Fix issue with patching staticmethod w/ staticmethod

Summary: Fixes a small issue I noticed while working on D52525922.  When we go to handle a value being patched we don't do the unwrapping of the static/class method.  So this moves that logic into `update_thunk` and moves the `_PyClassLoader_ResolveFunction` unwrapping to only happen in the case where we're not returning a thunk.

Reviewed By: carljm

Differential Revision: D52527349

fbshipit-source-id: fbe49c2ced72c68b1467a607ad20a2987c90c36c

cinderx/StaticPython/classloader.c

@@ -2807,8 +2807,13 @@ update_thunk(_Py_StaticThunk *thunk, PyObject *previous, PyObject *new_value)
 {
     Py_CLEAR(thunk->thunk_tcs.tcs_value);
     if (new_value != NULL) {
-        thunk->thunk_tcs.tcs_value = new_value;
-        Py_INCREF(new_value);
+        PyObject *unwrapped_new = classloader_maybe_unwrap_callable(new_value);
+        if (unwrapped_new != NULL) {
+            thunk->thunk_tcs.tcs_value = unwrapped_new;
+        } else {
+            thunk->thunk_tcs.tcs_value = new_value;
+            Py_INCREF(new_value);
+        }
     }
     PyObject *funcref;
     if (new_value == previous) {
@@ -4258,6 +4263,13 @@ _PyClassLoader_ResolveFunction(PyObject *path, PyObject **container)
         original = NULL;
     }
 
+    if (original != NULL) {
+        PyObject *res = (PyObject *)get_or_make_thunk(func, original, *container, containerkey);
+        Py_DECREF(func);
+        assert(res != NULL);
+        return res;
+    }
+
     if (func != NULL) {
         if (Py_TYPE(func) == &PyStaticMethod_Type) {
             PyObject *res = Ci_PyStaticMethod_GetFunc(func);
@@ -4273,13 +4285,6 @@ _PyClassLoader_ResolveFunction(PyObject *path, PyObject **container)
         }
     }
 
-    if (original != NULL) {
-        PyObject *res = (PyObject *)get_or_make_thunk(func, original, *container, containerkey);
-        Py_DECREF(func);
-        assert(res != NULL);
-        return res;
-    }
-
     return func;
 }
 

cinderx/test_cinderx/test_compiler/test_static/patch.py

@@ -257,6 +257,28 @@ def g():
             with patch(f"{mod.__name__}.C.f", autospec=True, return_value=100) as p:
                 self.assertEqual(g(), 100)
 
+    def test_patch_staticmethod_with_staticmethod(self):
+        codestr = """
+            class C:
+                @staticmethod
+                def f():
+                    return 42
+
+            def g():
+                return C.f()
+        """
+        with self.in_module(codestr) as mod:
+            g = mod.g
+            for i in range(100):
+                self.assertEqual(g(), 42)
+
+            @staticmethod
+            def new():
+                return 100
+
+            mod.C.f = new
+            self.assertEqual(g(), 100)
+
     def test_patch_static_function_non_autospec(self):
         codestr = """
             class C: