BUG: fix broken error message in ujson.encode() (GH18878) (pandas-dev#28666)

Author: rlamy

doc/source/whatsnew/v1.0.0.rst

@@ -358,6 +358,7 @@ Other
 - :meth:`DataFrame.to_csv` and :meth:`Series.to_csv` now support dicts as ``compression`` argument with key ``'method'`` being the compression method and others as additional compression options when the compression method is ``'zip'``. (:issue:`26023`)
 - Bug in :meth:`Series.diff` where a boolean series would incorrectly raise a ``TypeError`` (:issue:`17294`)
 - :meth:`Series.append` will no longer raise a ``TypeError`` when passed a tuple of ``Series`` (:issue:`28410`)
+- Fix corrupted error message when calling ``pandas.libs._json.encode()`` on a 0d array (:issue:`18878`)
 
 .. _whatsnew_1000.contributors:
 

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

@@ -780,7 +780,9 @@ def test_array_float(self):
         tm.assert_almost_equal(arr, arr_out)
 
     def test_0d_array(self):
-        with pytest.raises(TypeError):
+        # gh-18878
+        msg = re.escape("array(1) (0d array) is not JSON serializable at the moment")
+        with pytest.raises(TypeError, match=msg):
             ujson.encode(np.array(1))
 
     @pytest.mark.parametrize(