From 42c51019571b9a0de662b9eaebd1fd01b769b771 Mon Sep 17 00:00:00 2001
From: Ruben Laguna <ruben.laguna@gmail.com>
Date: Wed, 23 Jun 2021 16:31:45 +0200
Subject: [PATCH] Fix ``AttributeError``: ``datetime.timezone`` object has no
 attribute ``name`` (#16599)

closes: #16551

Previous implementation tried to force / coerce the provided timezone (from the dag's `start_date`) into a `pendulum.tz.timezone.*` that only worked if the provided timezone was already a pendulum's timezone and it specifically failed when with `datetime.timezone.utc` as timezone.

(cherry picked from commit 86c20910aed48f7d5b2ebaa91fa40d47c52d7db3)
---
 airflow/models/dag.py                         |  4 +-
 tests/models/test_dag.py                      | 40 +++++++++++++++++++
 tests/serialization/test_dag_serialization.py |  2 +
 3 files changed, 44 insertions(+), 2 deletions(-)

diff --git a/airflow/models/dag.py b/airflow/models/dag.py
index 1861edaff193b..13d69c28071eb 100644
--- a/airflow/models/dag.py
+++ b/airflow/models/dag.py
@@ -485,7 +485,7 @@ def following_schedule(self, dttm):
             else:
                 # absolute (e.g. 3 AM)
                 naive = cron.get_next(datetime)
-                tz = pendulum.timezone(self.timezone.name)
+                tz = self.timezone
                 following = timezone.make_aware(naive, tz)
             return timezone.convert_to_utc(following)
         elif self.normalized_schedule_interval is not None:
@@ -513,7 +513,7 @@ def previous_schedule(self, dttm):
             else:
                 # absolute (e.g. 3 AM)
                 naive = cron.get_prev(datetime)
-                tz = pendulum.timezone(self.timezone.name)
+                tz = self.timezone
                 previous = timezone.make_aware(naive, tz)
             return timezone.convert_to_utc(previous)
         elif self.normalized_schedule_interval is not None:
diff --git a/tests/models/test_dag.py b/tests/models/test_dag.py
index 939baf4931cc6..34d761d4eb410 100644
--- a/tests/models/test_dag.py
+++ b/tests/models/test_dag.py
@@ -621,6 +621,46 @@ def test_following_schedule_relativedelta(self):
         _next = dag.following_schedule(_next)
         assert _next.isoformat() == "2015-01-02T02:00:00+00:00"
 
+    def test_previous_schedule_datetime_timezone(self):
+        # Check that we don't get an AttributeError 'name' for self.timezone
+
+        start = datetime.datetime(2018, 3, 25, 2, tzinfo=datetime.timezone.utc)
+        dag = DAG('tz_dag', start_date=start, schedule_interval='@hourly')
+        when = dag.previous_schedule(start)
+        assert when.isoformat() == "2018-03-25T01:00:00+00:00"
+
+    def test_following_schedule_datetime_timezone(self):
+        # Check that we don't get an AttributeError 'name' for self.timezone
+
+        start = datetime.datetime(2018, 3, 25, 2, tzinfo=datetime.timezone.utc)
+        dag = DAG('tz_dag', start_date=start, schedule_interval='@hourly')
+        when = dag.following_schedule(start)
+        assert when.isoformat() == "2018-03-25T03:00:00+00:00"
+
+    def test_following_schedule_datetime_timezone_utc0530(self):
+        # Check that we don't get an AttributeError 'name' for self.timezone
+        class UTC0530(datetime.tzinfo):
+            """tzinfo derived concrete class named "+0530" with offset of 19800"""
+
+            # can be configured here
+            _offset = datetime.timedelta(seconds=19800)
+            _dst = datetime.timedelta(0)
+            _name = "+0530"
+
+            def utcoffset(self, dt):
+                return self.__class__._offset
+
+            def dst(self, dt):
+                return self.__class__._dst
+
+            def tzname(self, dt):
+                return self.__class__._name
+
+        start = datetime.datetime(2018, 3, 25, 10, tzinfo=UTC0530())
+        dag = DAG('tz_dag', start_date=start, schedule_interval='@hourly')
+        when = dag.following_schedule(start)
+        assert when.isoformat() == "2018-03-25T05:30:00+00:00"
+
     def test_dagtag_repr(self):
         clear_db_dags()
         dag = DAG('dag-test-dagtag', start_date=DEFAULT_DATE, tags=['tag-1', 'tag-2'])
diff --git a/tests/serialization/test_dag_serialization.py b/tests/serialization/test_dag_serialization.py
index f24e862cadca2..29e6ac00b0e45 100644
--- a/tests/serialization/test_dag_serialization.py
+++ b/tests/serialization/test_dag_serialization.py
@@ -27,6 +27,7 @@
 from glob import glob
 from unittest import mock
 
+import pendulum
 import pytest
 from dateutil.relativedelta import FR, relativedelta
 from kubernetes.client import models as k8s
@@ -444,6 +445,7 @@ def validate_deserialized_task(
                 datetime(2019, 7, 30, tzinfo=timezone.utc),
                 datetime(2019, 8, 1, tzinfo=timezone.utc),
             ),
+            (pendulum.datetime(2019, 8, 1, tz='UTC'), None, pendulum.datetime(2019, 8, 1, tz='UTC')),
         ]
     )
     def test_deserialization_start_date(self, dag_start_date, task_start_date, expected_task_start_date):