Detect ClassVars coming from typing_extensions

changelog.d/782.change.rst

@@ -0,0 +1 @@
+``ClassVar``\ s are now also detected if they come from `typing-extensions <https://pypi.org/project/typing-extensions/>`_.

src/attr/_make.py

@@ -41,7 +41,12 @@
 _tuple_property_pat = (
     "    {attr_name} = _attrs_property(_attrs_itemgetter({index}))"
 )
-_classvar_prefixes = ("typing.ClassVar", "t.ClassVar", "ClassVar")
+_classvar_prefixes = (
+    "typing.ClassVar",
+    "t.ClassVar",
+    "ClassVar",
+    "typing_extensions.ClassVar",
+)
 # we don't use a double-underscore prefix because that triggers
 # name mangling when trying to create a slot for the field
 # (when slots=True)

tests/test_annotations.py

@@ -418,6 +418,18 @@ class C:
             foo=typing.Optional[typing.Any],
         )
 
+    @pytest.mark.parametrize("slots", [True, False])
+    def test_typing_extensions_classvar(self, slots):
+        """
+        If ClassVar is coming from typing_extensions, it is recognized too.
+        """
+
+        @attr.s(auto_attribs=True, slots=slots)
+        class C:
+            cls_var: "typing_extensions.ClassVar" = 23  # noqa
+
+        assert_init_annotations(C)
+
     def test_keyword_only_auto_attribs(self):
         """
         `kw_only` propagates to attributes defined via `auto_attribs`.