Fix calling of callable object when binding was attempted.

docs/changes.rst

@@ -16,6 +16,12 @@ Note that version 1.17.0 drops support for Python 3.6 and 3.7. Python version
   or instance. This was not the correct behaviour and the class or instance
   should not have been passed as the first argument.
 
+* When an instance of a callable class object was wrapped which didn't not have
+  a `__get__()` method for binding, and it was called in context whhere binding
+  would be attempted, it would fail with error that `__get__()` did not exist
+  when instead it should have been called directly, ignoring that binding was
+  not possible. 
+
 Version 1.16.0
 --------------
 

src/wrapt/_wrappers.c

@@ -2488,10 +2488,8 @@ static PyObject *WraptFunctionWrapperBase_descr_get(
         }
 
         if (Py_TYPE(self->object_proxy.wrapped)->tp_descr_get == NULL) {
-            PyErr_Format(PyExc_AttributeError,
-                    "'%s' object has no attribute '__get__'",
-                    Py_TYPE(self->object_proxy.wrapped)->tp_name);
-            return NULL;
+            Py_INCREF(self);
+            return (PyObject *)self;
         }
 
         descriptor = (Py_TYPE(self->object_proxy.wrapped)->tp_descr_get)(

src/wrapt/wrappers.py

@@ -528,13 +528,21 @@ def __get__(self, instance, owner):
         # extract the instance from the first argument of those passed in.
 
         if self._self_parent is None:
+            # Technically can probably just check for existence of __get__ on
+            # the wrapped object, but this is more explicit.
+
             if self._self_binding == 'builtin':
                 return self
 
             if self._self_binding == "class":
                 return self
 
-            descriptor = self.__wrapped__.__get__(instance, owner)
+            binder = getattr(self.__wrapped__, '__get__', None)
+
+            if binder is None:
+                return self
+
+            descriptor =  binder(instance, owner)
 
             return self.__bound_function_wrapper__(descriptor, instance,
                     self._self_wrapper, self._self_enabled,

tests/test_decorators.py

@@ -297,5 +297,43 @@ class C13:
         C11.f1(c11)
         C12.f2(c12)
 
+    def test_call_semantics_for_assorted_wrapped_descriptor_use_cases(self):
+        class A:
+            def __call__(self):
+                print("A:__call__")
+
+        a = A()
+
+        class B:
+            def __call__(self):
+                print("B:__call__")
+            def __get__(self, obj, type):
+                print("B:__get__")
+                return self
+
+        b = B()
+
+        class C:
+            f1 = a
+            f2 = b
+
+        c = C()
+
+        c.f1()
+        c.f2()
+
+        @wrapt.decorator
+        def wrapper(wrapped, instance, args, kwargs):
+            return wrapped(*args, **kwargs)
+
+        class D:
+            f1 = wrapper(a)
+            f2 = wrapper(b)
+
+        d = D()
+
+        d.f1()
+        d.f2()
+
 if __name__ == '__main__':
     unittest.main()

tests/test_function_wrapper.py

@@ -554,7 +554,7 @@ def _wrapper(wrapped, instance, args, kwargs):
             wrapper = wrapt.FunctionWrapper(None, _wrapper)
             wrapper.__get__(list(), list)()
 
-        self.assertRaises(AttributeError, run, ())
+        self.assertRaises(TypeError, run, ())
 
 class TestInvalidCalling(unittest.TestCase):