__)
        self.assertEqual(c.a, 0)
        self.assertIn('b', c.__dict__)
        self.assertEqual(c.b, [])
        self.assertIn('c', c.__dict__)
        self.assertEqual(c.c, [])
        self.assertNotIn('d', c.__dict__)
        self.assertIn('e', c.__dict__)
        self.assertEqual(c.e, 0)

    def test_alternate_classmethod_constructor(self):
        # Since __post_init__ can't take params, use a classmethod
        # alternate constructor. This is mostly an example to show how
        # to use this technique.
        @dataclass
        class C:
            x: int
            @classmethod
            def from_file(cls, filename):
                # In a real example, create a new instance
                #  and populate 'x' from contents of a file.
                value_in_file = 20
                return cls(value_in_file)

        self.assertEqual(C.from_file('filename').x, 20)

    def test_field_metadata_default(self):
        # Make sure the default metadata is read-only and of
        #  zero length.
        @dataclass
        class C:
            i: int

        self.assertFalse(fields(C)[0].metadata)
        self.assertEqual(len(fields(C)[0].metadata), 0)
        with self.assertRaisesRegex(TypeError,
                                    'does not support item assignment'):
            fields(C)[0].metadata['test'] = 3

    def test_field_metadata_mapping(self):
        # Make sure only a mapping can be passed as metadata
        #  zero length.
        with self.assertRaises(TypeError):
            @dataclass
            class C:
                i: int = field(metadata=0)

        # Make sure an empty dict works
        @dataclass
        class C:
            i: int = field(metadata={})
        self.assertFalse(fields(C)[0].metadata)
        self.assertEqual(len(fields(C)[0].metadata), 0)
        with self.assertRaisesRegex(TypeError,
                                    'does not support item assignment'):
            fields(C)[0].metadata['test'] = 3

        # Make sure a non-empty dict works.
        @dataclass
        class C:
            i: int = field(metadata={'test': 10, 'bar': '42', 3: 'three'})
        self.assertEqual(len(fields(C)[0].metadata), 3)
        self.assertEqual(fields(C)[0].metadata['test'], 10)
        self.assertEqual(fields(C)[0].metadata['bar'], '42')
        self.assertEqual(fields(C)[0].metadata[3], 'three')
        with self.assertRaises(KeyError):
            # Non-existent key.
            fields(C)[0].metadata['baz']
        with self.assertRaisesRegex(TypeError,
                                    'does not support item assignment'):
            fields(C)[0].metadata['test'] = 3

    def test_field_metadata_custom_mapping(self):
        # Try a custom mapping.
        class SimpleNameSpace:
            def __init__(self, **kw):
                self.__dict__.update(kw)

            def __getitem__(self, item):
                if item == 'xyzzy':
                    return 'plugh'
                return getattr(self, item)

            def __len__(self):
                return self.__dict__.__len__()

        @dataclass
        class C:
            i: int = field(metadata=SimpleNameSpace(a=10))

        self.assertEqual(len(fields(C)[0].metadata), 1)
        self.assertEqual(fields(C)[0].metadata['a'], 10)
        with self.assertRaises(AttributeError):
            fields(C)[0].metadata['b']
        # Make sure we're still talking to our custom mapping.
        self.assertEqual(fields(C)[0].metadata['xyzzy'], 'plugh')

    def test_generic_dataclasses(self):
        T = TypeVar('T')

        @dataclass
        class LabeledBox(Generic[T]):
            content: T
            label: str = '<unknown>'

        box = LabeledBox(42)
        self.assertEqual(box.content, 42)
        self.assertEqual(box.label, '<unknown>')

        # subscripting the resulting class should work, etc.
        Alias = List[LabeledBox[int]]

    def test_generic_extending(self):
        S = TypeVar('S')
        T = TypeVar('T')

        @dataclass
        class Base(Generic[T, S]):
            x: T
            y: S

        @dataclass
        class DataDerived(Base[int, T]):
            new_field: str
        Alias = DataDerived[str]
        c = Alias(0, 'test1', 'test2')
        self.assertEqual(astuple(c), (0, 'test1', 'test2'))

        class NonDataDerived(Base[int, T]):
            def new_method(self):
                return self.y
        Alias = NonDataDerived[float]
        c = Alias(10, 1.0)
        self.assertEqual(c.new_method(), 1.0)

    def test_helper_replace(self):
        @dataclass(frozen=True)
        class C:
            x: int
            y: int

        c = C(1, 2)
        c1 = replace(c, x=3)
        self.assertEqual(c1.x, 3)
        self.assertEqual(c1.y, 2)

    def test_helper_replace_frozen(self):
        @dataclass(frozen=True)
        class C:
            x: int
            y: int
            z: int = field(init=False, default=10)
            t: int = field(init=False, default=100)

        c = C(1, 2)
        c1 = replace(c, x=3)
        self.assertEqual((c.x, c.y, c.z, c.t), (1, 2, 10, 100))
        self.assertEqual((c1.x, c1.y, c1.z, c1.t), (3, 2, 10, 100))


        with self.assertRaisesRegex(ValueError, 'init=False'):
            replace(c, x=3, z=20, t=50)
        with self.assertRaisesRegex(ValueError, 'init=False'):
            replace(c, z=20)
            replace(c, x=3, z=20, t=50)

