Bugfix for datetime objects with tzinfo from zoneinfo library

See https://github.com/collective/icalendar/issues/333 for details

Includes test code and changelog entry

CHANGES.rst

@@ -15,7 +15,10 @@ New features:
 
 Bug fixes:
 
-- *add item here*
+- proper handling of datetime objects with `tzinfo` generated through zoneinfo.ZoneInfo.
+  Ref: #334
+  Fixes: #333
+  [tobixen]
 
 
 4.0.9 (2021-10-16)

docs/credits.rst

@@ -56,6 +56,7 @@ icalendar contributors
 - Clive Stevens <clivest2@gmail.com>
 - Dalton Durst <github@daltondur.st>
 - Kamil Mańkowski <kam193@wp.pl>
+- Tobias Brox <tobias@redpill-linpro.com>
 
 Find out who contributed::
 

src/icalendar/parser.py

@@ -53,15 +53,14 @@ def tzid_from_dt(dt):
     tzid = None
     if hasattr(dt.tzinfo, 'zone'):
         tzid = dt.tzinfo.zone  # pytz implementation
+    elif hasattr(dt.tzinfo, 'key'):
+        tzid = dt.tzinfo.key # ZoneInfo implementation
     elif hasattr(dt.tzinfo, 'tzname'):
-        try:
+        # dateutil implementation, but this is broken
-            tzid = dt.tzinfo.tzname(dt)  # dateutil implementation
+        # See https://github.com/collective/icalendar/issues/333 for details
-        except AttributeError:
+        tzid = dt.tzinfo.tzname(dt)
-            # No tzid available
-            pass
     return tzid
 
-
 def foldline(line, limit=75, fold_sep='\r\n '):
     """Make a string folded as defined in RFC5545
     Lines of text SHOULD NOT be longer than 75 octets, excluding the line

src/icalendar/tests/test_timezoned.py

@@ -8,11 +8,50 @@ import dateutil.parser
 import icalendar
 import os
 import pytz
-
+try:
+    import zoneinfo
+except:
+    try:
+        from backports import zoneinfo
+    except:
+        zoneinfo = None
 
 class TestTimezoned(unittest.TestCase):
 
-    def test_create_from_ical(self):
+    def test_create_from_ical_zoneinfo(self):
+        directory = os.path.dirname(__file__)
+        with open(os.path.join(directory, 'timezoned.ics'), 'rb') as fp:
+            data = fp.read()
+        cal = icalendar.Calendar.from_ical(data)
+
+        self.assertEqual(
+            cal['prodid'].to_ical(),
+            b"-//Plone.org//NONSGML plone.app.event//EN"
+        )
+
+        timezones = cal.walk('VTIMEZONE')
+        self.assertEqual(len(timezones), 1)
+
+        tz = timezones[0]
+        self.assertEqual(tz['tzid'].to_ical(), b"Europe/Vienna")
+
+        std = tz.walk('STANDARD')[0]
+        self.assertEqual(
+            std.decoded('TZOFFSETFROM'),
+            datetime.timedelta(0, 7200)
+        )
+
+        ev1 = cal.walk('VEVENT')[0]
+        self.assertEqual(
+            ev1.decoded('DTSTART'),
+            datetime.datetime(2012, 2, 13, 10, 0, 0, tzinfo=zoneinfo.ZoneInfo('Europe/Vienna'))
+        )
+        self.assertEqual(
+            ev1.decoded('DTSTAMP'),
+            datetime.datetime(2010, 10, 10, 9, 10, 10, tzinfo=zoneinfo.ZoneInfo('UTC'))
+        )
+
+    def test_create_from_ical_pytz(self):
         directory = os.path.dirname(__file__)
         with open(os.path.join(directory, 'timezoned.ics'), 'rb') as fp:
             data = fp.read()
@@ -49,7 +88,7 @@ class TestTimezoned(unittest.TestCase):
             )
         )
 
-    def test_create_to_ical(self):
+    def test_create_to_ical_pytz(self):
         cal = icalendar.Calendar()
 
         cal.add('prodid', "-//Plone.org//NONSGML plone.app.event//EN")
@@ -132,6 +171,90 @@ class TestTimezoned(unittest.TestCase):
         self.assertTrue("DTSTAMP;VALUE=DATE-TIME:20101010T081010Z" in test_out)
         self.assertTrue("CREATED;VALUE=DATE-TIME:20101010T081010Z" in test_out)
 
