Fixes wrong result when adding/subtracting a Period if a DST transition occurs.

Fixes #125

Author: sdispater

CHANGELOG.md

@@ -1,5 +1,13 @@
 # Change Log
 
+## [Unreleased]
+
+### Fixed
+
+- Fixed `next()` and `previous()` hanging when passed an invalid input.
+- Fixed wrong result when adding/subtracting a Period if a DST transition occurs.
+
+
 ## [1.2.1] - 2017-05-23
 
 ### Fixed

pendulum/pendulum.py

@@ -1140,6 +1140,14 @@ def add_timedelta(self, delta):
 
         :rtype: Pendulum
         """
+        if isinstance(delta, Period):
+            return self.add(
+                years=delta.years, months=delta.months,
+                weeks=delta.weeks, days=delta.remaining_days,
+                hours=delta.hours, minutes=delta.minutes,
+                seconds=delta.remaining_seconds, microseconds=delta.microseconds
+            )
+
         return self.add(days=delta.days, seconds=delta.seconds,
                         microseconds=delta.microseconds)
 
@@ -1152,6 +1160,14 @@ def subtract_timedelta(self, delta):
 
         :rtype: Pendulum
         """
+        if isinstance(delta, Period):
+            return self.subtract(
+                years=delta.years, months=delta.months,
+                weeks=delta.weeks, days=delta.remaining_days,
+                hours=delta.hours, minutes=delta.minutes,
+                seconds=delta.remaining_seconds, microseconds=delta.microseconds
+            )
+
         return self.subtract(days=delta.days, seconds=delta.seconds,
                              microseconds=delta.microseconds)
 

tests/period_tests/test_add_subtract.py

@@ -0,0 +1,21 @@
+# -*- coding: utf-8 -*-
+
+import pendulum
+
+
+def test_dst_add():
+    start = pendulum.create(2017, 3, 7, tz='America/Toronto')
+    end = start.add(days=6)
+    period = end - start
+    new_end = start + period
+
+    assert new_end == end
+
+
+def test_dst_subtract():
+    start = pendulum.create(2017, 3, 7, tz='America/Toronto')
+    end = start.add(days=6)
+    period = end - start
+    new_start = end - period
+
+    assert new_start == start

tests/period_tests/test_construct.py

@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 
+import pendulum
 from datetime import datetime
 from pendulum import Period, Pendulum
 
@@ -72,6 +73,18 @@ def test_accuracy(self):
         self.assertEqual(4, p2.remaining_days)
         self.assertEqual(5824, p2.in_days())
 
+    def test_dst_transition(self):
+        start = pendulum.create(2017, 3, 7, tz='America/Toronto')
+        end = start.add(days=6)
+        period = end - start
+
+        assert period.days == 5
+        assert period.seconds == 82800
+
+        assert period.remaining_days == 6
+        assert period.hours == 0
+        assert period.remaining_seconds == 0
+
     def test_timedelta_behavior(self):
         dt1 = Pendulum(2000, 11, 20, 1)
         dt2 = Pendulum(2000, 11, 25, 2)