Be stricter on month=0

This relates #6

Author: kiorky

docs/CHANGES.rst

@@ -1,11 +1,11 @@
 Changelog
 ==============
 
-1.0.16 (unreleased)
+1.1.0 (unreleased)
 -------------------
 
-- Nothing changed yet.
-
+- Enforce validation for month=1. Before this release we used to support month=0 and it was silently glided to month=1 to support having both day in month in 4th field when it came to have 6fields cron forms (second repeat). It will now raises a CroniterBadDateError. See https://github.com/kiorky/croniter/issues/6
+  [kiorky]
 
 1.0.15 (2021-06-25)
 -------------------

src/croniter/croniter.py

@@ -712,7 +712,13 @@ def _expand(cls, expr_format, hash_id=None):
                     except ValueError:
                         pass
 
-                    if t in cls.LOWMAP[i]:
+                    if t in cls.LOWMAP[i] and not (
+                        # do not support 0 as a month either for classical 5 fields cron
+                        # or 6fields second repeat form
+                        # but still let conversion happen if day field is shifted
+                        (i == 3 and len(expressions) == 5) or
+                        (i == 4 and len(expressions) == 6)
+                    ):
                         t = cls.LOWMAP[i][t]
 
                     if (

src/croniter/tests/test_croniter.py

@@ -317,14 +317,14 @@ def testOptimizeCronExpressions(self):
         wildcard = ['*']
         m, h, d, mon, dow, s = range(6)
         # Test each field individually
-        self.assertEqual(croniter('0-59 0 0 0 0').expanded[m], wildcard)
-        self.assertEqual(croniter('0 0-23 0 0 0').expanded[h], wildcard)
-        self.assertEqual(croniter('0 0 0-31 0 0').expanded[d], wildcard)
+        self.assertEqual(croniter('0-59 0 0 1 0').expanded[m], wildcard)
+        self.assertEqual(croniter('0 0-23 0 1 0').expanded[h], wildcard)
+        self.assertEqual(croniter('0 0 0-31 1 0').expanded[d], wildcard)
         self.assertEqual(croniter('0 0 0 1-12 0').expanded[mon], wildcard)
-        self.assertEqual(croniter('0 0 0 0 0-6').expanded[dow], wildcard)
-        self.assertEqual(croniter('0 0 0 0 1-7').expanded[dow], wildcard)
-        self.assertEqual(croniter('0 0 0 0 1-7,sat#3').expanded[dow], wildcard)
-        self.assertEqual(croniter('0 0 0 0 0 0-59').expanded[s], wildcard)
+        self.assertEqual(croniter('0 0 0 1 0-6').expanded[dow], wildcard)
+        self.assertEqual(croniter('0 0 0 1 1-7').expanded[dow], wildcard)
+        self.assertEqual(croniter('0 0 0 1 1-7,sat#3').expanded[dow], wildcard)
+        self.assertEqual(croniter('0 0 0 1 0 0-59').expanded[s], wildcard)
         # Real life examples
         self.assertEqual(croniter('30 1-12,0,10-23 15-21 * fri').expanded[h], wildcard)
         self.assertEqual(croniter('30 1-23,0 15-21 * fri').expanded[h], wildcard)
@@ -993,12 +993,12 @@ def test_issue_monsun_117(self):
              '2019-01-17 00:00:01',
              '2019-01-18 00:00:02',
              '2019-01-19 00:00:03',
-             '2019-01-20 00:00:04',
              '2019-01-23 00:00:00',
              '2019-01-24 00:00:01',
              '2019-01-25 00:00:02',
              '2019-01-26 00:00:03',
-             '2019-01-27 00:00:04'])
+             '2019-01-30 00:00:00',
+             '2019-01-31 00:00:01'])
 
     def test_mixdow(self):
         base = datetime(2018, 10, 1, 0, 0)
@@ -1433,11 +1433,14 @@ def test_issue156(self):
 
     def test_confirm_sort(self):
         m, h, d, mon, dow, s = range(6)
-        self.assertListEqual(croniter('0 8,22,10,23 0 0 0').expanded[h], [8, 10, 22, 23])
-        self.assertListEqual(croniter('0 0 25-L 0 0').expanded[d], [25, 26, 27, 28, 29, 30, 31])
+        self.assertListEqual(croniter('0 8,22,10,23 0 1 0').expanded[h], [8, 10, 22, 23])
+        self.assertListEqual(croniter('0 0 25-L 1 0').expanded[d], [25, 26, 27, 28, 29, 30, 31])
         self.assertListEqual(croniter("1 1 7,14,21,L * *").expanded[d], [7, 14, 21, "l"])
         self.assertListEqual(croniter("0 0 * * *,sat#3").expanded[dow], ["*", 6])
 
+    def test_issue_k6(self):
+        self.assertRaises(CroniterBadCronError, croniter, '0 0 0 0 0')
+
 
 if __name__ == '__main__':
     unittest.main()