Implement C Level Timedelta ISO Function; fix JSON usage

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

@@ -116,3 +116,29 @@ npy_datetime PyDateTimeToEpoch(PyDateTime_Date *dt, NPY_DATETIMEUNIT base) {
     npy_datetime npy_dt = npy_datetimestruct_to_datetime(NPY_FR_ns, &dts);
     return NpyDateTimeToEpoch(npy_dt, base);
 }
+
+/* Converts the int64_t representation of a duration to ISO; mutates len */
+char *int64ToIsoDuration(int64_t value, size_t *len) {
+    pandas_timedeltastruct tds;
+    int ret_code;
+
+    pandas_timedelta_to_timedeltastruct(value, NPY_FR_ns, &tds);
+
+    // Max theoretical length of ISO Duration with 64 bit day
+    // as the largest unit is 70 characters + 1 for a null terminator
+    char *result = PyObject_Malloc(71);
+    if (result == NULL) {
+        PyErr_NoMemory();
+        return NULL;
+    }
+
+    ret_code = make_iso_8601_timedelta(&tds, result, len);
+    if (ret_code == -1) {
+        PyErr_SetString(PyExc_ValueError,
+                        "Could not convert timedelta value to string");
+        PyObject_Free(result);
+        return NULL;
+    }
+
+    return result;
+}

pandas/_libs/src/ujson/python/date_conversions.h

@@ -28,4 +28,6 @@ char *PyDateTimeToIso(PyDateTime_Date *obj, NPY_DATETIMEUNIT base, size_t *len);
 // Convert a Python Date/Datetime to Unix epoch with resolution base
 npy_datetime PyDateTimeToEpoch(PyDateTime_Date *dt, NPY_DATETIMEUNIT base);
 
+char *int64ToIsoDuration(int64_t value, size_t *len);
+
 #endif

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

@@ -53,7 +53,6 @@ static PyTypeObject *cls_dataframe;
 static PyTypeObject *cls_series;
 static PyTypeObject *cls_index;
 static PyTypeObject *cls_nat;
-PyObject *cls_timedelta;
 
 npy_int64 get_nat(void) { return NPY_MIN_INT64; }
 
@@ -164,7 +163,6 @@ void *initObjToJSON(void) {
         cls_index = (PyTypeObject *)PyObject_GetAttrString(mod_pandas, "Index");
         cls_series =
             (PyTypeObject *)PyObject_GetAttrString(mod_pandas, "Series");
-        cls_timedelta = PyObject_GetAttrString(mod_pandas, "Timedelta");
         Py_DECREF(mod_pandas);
     }
 
@@ -357,6 +355,12 @@ static char *NpyDateTimeToIsoCallback(JSOBJ Py_UNUSED(unused),
     return int64ToIso(GET_TC(tc)->longValue, base, len);
 }
 
+/* JSON callback. returns a char* and mutates the pointer to *len */
+static char *NpyTimeDeltaToIsoCallback(JSOBJ Py_UNUSED(unused),
+                                       JSONTypeContext *tc, size_t *len) {
+    return int64ToIsoDuration(GET_TC(tc)->longValue, len);
+}
+
 /* JSON callback */
 static char *PyDateTimeToIsoCallback(JSOBJ obj, JSONTypeContext *tc,
                                      size_t *len) {
@@ -1445,7 +1449,8 @@ char **NpyArr_encodeLabels(PyArrayObject *labels, PyObjectEncoder *enc,
                                  1000000000LL; // nanoseconds per second
                 } else {
                     // datetime.* objects don't follow above rules
-                    nanosecVal = PyDateTimeToEpoch(item, NPY_FR_ns);
+                    nanosecVal =
+                        PyDateTimeToEpoch((PyDateTime_Date *)item, NPY_FR_ns);
                 }
             }
         }
@@ -1457,31 +1462,8 @@ char **NpyArr_encodeLabels(PyArrayObject *labels, PyObjectEncoder *enc,
                 strncpy(cLabel, "null", len);
             } else {
                 if (enc->datetimeIso) {
-                    // TODO: Vectorized Timedelta function
                     if ((type_num == NPY_TIMEDELTA) || (PyDelta_Check(item))) {
-                        PyObject *td =
-                            PyObject_CallFunction(cls_timedelta, "(O)", item);
-                        if (td == NULL) {
-                            Py_DECREF(item);
-                            NpyArr_freeLabels(ret, num);
-                            ret = 0;
-                            break;
-                        }
-
-                        PyObject *iso =
-                            PyObject_CallMethod(td, "isoformat", NULL);
-                        Py_DECREF(td);
-                        if (iso == NULL) {
-                            Py_DECREF(item);
-                            NpyArr_freeLabels(ret, num);
-                            ret = 0;
-                            break;
-                        }
-
-                        len = strlen(PyUnicode_AsUTF8(iso));
-                        cLabel = PyObject_Malloc(len + 1);
-                        memcpy(cLabel, PyUnicode_AsUTF8(iso), len + 1);
-                        Py_DECREF(iso);
+                        cLabel = int64ToIsoDuration(nanosecVal, &len);
                     } else {
                         if (type_num == NPY_DATETIME) {
                             cLabel = int64ToIso(nanosecVal, base, &len);
@@ -1614,7 +1596,11 @@ void Object_beginTypeContext(JSOBJ _obj, JSONTypeContext *tc) {
 
