libs.tz_utils: Add checks to validate_dt_tz

cl_sii/libs/tz_utils.py

@@ -166,5 +166,12 @@ def validate_dt_tz(value: datetime, tz: PytzTimezone) -> None:
     """
     if not dt_is_aware(value):
         raise ValueError("Value must be a timezone-aware datetime object.")
+
+    # The 'zone' attribute is not defined in the abstract base class 'datetime.tzinfo'. We need to
+    # check that it is there before using it below to prevent unexpected exceptions when dealing
+    # with Python Standard Library time zones that are instances of class 'datetime.timezone'.
+    assert hasattr(value.tzinfo, 'zone'), f"Object {value.tzinfo!r} must have 'zone' attribute."
+    assert hasattr(tz, 'zone'), f"Object {tz!r} must have 'zone' attribute."
+
     if value.tzinfo.zone != tz.zone:  # type: ignore
         raise ValueError(f"Timezone of datetime value must be '{tz.zone!s}'.", value)

tests/test_libs_tz_utils.py

@@ -1,9 +1,11 @@
+import datetime
+import re
 import unittest
 
 from cl_sii.libs.tz_utils import (  # noqa: F401
     convert_naive_dt_to_tz_aware, convert_tz_aware_dt_to_naive,
     dt_is_aware, dt_is_naive, get_now_tz_aware, validate_dt_tz,
-    PytzTimezone, TZ_UTC,
+    PytzTimezone, _TZ_CL_SANTIAGO, TZ_UTC,
 )
 
 
@@ -37,3 +39,46 @@ def test_dt_is_naive(self) -> None:
     def test_validate_dt_tz(self) -> None:
         # TODO: implement for 'validate_dt_tz'
         pass
+
+    def test_validate_dt_tz_tzinfo_zone_attribute_check(self) -> None:
+        # Time zone: UTC. Source: Pytz:
+        tzinfo_utc_pytz = TZ_UTC
+        dt_with_tzinfo_utc_pytz = convert_naive_dt_to_tz_aware(
+            datetime.datetime(2021, 1, 6, 15, 21),
+            tzinfo_utc_pytz,
+        )
+
+        # Time zone: UTC. Source: Python Standard Library:
+        tzinfo_utc_stdlib = datetime.timezone.utc
+        dt_with_tzinfo_utc_stdlib = datetime.datetime.fromisoformat('2021-01-06T15:04+00:00')
+
+        # Time zone: Not UTC. Source: Pytz:
+        tzinfo_not_utc_pytz = _TZ_CL_SANTIAGO
+        dt_with_tzinfo_not_utc_pytz = convert_naive_dt_to_tz_aware(
+            datetime.datetime(2021, 1, 6, 15, 21),
+            tzinfo_not_utc_pytz,
+        )
+
+        # Time zone: Not UTC. Source: Python Standard Library:
+        tzinfo_not_utc_stdlib = datetime.timezone(datetime.timedelta(days=-1, seconds=75600))
+        dt_with_tzinfo_not_utc_stdlib = datetime.datetime.fromisoformat('2021-01-06T15:04-03:00')
+
+        # Test datetimes with UTC time zone:
+        expected_error_message = re.compile(
+            r"^Object datetime.timezone.utc must have 'zone' attribute.$"
+        )
+        with self.assertRaisesRegex(AssertionError, expected_error_message):
+            validate_dt_tz(dt_with_tzinfo_utc_pytz, tzinfo_utc_stdlib)
+        with self.assertRaisesRegex(AssertionError, expected_error_message):
+            validate_dt_tz(dt_with_tzinfo_utc_stdlib, tzinfo_utc_pytz)
+
+        # Test datetimes with non-UTC time zone:
+        expected_error_message = re.compile(
+            r"^Object"
+            r" datetime.timezone\(datetime.timedelta\(days=-1, seconds=75600\)\)"
+            r" must have 'zone' attribute.$"
+        )
+        with self.assertRaisesRegex(AssertionError, expected_error_message):
+            validate_dt_tz(dt_with_tzinfo_not_utc_pytz, tzinfo_not_utc_stdlib)  # type: ignore
+        with self.assertRaisesRegex(AssertionError, expected_error_message):
+            validate_dt_tz(dt_with_tzinfo_not_utc_stdlib, tzinfo_not_utc_pytz)