        # Make sure the result is still frozen.
        with self.assertRaisesRegex(FrozenInstanceError, "cannot assign to field 'x'"):
            c1.x = 3

        # Make sure we can't replace an attribute that doesn't exist,
        #  if we're also replacing one that does exist.  Test this
        #  here, because setting attributes on frozen instances is
        #  handled slightly differently from non-frozen ones.
        with self.assertRaisesRegex(TypeError, r"__init__\(\) got an unexpected "
                                             "keyword argument 'a'"):
            c1 = replace(c, x=20, a=5)

    def test_helper_replace_invalid_field_name(self):
        @dataclass(frozen=True)
        class C:
            x: int
            y: int

        c = C(1, 2)
        with self.assertRaisesRegex(TypeError, r"__init__\(\) got an unexpected "
                                    "keyword argument 'z'"):
            c1 = replace(c, z=3)

    def test_helper_replace_invalid_object(self):
        @dataclass(frozen=True)
        class C:
            x: int
            y: int

        with self.assertRaisesRegex(TypeError, 'dataclass instance'):
            replace(C, x=3)

        with self.assertRaisesRegex(TypeError, 'dataclass instance'):
            replace(0, x=3)

    def test_helper_replace_no_init(self):
        @dataclass
        class C:
            x: int
            y: int = field(init=False, default=10)

        c = C(1)
        c.y = 20

        # Make sure y gets the default value.
        c1 = replace(c, x=5)
        self.assertEqual((c1.x, c1.y), (5, 10))

        # Trying to replace y is an error.
        with self.assertRaisesRegex(ValueError, 'init=False'):
            replace(c, x=2, y=30)
            with self.assertRaisesRegex(ValueError, 'init=False'):
                replace(c, y=30)

    def test_dataclassses_pickleable(self):
        global P, Q, R
        @dataclass
        class P:
            x: int
            y: int = 0
        @dataclass
        class Q:
            x: int
            y: int = field(default=0, init=False)
        @dataclass
        class R:
            x: int
            y: List[int] = field(default_factory=list)
        q = Q(1)
        q.y = 2
        samples = [P(1), P(1, 2), Q(1), q, R(1), R(1, [2, 3, 4])]
        for sample in samples:
            for proto in range(pickle.HIGHEST_PROTOCOL + 1):
                with self.subTest(sample=sample, proto=proto):
                    new_sample = pickle.loads(pickle.dumps(sample, proto))
                    self.assertEqual(sample.x, new_sample.x)
                    self.assertEqual(sample.y, new_sample.y)
                    self.assertIsNot(sample, new_sample)
                    new_sample.x = 42
                    another_new_sample = pickle.loads(pickle.dumps(new_sample, proto))
                    self.assertEqual(new_sample.x, another_new_sample.x)
                    self.assertEqual(sample.y, another_new_sample.y)

    def test_helper_make_dataclass(self):
        C = make_dataclass('C',
                           [('x', int),
                            ('y', int, field(default=5))],
                           namespace={'add_one': lambda self: self.x + 1})
        c = C(10)
        self.assertEqual((c.x, c.y), (10, 5))
        self.assertEqual(c.add_one(), 11)


    def test_helper_make_dataclass_no_mutate_namespace(self):
        # Make sure a provided namespace isn't mutated.
        ns = {}
        C = make_dataclass('C',
                           [('x', int),
                            ('y', int, field(default=5))],
                           namespace=ns)
        self.assertEqual(ns, {})

    def test_helper_make_dataclass_base(self):
        class Base1:
            pass
        class Base2:
            pass
        C = make_dataclass('C',
                           [('x', int)],
                           bases=(Base1, Base2))
        c = C(2)
        self.assertIsInstance(c, C)
        self.assertIsInstance(c, Base1)
        self.assertIsInstance(c, Base2)

    def test_helper_make_dataclass_base_dataclass(self):
        @dataclass
        class Base1:
            x: int
        class Base2:
            pass
        C = make_dataclass('C',
                           [('y', int)],
                           bases=(Base1, Base2))
        with self.assertRaisesRegex(TypeError, 'required positional'):
            c = C(2)
        c = C(1, 2)
        self.assertIsInstance(c, C)
        self.assertIsInstance(c, Base1)
        self.assertIsInstance(c, Base2)

        self.assertEqual((c.x, c.y), (1, 2))

    def test_helper_make_dataclass_init_var(self):
        def post_init(self, y):
            self.x *= y