             if (enc->datetimeIso) {
                 PRINTMARK();
-                pc->PyTypeToUTF8 = NpyDateTimeToIsoCallback;
+                if (enc->npyType == NPY_TIMEDELTA) {
+                    pc->PyTypeToUTF8 = NpyTimeDeltaToIsoCallback;
+                } else {
+                    pc->PyTypeToUTF8 = NpyDateTimeToIsoCallback;
+                }
                 // Currently no way to pass longVal to iso function, so use
                 // state management
                 GET_TC(tc)->longValue = longVal;
@@ -1695,7 +1681,8 @@ void Object_beginTypeContext(JSOBJ _obj, JSONTypeContext *tc) {
             PRINTMARK();
             NPY_DATETIMEUNIT base =
                 ((PyObjectEncoder *)tc->encoder)->datetimeUnit;
-            GET_TC(tc)->longValue = PyDateTimeToEpoch((PyDateTime_Date *)obj, base);
+            GET_TC(tc)->longValue =
+                PyDateTimeToEpoch((PyDateTime_Date *)obj, base);
             tc->type = JT_LONG;
         }
         return;
@@ -1721,7 +1708,8 @@ void Object_beginTypeContext(JSOBJ _obj, JSONTypeContext *tc) {
             PRINTMARK();
             NPY_DATETIMEUNIT base =
                 ((PyObjectEncoder *)tc->encoder)->datetimeUnit;
-            GET_TC(tc)->longValue = PyDateTimeToEpoch((PyDateTime_Date *)obj, base);
+            GET_TC(tc)->longValue =
+                PyDateTimeToEpoch((PyDateTime_Date *)obj, base);
             tc->type = JT_LONG;
         }
         return;
@@ -1734,28 +1722,30 @@ void Object_beginTypeContext(JSOBJ _obj, JSONTypeContext *tc) {
             value = total_seconds(obj) * 1000000000LL; // nanoseconds per second
         }
 
-        unit = ((PyObjectEncoder *)tc->encoder)->datetimeUnit;
-        if (scaleNanosecToUnit(&value, unit) != 0) {
-            // TODO: Add some kind of error handling here
-        }
-
-        exc = PyErr_Occurred();
-
-        if (exc && PyErr_ExceptionMatches(PyExc_OverflowError)) {
-            PRINTMARK();
-            goto INVALID;
-        }
-
+        PRINTMARK();
         if (value == get_nat()) {
             PRINTMARK();
             tc->type = JT_NULL;
             return;
-        }
+        } else if (enc->datetimeIso) {
+            pc->PyTypeToUTF8 = NpyTimeDeltaToIsoCallback;
+            tc->type = JT_UTF8;
+        } else {
+            unit = ((PyObjectEncoder *)tc->encoder)->datetimeUnit;
+            if (scaleNanosecToUnit(&value, unit) != 0) {
+                // TODO: Add some kind of error handling here
+            }
 
-        GET_TC(tc)->longValue = value;
+            exc = PyErr_Occurred();
 
