Convert dates to datetimes for DateHourParameter (#2285)

luigi/parameter.py

@@ -479,6 +479,12 @@ def serialize(self, dt):
             return str(dt)
         return dt.strftime(self.date_format)
 
+    @staticmethod
+    def _convert_to_dt(dt):
+        if not isinstance(dt, datetime.datetime):
+            dt = datetime.datetime.combine(dt, datetime.time.min)
+        return dt
+
     def normalize(self, dt):
         """
         Clamp dt to every Nth :py:attr:`~_DatetimeParameterBase.interval` starting at
@@ -487,6 +493,8 @@ def normalize(self, dt):
         if dt is None:
             return None
 
+        dt = self._convert_to_dt(dt)
+
         dt = dt.replace(microsecond=0)  # remove microseconds, to avoid float rounding issues.
         delta = (dt - self.start).total_seconds()
         granularity = (self._timedelta * self.interval).total_seconds()

test/date_parameter_test.py

@@ -70,6 +70,10 @@ def test_parse(self):
         dh = luigi.DateHourParameter().parse('2013-02-01T18')
         self.assertEqual(dh, datetime.datetime(2013, 2, 1, 18, 0, 0))
 
+    def test_date_to_dh(self):
+        date = luigi.DateHourParameter().normalize(datetime.date(2000, 1, 1))
+        self.assertEqual(date, datetime.datetime(2000, 1, 1, 0))
+
     def test_serialize(self):
         dh = luigi.DateHourParameter().serialize(datetime.datetime(2013, 2, 1, 18, 0, 0))
         self.assertEqual(dh, '2013-02-01T18')