        C = make_dataclass('C',
                           [('x', int),
                            ('y', InitVar[int]),
                            ],
                           namespace={'__post_init__': post_init},
                           )
        c = C(2, 3)
        self.assertEqual(vars(c), {'x': 6})
        self.assertEqual(len(fields(c)), 1)

    def test_helper_make_dataclass_class_var(self):
        C = make_dataclass('C',
                           [('x', int),
                            ('y', ClassVar[int], 10),
                            ('z', ClassVar[int], field(default=20)),
                            ])
        c = C(1)
        self.assertEqual(vars(c), {'x': 1})
        self.assertEqual(len(fields(c)), 1)
        self.assertEqual(C.y, 10)
        self.assertEqual(C.z, 20)

    def test_helper_make_dataclass_other_params(self):
        C = make_dataclass('C',
                           [('x', int),
                            ('y', ClassVar[int], 10),
                            ('z', ClassVar[int], field(default=20)),
                            ],
                           init=False)
        # Make sure we have a repr, but no init.
        self.assertNotIn('__init__', vars(C))
        self.assertIn('__repr__', vars(C))

        # Make sure random other params don't work.
        with self.assertRaisesRegex(TypeError, 'unexpected keyword argument'):
            C = make_dataclass('C',
                               [],
                               xxinit=False)

    def test_helper_make_dataclass_no_types(self):
        C = make_dataclass('Point', ['x', 'y', 'z'])
        c = C(1, 2, 3)
        self.assertEqual(vars(c), {'x': 1, 'y': 2, 'z': 3})
        self.assertEqual(C.__annotations__, {'x': 'typing.Any',
                                             'y': 'typing.Any',
                                             'z': 'typing.Any'})

        C = make_dataclass('Point', ['x', ('y', int), 'z'])
        c = C(1, 2, 3)
        self.assertEqual(vars(c), {'x': 1, 'y': 2, 'z': 3})
        self.assertEqual(C.__annotations__, {'x': 'typing.Any',
                                             'y': int,
                                             'z': 'typing.Any'})

class TestDocString(unittest.TestCase):
    def assertDocStrEqual(self, a, b):
        # Because 3.6 and 3.7 differ in how inspect.signature work
        #  (see bpo #32108), for the time being just compare them with
        #  whitespace stripped.
        self.assertEqual(a.replace(' ', ''), b.replace(' ', ''))

    def test_existing_docstring_not_overridden(self):
        @dataclass
        class C:
            """Lorem ipsum"""
            x: int

        self.assertEqual(C.__doc__, "Lorem ipsum")

    def test_docstring_no_fields(self):
        @dataclass
        class C:
            pass

        self.assertDocStrEqual(C.__doc__, "C()")

    def test_docstring_one_field(self):
        @dataclass
        class C:
            x: int

        self.assertDocStrEqual(C.__doc__, "C(x:int)")

    def test_docstring_two_fields(self):
        @dataclass
        class C:
            x: int
            y: int

        self.assertDocStrEqual(C.__doc__, "C(x:int, y:int)")

    def test_docstring_three_fields(self):
        @dataclass
        class C:
            x: int
            y: int
            z: str

        self.assertDocStrEqual(C.__doc__, "C(x:int, y:int, z:str)")

    def test_docstring_one_field_with_default(self):
        @dataclass
        class C:
            x: int = 3

        self.assertDocStrEqual(C.__doc__, "C(x:int=3)")

    def test_docstring_one_field_with_default_none(self):
        @dataclass
        class C:
            x: Union[int, type(None)] = None

        self.assertDocStrEqual(C.__doc__, "C(x:Union[int, NoneType]=None)")

    def test_docstring_list_field(self):
        @dataclass
        class C:
            x: List[int]

        self.assertDocStrEqual(C.__doc__, "C(x:List[int])")

    def test_docstring_list_field_with_default_factory(self):
        @dataclass
        class C:
            x: List[int] = field(default_factory=list)

        self.assertDocStrEqual(C.__doc__, "C(x:List[int]=<factory>)")

    def test_docstring_deque_field(self):
        @dataclass
        class C:
            x: deque

        self.assertDocStrEqual(C.__doc__, "C(x:collections.deque)")

    def test_docstring_deque_field_with_default_factory(self):
        @dataclass
        class C:
            x: deque = field(default_factory=deque)

        self.assertDocStrEqual(C.__doc__, "C(x:collections.deque=<factory>)")


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