BUG: fix broken error message in ujson.encode() (GH18878)

Author: rlamy

pandas/_libs/src/ujson/python/objToJSON.c

@@ -1986,11 +1986,9 @@ void Object_beginTypeContext(JSOBJ _obj, JSONTypeContext *tc) {
         tc->type = JT_DOUBLE;
         return;
     } else if (PyArray_Check(obj) && PyArray_CheckScalar(obj)) {
-        tmpObj = PyObject_Repr(obj);
         PyErr_Format(PyExc_TypeError,
-                     "%s (0d array) is not JSON serializable at the moment",
-                     PyBytes_AS_STRING(tmpObj));
-        Py_DECREF(tmpObj);
+                     "%R (0d array) is not JSON serializable at the moment",
+                     obj);
         goto INVALID;
     }
 

pandas/tests/io/json/test_ujson.py

@@ -780,8 +780,10 @@ def test_array_float(self):
         tm.assert_almost_equal(arr, arr_out)
 
     def test_0d_array(self):
-        with pytest.raises(TypeError):
+        msg = "array(1) (0d array) is not JSON serializable at the moment"
+        with pytest.raises(TypeError) as excinfo:
             ujson.encode(np.array(1))
+        assert str(excinfo.value) == msg
 
     @pytest.mark.parametrize(
         "bad_input,exc_type,kwargs",