Update the CheckInfraFreeze canned check to use datetime & zoneinfo.

The current implementation of CheckInfraFreeze relies on timestamps
being preconverted to UNIX timestamps because zoneinfo doesn't work by
default on Windows. The necessary tzdata package has been added so that
zoneinfo will work for Windows, so switching to datetime and zoneinfo is
now possible and makes it easier to update the time range for freezes.

Bug: 1521396
Change-Id: I8db111f05db2e79f4fffd9da3829b9071d12163f
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/tools/depot_tools/+/5246425
Commit-Queue: Garrett Beaty <gbeaty@google.com>
Reviewed-by: Gavin Mak <gavinmak@google.com>

.vpython3

@@ -52,6 +52,13 @@ wheel: <
   version: "version:1.0.9"
 >
 
+# Used by:
+#    presubmit_canned_checks.py (via zoneinfo)
+wheel: <
+  name: "infra/python/wheels/tzdata-py2_py3"
+  version: "version:2023.4"
+>
+
 # Used by:
 #   my_activity.py
 wheel: <

presubmit_canned_checks.py

@@ -3,9 +3,11 @@
 # found in the LICENSE file.
 """Generic presubmit checks that can be reused by other presubmit checks."""
 
+import datetime
 import io as _io
 import os as _os
 import time
+import zoneinfo
 
 import metadata.discover
 import metadata.validate
@@ -890,14 +892,9 @@ def CheckChromiumDependencyMetadata(input_api, output_api, file_filter=None):
 
 _IGNORE_FREEZE_FOOTER = 'Ignore-Freeze'
 
-# The time module's handling of timezones is abysmal, so the boundaries are
-# precomputed in UNIX time
-# TODO: crbug.com/1521396 - Specify the timestamps using datetime and zoneinfo
-# once the tzdata package is available as a dependency for Windows (Windows
-# doesn't have a timezone database by default, so zoneinfo doesn't work)
-_FREEZE_START = 1702627200  # 2023/12/15 00:00 -0800
-_FREEZE_END = 1704182400  # 2024/01/02 00:00 -0800
-
+_FREEZE_TZ = zoneinfo.ZoneInfo("America/Los_Angeles")
+_FREEZE_START = datetime.datetime(2023, 12, 15, 0, 0, tzinfo=_FREEZE_TZ)
+_FREEZE_END = datetime.datetime(2024, 1, 2, 0, 0, tzinfo=_FREEZE_TZ)
 
 def CheckInfraFreeze(input_api,
                      output_api,
@@ -923,7 +920,7 @@ def CheckInfraFreeze(input_api,
             will be excluded.
     """
     # Not in the freeze time range
-    now = input_api.time.time()
+    now = datetime.datetime.now(_FREEZE_TZ)
     if now < _FREEZE_START or now >= _FREEZE_END:
         input_api.logging.info('No freeze is in effect')
         return []
@@ -951,12 +948,6 @@ def CheckInfraFreeze(input_api,
         input_api.logging.info('No affected files are covered by freeze')
         return []
 
-    # TODO: crbug.com/1521396 - When _FREEZE_START and _FREEZE_END are datetime
-    # objects, they can be printed directly and this function can be removed
-    def convert(t):
-        ts = input_api.time.localtime(t)
-        return input_api.time.strftime('%Y/%m/%d %H:%M %z', ts)
-
     # Don't report errors when on the presubmit --all bot or when testing with
     # presubmit --files.
     if input_api.no_diffs:
@@ -966,8 +957,7 @@ def CheckInfraFreeze(input_api,
     return [
         report_type('There is a prod infra freeze in effect from {} until {},'
                     'the following files cannot be modified:\n  {}'.format(
-                        convert(_FREEZE_START), convert(_FREEZE_END),
-                        '\n  '.join(files)))
+                        _FREEZE_START, _FREEZE_END, '\n  '.join(files)))
     ]