-        PRINTMARK();
-        tc->type = JT_LONG;
+            if (exc && PyErr_ExceptionMatches(PyExc_OverflowError)) {
+                PRINTMARK();
+                goto INVALID;
+            }
+
+            tc->type = JT_LONG;
+        }
+        GET_TC(tc)->longValue = value;
         return;
     } else if (PyArray_IsScalar(obj, Integer)) {
         PRINTMARK();

pandas/_libs/tslibs/src/datetime/np_datetime_strings.c

@@ -905,3 +905,37 @@ int make_iso_8601_datetime(npy_datetimestruct *dts, char *outstr, int outlen,
                  outlen);
     return -1;
 }
+
+
+int make_iso_8601_timedelta(pandas_timedeltastruct *tds,
+                            char *outstr, size_t *outlen) {
+  *outlen = 0;
+  *outlen += snprintf(outstr, 60,  // NOLINT
+                     "P%" NPY_INT64_FMT
+                     "DT%" NPY_INT32_FMT
+                     "H%" NPY_INT32_FMT
+                     "M%" NPY_INT32_FMT,
+                     tds->days, tds->hrs, tds->min, tds->sec);
+  outstr += *outlen;
+
+  if (tds->ns != 0) {
+    *outlen += snprintf(outstr, 12,  // NOLINT
+                       ".%03" NPY_INT32_FMT
+                       "%03" NPY_INT32_FMT
+                       "%03" NPY_INT32_FMT
+                       "S", tds->ms, tds->us, tds->ns);
+  } else if (tds->us != 0) {
+    *outlen += snprintf(outstr, 9,  // NOLINT
+                       ".%03" NPY_INT32_FMT
+                       "%03" NPY_INT32_FMT
+                       "S", tds->ms, tds->us);
+  } else if (tds->ms != 0) {
+    *outlen += snprintf(outstr, 6,  // NOLINT
+                        ".%03" NPY_INT32_FMT "S", tds->ms);
+  } else {
+    *outlen += snprintf(outstr, 2,  // NOLINT
+                        "%s", "S");
+  }
+
+  return 0;
+}

pandas/_libs/tslibs/src/datetime/np_datetime_strings.h

@@ -79,4 +79,14 @@ get_datetime_iso_8601_strlen(int local, NPY_DATETIMEUNIT base);
 int
 make_iso_8601_datetime(npy_datetimestruct *dts, char *outstr, int outlen,
                        NPY_DATETIMEUNIT base);
+
+/*
+ * Converts an pandas_timedeltastruct to an ISO 8601 string.
+ *
+ * Mutates outlen to provide size of (non-NULL terminated) string.
+ *
+ * Returns NULL on error.
+ */
+int make_iso_8601_timedelta(pandas_timedeltastruct *tds, char *outstr,
+                            size_t *outlen);
 #endif  // PANDAS__LIBS_TSLIBS_SRC_DATETIME_NP_DATETIME_STRINGS_H_

pandas/tests/io/json/test_json_table_schema.py

@@ -603,8 +603,7 @@ def test_timestamp_in_columns(self):
         result = df.to_json(orient="table")
         js = json.loads(result)
         assert js["schema"]["fields"][1]["name"] == "2016-01-01T00:00:00.000Z"
-        # TODO - below expectation is not correct; see GH 28256
-        assert js["schema"]["fields"][2]["name"] == 10000
+        assert js["schema"]["fields"][2]["name"] == "P0DT0H0M10S"
 
     @pytest.mark.parametrize(
         "case",

pandas/tests/io/json/test_pandas.py

@@ -1058,6 +1058,29 @@ def test_mixed_timedelta_datetime(self):
         result = pd.read_json(frame.to_json(date_unit="ns"), dtype={"a": "int64"})
         tm.assert_frame_equal(result, expected, check_index_type=False)
 
+    @pytest.mark.parametrize("as_object", [True, False])
+    @pytest.mark.parametrize("date_format", ["iso", "epoch"])
+    @pytest.mark.parametrize("timedelta_typ", [pd.Timedelta, timedelta])
+    def test_timedelta_to_json(self, as_object, date_format, timedelta_typ):
+        # GH28156: to_json not correctly formatting Timedelta
+        data = [timedelta_typ(days=1), timedelta_typ(days=2), pd.NaT]
+        if as_object:
+            data.append("a")
+
+        ser = pd.Series(data, index=data)
+        if date_format == "iso":
+            expected = (
+                '{"P1DT0H0M0S":"P1DT0H0M0S","P2DT0H0M0S":"P2DT0H0M0S","null":null}'
+            )
+        else:
+            expected = '{"86400000":86400000,"172800000":172800000,"null":null}'
+
+        if as_object:
+            expected = expected.replace("}", ',"a":"a"}')
+
+        result = ser.to_json(date_format=date_format)
+        assert result == expected
+
     def test_default_handler(self):
         value = object()
         frame = DataFrame({"a": [7, value]})