Copy ClassVar upstream (#280)

With some refactoring to avoid depending on core test infrastructure.

python2/test_typing.py

@@ -12,7 +12,7 @@
 from typing import Union, Optional
 from typing import Tuple
 from typing import Callable
-from typing import Generic
+from typing import Generic, ClassVar
 from typing import cast
 from typing import Type
 from typing import NewType
@@ -802,6 +802,43 @@ class D(C):
         with self.assertRaises(Exception):
             D[T]
 
+class ClassVarTests(BaseTestCase):
+
+    def test_basics(self):
+        with self.assertRaises(TypeError):
+            ClassVar[1]
+        with self.assertRaises(TypeError):
+            ClassVar[int, str]
+        with self.assertRaises(TypeError):
+            ClassVar[int][str]
+
+    def test_repr(self):
+        self.assertEqual(repr(ClassVar), 'typing.ClassVar')
+        cv = ClassVar[int]
+        self.assertEqual(repr(cv), 'typing.ClassVar[int]')
+        cv = ClassVar[Employee]
+        self.assertEqual(repr(cv), 'typing.ClassVar[%s.Employee]' % __name__)
+
+    def test_cannot_subclass(self):
+        with self.assertRaises(TypeError):
+            class C(type(ClassVar)):
+                pass
+        with self.assertRaises(TypeError):
+            class C(type(ClassVar[int])):
+                pass
+
+    def test_cannot_init(self):
+        with self.assertRaises(TypeError):
+            type(ClassVar)()
+        with self.assertRaises(TypeError):
+            type(ClassVar[Optional[int]])()
+
+    def test_no_isinstance(self):
+        with self.assertRaises(TypeError):
+            isinstance(1, ClassVar[int])
+        with self.assertRaises(TypeError):
+            issubclass(int, ClassVar)
+
 
 class VarianceTests(BaseTestCase):
 

python2/typing.py

@@ -18,6 +18,7 @@
     # Super-special typing primitives.
     'Any',
     'Callable',
+    'ClassVar',
     'Generic',
     'Optional',
     'Tuple',
@@ -265,7 +266,7 @@ def __subclasscheck__(self, cls):
 
 def _get_type_vars(types, tvars):
     for t in types:
-        if isinstance(t, TypingMeta):
+        if isinstance(t, TypingMeta) or isinstance(t, _ClassVar):
             t._get_type_vars(tvars)
 
 
@@ -276,7 +277,7 @@ def _type_vars(types):
 
 
 def _eval_type(t, globalns, localns):
-    if isinstance(t, TypingMeta):
+    if isinstance(t, TypingMeta) or isinstance(t, _ClassVar):
         return t._eval_type(globalns, localns)
     else:
         return t
@@ -320,6 +321,78 @@ def _type_repr(obj):
         return repr(obj)
 
 
+class ClassVarMeta(TypingMeta):
+    """Metaclass for _ClassVar"""
+
+    def __new__(cls, name, bases, namespace):
+        cls.assert_no_subclassing(bases)
+        self = super(ClassVarMeta, cls).__new__(cls, name, bases, namespace)
+        return self
+
+
+class _ClassVar(object):
+    """Special type construct to mark class variables.
+
+    An annotation wrapped in ClassVar indicates that a given
+    attribute is intended to be used as a class variable and
+    should not be set on instances of that class. Usage::
+
+      class Starship:
+          stats = {}  # type: ClassVar[Dict[str, int]] # class variable
+          damage = 10 # type: int                      # instance variable
+
+    ClassVar accepts only types and cannot be further subscribed.
+
+    Note that ClassVar is not a class itself, and should not
+    be used with isinstance() or issubclass().
+    """
+
+    __metaclass__ = ClassVarMeta
+
+    def __init__(self, tp=None, _root=False):
+        cls = type(self)
+        if _root:
+            self.__type__ = tp
+        else:
+            raise TypeError('Cannot initialize {}'.format(cls.__name__[1:]))
+
+    def __getitem__(self, item):
+        cls = type(self)
+        if self.__type__ is None:
+            return cls(_type_check(item,
+                       '{} accepts only types.'.format(cls.__name__[1:])),
+                       _root=True)
+        raise TypeError('{} cannot be further subscripted'
+                        .format(cls.__name__[1:]))
+
+    def _eval_type(self, globalns, localns):
+        return type(self)(_eval_type(self.__type__, globalns, localns),
+                          _root=True)
+
+    def _get_type_vars(self, tvars):
+        if self.__type__:
+            _get_type_vars(self.__type__, tvars)
+
+    def __repr__(self):
+        cls = type(self)
+        if not self.__type__:
+            return '{}.{}'.format(cls.__module__, cls.__name__[1:])
+        return '{}.{}[{}]'.format(cls.__module__, cls.__name__[1:],
+                                  _type_repr(self.__type__))
+
+    def __hash__(self):
+        return hash((type(self).__name__, self.__type__))
+
+    def __eq__(self, other):
+        if not isinstance(other, _ClassVar):
+            return NotImplemented
+        if self.__type__ is not None:
+            return self.__type__ == other.__type__
+        return self is other
+
+ClassVar = _ClassVar(_root=True)
+
+
 class AnyMeta(TypingMeta):
     """Metaclass for Any."""
 

