fix: time parser truncate to first day of year/month (#14945)

superset/utils/date_parser.py

@@ -79,7 +79,8 @@ def parse_human_datetime(human_readable: str) -> datetime:
     if re.search(x_periods, human_readable, re.IGNORECASE):
         raise TimeRangeUnclearError(human_readable)
     try:
-        dttm = parse(human_readable)
+        default = datetime(year=datetime.now().year, month=1, day=1)
+        dttm = parse(human_readable, default=default)
     except (ValueError, OverflowError) as ex:
         cal = parsedatetime.Calendar()
         parsed_dttm, parsed_flags = cal.parseDT(human_readable)

tests/utils/date_parser_tests.py

@@ -35,6 +35,10 @@
 def mock_parse_human_datetime(s):
     if s == "now":
         return datetime(2016, 11, 7, 9, 30, 10)
+    elif s == "2018":
+        return datetime(2018, 1, 1)
+    elif s == "2018-9":
+        return datetime(2018, 9, 1)
     elif s == "today":
         return datetime(2016, 11, 7)
     elif s == "yesterday":
@@ -153,6 +157,14 @@ def test_datetime_eval(self):
         expected = datetime(2016, 11, 7)
         self.assertEqual(result, expected)
 
+        result = datetime_eval("datetime('2018')")
+        expected = datetime(2018, 1, 1)
+        self.assertEqual(result, expected)
+
+        result = datetime_eval("datetime('2018-9')")
+        expected = datetime(2018, 9, 1)
+        self.assertEqual(result, expected)
+
         # Parse compact arguments spelling
         result = datetime_eval("dateadd(datetime('today'),1,year,)")
         expected = datetime(2017, 11, 7)