refactor: accept tz name in timezone util methods and refactor iana-changes-updates script (ietf-tools#4444)

* refactor: accept tz name strings in ietf.utils.timezone methods

* refactor: use explicitly tz-aware math for iana-changes-updates script

* chore: remove unused "local_timezone_to_utc()" method helper

Author: jennifer-richards

ietf/bin/iana-changes-updates

@@ -18,6 +18,7 @@ django.setup()
 
 from django.conf import settings
 from optparse import OptionParser
+from zoneinfo import ZoneInfo
 
 parser = OptionParser()
 parser.add_option("-f", "--from", dest="start",
@@ -38,21 +39,30 @@ CLOCK_SKEW_COMPENSATION = 5 # seconds
 MAX_INTERVAL_ACCEPTED_BY_IANA = datetime.timedelta(hours=23)
 
 
+local_tzinfo = ZoneInfo(settings.TIME_ZONE)
 start = datetime.datetime.now() - datetime.timedelta(hours=23) + datetime.timedelta(seconds=CLOCK_SKEW_COMPENSATION)
 if options.start:
     start = datetime.datetime.strptime(options.start, "%Y-%m-%d %H:%M:%S")
+start = start.replace(tzinfo=local_tzinfo).astimezone(datetime.timezone.utc)
 
 end = start + datetime.timedelta(hours=23)
 if options.end:
-    end = datetime.datetime.strptime(options.end, "%Y-%m-%d %H:%M:%S")
+    end = datetime.datetime.strptime(options.end, "%Y-%m-%d %H:%M:%S").replace(tzinfo=local_tzinfo)
+end = end.astimezone(datetime.timezone.utc)
 
 syslog.openlog(os.path.basename(__file__), syslog.LOG_PID, syslog.LOG_USER)
 
 # ----------------------------------------------------------------------
 
 from ietf.sync.iana import fetch_changes_json, parse_changes_json, update_history_with_changes
 
-syslog.syslog("Updating history log with new changes from IANA from %s, period %s - %s" % (settings.IANA_SYNC_CHANGES_URL, start, end))
+syslog.syslog(
+    "Updating history log with new changes from IANA from %s, period %s - %s" % (
+        settings.IANA_SYNC_CHANGES_URL,
+        start.astimezone(local_tzinfo),
+        end.astimezone(local_tzinfo),
+    )
+)
 
 t = start
 while t < end:

ietf/sync/iana.py

@@ -24,7 +24,6 @@
 from ietf.person.models import Person
 from ietf.utils.log import log
 from ietf.utils.mail import parseaddr, get_payload_text
-from ietf.utils.timezone import local_timezone_to_utc
 
 
 #PROTOCOLS_URL = "https://www.iana.org/protocols/"
@@ -67,8 +66,8 @@ def update_rfc_log_from_protocol_page(rfc_names, rfc_must_published_later_than):
 
 
 def fetch_changes_json(url, start, end):
-    url += "?start=%s&end=%s" % (urlquote(local_timezone_to_utc(start).strftime("%Y-%m-%d %H:%M:%S")),
-                                 urlquote(local_timezone_to_utc(end).strftime("%Y-%m-%d %H:%M:%S")))
+    url += "?start=%s&end=%s" % (urlquote(start.astimezone(datetime.timezone.utc).strftime("%Y-%m-%d %H:%M:%S")),
+                                 urlquote(end.astimezone(datetime.timezone.utc).strftime("%Y-%m-%d %H:%M:%S")))
     # HTTP basic auth
     username = "ietfsync"
     password = settings.IANA_SYNC_PASSWORD

ietf/utils/timezone.py

@@ -1,6 +1,6 @@
-import pytz
 import datetime
 
+from typing import Union
 from zoneinfo import ZoneInfo
 
 from django.conf import settings
@@ -19,60 +19,58 @@
 RPC_TZINFO = ZoneInfo('PST8PDT')
 
 
-def make_aware(dt, tzinfo):
+def _tzinfo(tz: Union[str, datetime.tzinfo, None]):
+    """Helper to convert a tz param into a tzinfo
+
+    Accepts Defaults to UTC.
+    """
+    if tz is None:
+        return datetime.timezone.utc
+    elif isinstance(tz, datetime.tzinfo):
+        return tz
+    else:
+        return ZoneInfo(tz)
+
+
+def make_aware(dt, tz):
     """Assign timezone to a naive datetime
 
     Helper to deal with both pytz and zoneinfo type time zones. Can go away when pytz is removed.
     """
+    tzinfo = _tzinfo(tz)
     if hasattr(tzinfo, 'localize'):
         return tzinfo.localize(dt)  # pytz-style
     else:
         return dt.replace(tzinfo=tzinfo)  # zoneinfo- / datetime.timezone-style
 
 
-def local_timezone_to_utc(d):
-    """Takes a naive datetime in the local timezone and returns a
-    naive datetime with the corresponding UTC time."""
-    local_timezone = pytz.timezone(settings.TIME_ZONE)
-
-    d = local_timezone.localize(d).astimezone(pytz.utc)
-
-    return d.replace(tzinfo=None)
-
-
-def datetime_from_date(date, tz=pytz.utc):
+def datetime_from_date(date, tz=None):
     """Get datetime at midnight on a given date"""
     # accept either pytz or zoneinfo tzinfos until we get rid of pytz
-    return make_aware(datetime.datetime(date.year, date.month, date.day), tz)
+    return make_aware(datetime.datetime(date.year, date.month, date.day), _tzinfo(tz))
 
 
-def datetime_today(tzinfo=None):
+def datetime_today(tz=None):
     """Get a timezone-aware datetime representing midnight today
 
     For use with datetime fields representing a date.
     """
-    if tzinfo is None:
-        tzinfo = pytz.utc
-    return timezone.now().astimezone(tzinfo).replace(hour=0, minute=0, second=0, microsecond=0)
+    return timezone.now().astimezone(_tzinfo(tz)).replace(hour=0, minute=0, second=0, microsecond=0)
 
 
-def date_today(tzinfo=None):
+def date_today(tz=None):
     """Get the date corresponding to the current moment
 
     Note that Dates are not themselves timezone aware.
     """
-    if tzinfo is None:
-        tzinfo = pytz.utc
-    return timezone.now().astimezone(tzinfo).date()
+    return timezone.now().astimezone(_tzinfo(tz)).date()
 
 
-def time_now(tzinfo=None):
+def time_now(tz=None):
     """Get the "wall clock" time corresponding to the current moment
 
     The value returned by this data is a Time with no tzinfo attached. (Time
     objects have only limited timezone support, even if tzinfo is filled in,
     and may not behave correctly when daylight savings time shifts are relevant.)
     """
-    if tzinfo is None:
-        tzinfo = pytz.utc
-    return timezone.now().astimezone(tzinfo).time()
+    return timezone.now().astimezone(_tzinfo(tz)).time()