src/test_typing.py

@@ -9,9 +9,9 @@
 from typing import TypeVar, AnyStr
 from typing import T, KT, VT  # Not in __all__.
 from typing import Union, Optional
-from typing import Tuple
+from typing import Tuple, List
 from typing import Callable
-from typing import Generic
+from typing import Generic, ClassVar
 from typing import cast
 from typing import get_type_hints
 from typing import no_type_check, no_type_check_decorator
@@ -827,6 +827,43 @@ class D(C):
         with self.assertRaises(Exception):
             D[T]
 
+class ClassVarTests(BaseTestCase):
+
+    def test_basics(self):
+        with self.assertRaises(TypeError):
+            ClassVar[1]
+        with self.assertRaises(TypeError):
+            ClassVar[int, str]
+        with self.assertRaises(TypeError):
+            ClassVar[int][str]
+
+    def test_repr(self):
+        self.assertEqual(repr(ClassVar), 'typing.ClassVar')
+        cv = ClassVar[int]
+        self.assertEqual(repr(cv), 'typing.ClassVar[int]')
+        cv = ClassVar[Employee]
+        self.assertEqual(repr(cv), 'typing.ClassVar[%s.Employee]' % __name__)
+
+    def test_cannot_subclass(self):
+        with self.assertRaises(TypeError):
+            class C(type(ClassVar)):
+                pass
+        with self.assertRaises(TypeError):
+            class C(type(ClassVar[int])):
+                pass
+
+    def test_cannot_init(self):
+        with self.assertRaises(TypeError):
+            type(ClassVar)()
+        with self.assertRaises(TypeError):
+            type(ClassVar[Optional[int]])()
+
+    def test_no_isinstance(self):
+        with self.assertRaises(TypeError):
+            isinstance(1, ClassVar[int])
+        with self.assertRaises(TypeError):
+            issubclass(int, ClassVar)
+
 
 class VarianceTests(BaseTestCase):
 
@@ -1119,6 +1156,68 @@ def __anext__(self) -> T_a:
 if PY35:
     exec(PY35_TESTS)
 
+PY36 = sys.version_info[:2] >= (3, 6)
+
+PY36_TESTS = """
+from test import ann_module, ann_module2, ann_module3
+from collections import ChainMap
+
+class B:
+    x: ClassVar[Optional['B']] = None
+    y: int
+class CSub(B):
+    z: ClassVar['CSub'] = B()
+class G(Generic[T]):
+    lst: ClassVar[List[T]] = []
+"""
+
+if PY36:
+    exec(PY36_TESTS)
+
+gth = get_type_hints
+
+class GetTypeHintTests(BaseTestCase):
+    @skipUnless(PY36, 'Python 3.6 required')
+    def test_get_type_hints_modules(self):
+        self.assertEqual(gth(ann_module), {'x': int, 'y': str})
+        self.assertEqual(gth(ann_module2), {})
+        self.assertEqual(gth(ann_module3), {})
+
+    @skipUnless(PY36, 'Python 3.6 required')
+    def test_get_type_hints_classes(self):
+        self.assertEqual(gth(ann_module.C, ann_module.__dict__),
+                         ChainMap({'y': Optional[ann_module.C]}, {}))
+        self.assertEqual(repr(gth(ann_module.j_class)), 'ChainMap({}, {})')
+        self.assertEqual(gth(ann_module.M), ChainMap({'123': 123, 'o': type},
+                                                     {}, {}))
+        self.assertEqual(gth(ann_module.D),
+                         ChainMap({'j': str, 'k': str,
+                                   'y': Optional[ann_module.C]}, {}))
+        self.assertEqual(gth(ann_module.Y), ChainMap({'z': int}, {}))
+        self.assertEqual(gth(ann_module.h_class),
+                         ChainMap({}, {'y': Optional[ann_module.C]}, {}))
+        self.assertEqual(gth(ann_module.S), ChainMap({'x': str, 'y': str},
+                                                     {}))
+        self.assertEqual(gth(ann_module.foo), {'x': int})
+
+    @skipUnless(PY36, 'Python 3.6 required')
+    def test_respect_no_type_check(self):
+        self.assertEqual(gth(ann_module2.NTC.meth), {})
+
+    def test_previous_behavior(self):
+        def testf(x, y): ...
+        testf.__annotations__['x'] = 'int'
+        self.assertEqual(gth(testf), {'x': int})
+
+    @skipUnless(PY36, 'Python 3.6 required')
+    def test_get_type_hints_ClassVar(self):
+        self.assertEqual(gth(B, globals()),
+                         ChainMap({'y': int, 'x': ClassVar[Optional[B]]}, {}))
+        self.assertEqual(gth(CSub, globals()),
+                         ChainMap({'z': ClassVar[CSub]},
+                                  {'y': int, 'x': ClassVar[Optional[B]]}, {}))
+        self.assertEqual(gth(G), ChainMap({'lst': ClassVar[List[T]]},{},{}))
+
 
 class CollectionsAbcTests(BaseTestCase):