Don't trust descriptors to return themselves. Fixes #1122.

ci-requirements.txt

@@ -22,6 +22,8 @@ dnspython
 idna
 # Makes tests faster
 psutil
+# Used in a test
+zope.interface
 # For viewing README.rst (restview --long-description),
 # CONTRIBUTING.rst, etc.
 # https://github.com/mgedmin/restview

src/gevent/_local.pxd

@@ -102,6 +102,9 @@ cdef inline dict _local_get_dict(local self)
 @cython.locals(entry=_localimpl_dict_entry)
 cdef _local__copy_dict_from(local self, _localimpl impl, dict duplicate)
 
+@cython.locals(mro=list, base=type, gets=set, dels=set, set_or_del=set,
+               type_self=type, type_attr=type,
+               sets=set)
 cdef tuple _local_find_descriptors(local self)
 
 @cython.locals(result=list, local_impl=_localimpl,

src/gevent/local.py

@@ -531,9 +531,21 @@ def _local_find_descriptors(self):
     dels = set()
     set_or_del = set()
     sets = set()
+    mro = list(type_self.mro())
 
     for attr_name in dir(type_self):
-        attr = getattr(type_self, attr_name)
+        # Conventionally, descriptors when called on a class
+        # return themself, but not all do. Notable exceptions are
+        # in the zope.interface package, where things like __provides__
+        # return other class attributes. So we can't use getattr, and instead
+        # walk up the dicts
+        for base in mro:
+            if attr_name in base.__dict__:
+                attr = base.__dict__[attr_name]
+                break
+        else:
+            raise AttributeError(attr_name)
+
         type_attr = type(attr)
         if hasattr(type_attr, '__get__'):
             gets.add(attr_name)

src/greentest/test__local.py

@@ -68,7 +68,7 @@ class WithGetattr(local):
             return 42
         return super(WithGetattr, self).__getattr__(name)
 
-class GeventLocalTestCase(greentest.TestCase):
+class TestGeventLocal(greentest.TestCase):
     # pylint:disable=attribute-defined-outside-init,blacklisted-name
 
     def setUp(self):
@@ -323,6 +323,36 @@ class GeventLocalTestCase(greentest.TestCase):
         self.assertEqual(results,
                          [((MyLocal, id(x)), {'foo': 42})])
 
+try:
+    from zope import interface
+except ImportError:
+    interface = None
+
+@greentest.skipIf(interface is None, "Needs zope.interface")
+class TestLocalInterface(greentest.TestCase):
+    __timeout__ = None
+
+    @greentest.ignores_leakcheck
+    def test_provides(self):
+        # https://github.com/gevent/gevent/issues/1122
+
+        # pylint:disable=inherit-non-class
+        class IFoo(interface.Interface):
+            pass
+
+        @interface.implementer(IFoo)
+        class Base(object):
+            pass
+
+        class Derived(Base, local):
+            pass
+
+        d = Derived()
+        p = list(interface.providedBy(d))
+        self.assertEqual([IFoo], p)
+
+
+
 @greentest.skipOnPurePython("Needs C extension")
 class TestCExt(greentest.TestCase):