BUG: core: allow scalar type richcompare to call ndarray-subclass met…

…hods

This makes the scalar richcmp behave exactly as
"array(self) <op> other". The difference comes in when "other" is an ndarray
subclass, in which case this change allows the subclass to override the
comparison operations via usual Python binop dispatch rules.

numpy/core/src/multiarray/scalartypes.c.src

@@ -1082,7 +1082,11 @@ gentype_richcompare(PyObject *self, PyObject *other, int cmp_op)
     if (arr == NULL) {
         return NULL;
     }
-    ret = Py_TYPE(arr)->tp_richcompare(arr, other, cmp_op);
+    /*
+     * Call via PyObject_RichCompare to ensure that other.__eq__
+     * has a chance to run when necessary
+     */
+    ret = PyObject_RichCompare(arr, other, cmp_op);
     Py_DECREF(arr);
     return ret;
 }

numpy/core/tests/test_regression.py

@@ -1993,6 +1993,16 @@ def __array__(self,*args,**kwargs):
         assert_(not op.eq(lhs, rhs))
         assert_(op.ne(lhs, rhs))
 
+    def test_richcompare_scalar_and_subclass(self):
+        # gh-4709
+        class Foo(np.ndarray):
+            def __eq__(self, other):
+                return "OK"
+        x = np.array([1,2,3]).view(Foo)
+        assert_equal(10 == x, "OK")
+        assert_equal(np.int32(10) == x, "OK")
+        assert_equal(np.array([10]) == x, "OK")
+
 
 if __name__ == "__main__":
     run_module_suite()