+    def test_create_to_ical_zoneinfo(self):
+        cal = icalendar.Calendar()
+
+        cal.add('prodid', "-//Plone.org//NONSGML plone.app.event//EN")
+        cal.add('version', "2.0")
+        cal.add('x-wr-calname', "test create calendar")
+        cal.add('x-wr-caldesc', "icalendar tests")
+        cal.add('x-wr-relcalid', "12345")
+        cal.add('x-wr-timezone', "Europe/Vienna")
+
+        tzc = icalendar.Timezone()
+        tzc.add('tzid', 'Europe/Vienna')
+        tzc.add('x-lic-location', 'Europe/Vienna')
+
+        tzs = icalendar.TimezoneStandard()
+        tzs.add('tzname', 'CET')
+        tzs.add('dtstart', datetime.datetime(1970, 10, 25, 3, 0, 0))
+        tzs.add('rrule', {'freq': 'yearly', 'bymonth': 10, 'byday': '-1su'})
+        tzs.add('TZOFFSETFROM', datetime.timedelta(hours=2))
+        tzs.add('TZOFFSETTO', datetime.timedelta(hours=1))
+
+        tzd = icalendar.TimezoneDaylight()
+        tzd.add('tzname', 'CEST')
+        tzd.add('dtstart', datetime.datetime(1970, 3, 29, 2, 0, 0))
+        tzs.add('rrule', {'freq': 'yearly', 'bymonth': 3, 'byday': '-1su'})
+        tzd.add('TZOFFSETFROM', datetime.timedelta(hours=1))
+        tzd.add('TZOFFSETTO', datetime.timedelta(hours=2))
+
+        tzc.add_component(tzs)
+        tzc.add_component(tzd)
+        cal.add_component(tzc)
+
+        event = icalendar.Event()
+        tz = zoneinfo.ZoneInfo("Europe/Vienna")
+        event.add(
+            'dtstart',
+            datetime.datetime(2012, 2, 13, 10, 00, 00, tzinfo=tz))
+        event.add(
+            'dtend',
+            datetime.datetime(2012, 2, 17, 18, 00, 00, tzinfo=tz))
+        event.add(
+            'dtstamp',
+            datetime.datetime(2010, 10, 10, 10, 10, 10, tzinfo=tz))
+        event.add(
+            'created',
+            datetime.datetime(2010, 10, 10, 10, 10, 10, tzinfo=tz))
+        event.add('uid', '123456')
+        event.add(
+            'last-modified',
+            datetime.datetime(2010, 10, 10, 10, 10, 10, tzinfo=tz))
+        event.add('summary', 'artsprint 2012')
+        # event.add('rrule', 'FREQ=YEARLY;INTERVAL=1;COUNT=10')
+        event.add('description', 'sprinting at the artsprint')
+        event.add('location', 'aka bild, wien')
+        event.add('categories', 'first subject')
+        event.add('categories', 'second subject')
+        event.add('attendee', 'häns')
+        event.add('attendee', 'franz')
+        event.add('attendee', 'sepp')
+        event.add('contact', 'Max Mustermann, 1010 Wien')
+        event.add('url', 'http://plone.org')
+        cal.add_component(event)
+
+        test_out = b'|'.join(cal.to_ical().splitlines())
+        test_out = test_out.decode('utf-8')
+
+        vtimezone_lines = "BEGIN:VTIMEZONE|TZID:Europe/Vienna|X-LIC-LOCATION:"
+        "Europe/Vienna|BEGIN:STANDARD|DTSTART;VALUE=DATE-TIME:19701025T03"
+        "0000|RRULE:FREQ=YEARLY;BYDAY=-1SU;BYMONTH=10|RRULE:FREQ=YEARLY;B"
+        "YDAY=-1SU;BYMONTH=3|TZNAME:CET|TZOFFSETFROM:+0200|TZOFFSETTO:+01"
+        "00|END:STANDARD|BEGIN:DAYLIGHT|DTSTART;VALUE=DATE-TIME:19700329T"
+        "020000|TZNAME:CEST|TZOFFSETFROM:+0100|TZOFFSETTO:+0200|END:DAYLI"
+        "GHT|END:VTIMEZONE"
+        self.assertTrue(vtimezone_lines in test_out)
+
+        test_str = "DTSTART;TZID=Europe/Vienna;VALUE=DATE-TIME:20120213T100000"
+        self.assertTrue(test_str in test_out)
+        self.assertTrue("ATTENDEE:sepp" in test_out)
+
+        # ical standard expects DTSTAMP and CREATED in UTC
+        self.assertTrue("DTSTAMP;VALUE=DATE-TIME:20101010T081010Z" in test_out)
+        self.assertTrue("CREATED;VALUE=DATE-TIME:20101010T081010Z" in test_out)
+
+
     def test_tzinfo_dateutil(self):
         # Test for issues #77, #63
         # references: #73,7430b66862346fe3a6a100ab25e35a8711446717