def coerce_naive_until(cls, rrule):
#
# RFC5545 specifies that the UNTIL rule part MUST ALWAYS be a date
# with UTC time. This is extra work for API implementers because
# it requires them to perform DTSTART local -> UTC datetime coercion on
# POST and UTC -> DTSTART local coercion on GET.
#
# This block of code is a departure from the RFC. If you send an
# rrule like this to the API (without a Z on the UNTIL):
#
# DTSTART;TZID=America/New_York:20180502T150000 RRULE:FREQ=HOURLY;INTERVAL=1;UNTIL=20180502T180000
#
# ...we'll assume that the naive UNTIL is intended to match the DTSTART
# timezone (America/New_York), and so we'll coerce to UTC _for you_
# automatically.
#
if 'until=' in rrule.lower():
# if DTSTART;TZID= is used, coerce "naive" UNTIL values
# to the proper UTC date
match_until = re.match(
r".*?(?P<until>UNTIL\=[0-9]+T[0-9]+)(?P<utcflag>Z?)", rrule)
if not len(match_until.group('utcflag')):
# rrule = DTSTART;TZID=America/New_York:20200601T120000 RRULE:...;UNTIL=20200601T170000
# Find the UNTIL=N part of the string
# naive_until = UNTIL=20200601T170000
naive_until = match_until.group('until')
# What is the DTSTART timezone for:
# DTSTART;TZID=America/New_York:20200601T120000 RRULE:...;UNTIL=20200601T170000Z
# local_tz = tzfile('/usr/share/zoneinfo/America/New_York')
local_tz = dateutil.rrule.rrulestr(
rrule.replace(naive_until, naive_until + 'Z'),
tzinfos=UTC_TIMEZONES)._dtstart.tzinfo
# Make a datetime object with tzinfo=<the DTSTART timezone>
# localized_until = datetime.datetime(2020, 6, 1, 17, 0, tzinfo=tzfile('/usr/share/zoneinfo/America/New_York'))
localized_until = make_aware(
datetime.datetime.strptime(
re.sub('^UNTIL=', '', naive_until), "%Y%m%dT%H%M%S"),
local_tz)
# Coerce the datetime to UTC and format it as a string w/ Zulu format
# utc_until = UNTIL=20200601T220000Z
utc_until = 'UNTIL=' + localized_until.astimezone(
pytz.utc).strftime('%Y%m%dT%H%M%SZ')
# rrule was: DTSTART;TZID=America/New_York:20200601T120000 RRULE:...;UNTIL=20200601T170000
# rrule is now: DTSTART;TZID=America/New_York:20200601T120000 RRULE:...;UNTIL=20200601T220000Z
rrule = rrule.replace(naive_until, utc_until)
return rrule
def rrulestr(cls, rrule, **kwargs):
"""
Apply our own custom rrule parsing logic. This applies some extensions
and limitations to parsing that are specific to our supported
implementation. Namely:
* python-dateutil doesn't _natively_ support `DTSTART;TZID=`; this
function parses out the TZID= component and uses it to produce the
`tzinfos` keyword argument to `dateutil.rrule.rrulestr()`. In this
way, we translate:
DTSTART;TZID=America/New_York:20180601T120000 RRULE:FREQ=DAILY;INTERVAL=1
...into...
DTSTART:20180601T120000TZID RRULE:FREQ=DAILY;INTERVAL=1
...and we pass a hint about the local timezone to dateutil's parser:
`dateutil.rrule.rrulestr(rrule, {
'tzinfos': {
'TZID': dateutil.tz.gettz('America/New_York')
}
})`
it's possible that we can remove the custom code that performs this
parsing if TZID= gains support in upstream dateutil:
https://github.com/dateutil/dateutil/pull/615
* RFC5545 specifies that: if the "DTSTART" property is specified as
a date with local time (in our case, TZID=), then the UNTIL rule part
MUST also be treated as a date with local time. If the "DTSTART"
property is specified as a date with UTC time (with a Z suffix),
then the UNTIL rule part MUST be specified as a date with UTC time.
this function provides additional parsing to translate RRULES like this:
DTSTART;TZID=America/New_York:20180601T120000 RRULE:FREQ=DAILY;INTERVAL=1;UNTIL=20180602T170000
...into this (under the hood):
DTSTART;TZID=America/New_York:20180601T120000 RRULE:FREQ=DAILY;INTERVAL=1;UNTIL=20180602T210000Z
"""
source_rrule = rrule
kwargs['tzinfos'] = {}
match = cls.TZID_REGEX.match(rrule)
if match is not None:
rrule = cls.TZID_REGEX.sub("DTSTART\g<stamp>TZI\g<rrule>", rrule)
timezone = gettz(match.group('tzid'))
if 'until' in rrule.lower():
# if DTSTART;TZID= is used, coerce "naive" UNTIL values
# to the proper UTC date
match_until = re.match(
".*?(?P<until>UNTIL\=[0-9]+T[0-9]+)(?P<utcflag>Z?)", rrule)
until_date = match_until.group('until').split("=")[1]
if len(match_until.group('utcflag')):
raise ValueError(
six.text_type(
_('invalid rrule `{}` includes TZINFO= stanza and UTC-based UNTIL clause'
).format(source_rrule))) # noqa
localized = make_aware(
datetime.datetime.strptime(until_date, "%Y%m%dT%H%M%S"),
timezone)
utc = localized.astimezone(pytz.utc).strftime('%Y%m%dT%H%M%SZ')
rrule = rrule.replace(match_until.group('until'),
'UNTIL={}'.format(utc))
kwargs['tzinfos']['TZI'] = timezone
x = dateutil.rrule.rrulestr(rrule, **kwargs)
return x