Fix typing of Timezone and ZoneInfo (#670)

Author: bryanforbes

pendulum/_extensions/helpers.py

@@ -353,7 +353,7 @@ def _get_tzinfo_name(tzinfo: datetime.tzinfo | None) -> str | None:
 
     if hasattr(tzinfo, "key"):
         # zoneinfo timezone
-        return cast(str, cast(zoneinfo.ZoneInfo, tzinfo).key)
+        return cast(zoneinfo.ZoneInfo, tzinfo).key
     elif hasattr(tzinfo, "name"):
         # Pendulum timezone
         return cast(Timezone, tzinfo).name

pendulum/formatting/formatter.py

@@ -448,7 +448,7 @@ def _check_parsed(
 
         if parsed["quarter"] is not None:
             if validated["year"] is not None:
-                dt = pendulum.datetime(validated["year"], 1, 1)
+                dt = pendulum.datetime(cast(int, validated["year"]), 1, 1)
             else:
                 dt = now
 
@@ -476,8 +476,8 @@ def _check_parsed(
         if parsed["day_of_week"] is not None:
             dt = pendulum.datetime(
                 cast(int, validated["year"]),
-                validated["month"] or now.month,
-                validated["day"] or now.day,
+                cast(int, validated["month"]) or now.month,
+                cast(int, validated["day"]) or now.day,
             )
             dt = dt.start_of("week").subtract(days=1)
             dt = dt.next(parsed["day_of_week"])
@@ -502,9 +502,9 @@ def _check_parsed(
                 raise ValueError("Invalid date")
 
             pm = parsed["meridiem"] == "pm"
-            validated["hour"] %= 12
+            validated["hour"] %= 12  # type: ignore
             if pm:
-                validated["hour"] += 12
+                validated["hour"] += 12  # type: ignore
 
         if validated["month"] is None:
             if parsed["year"] is not None:

pendulum/parsing/iso8601.py

@@ -17,6 +17,7 @@
 from pendulum.parsing.exceptions import ParserError
 from pendulum.tz.timezone import UTC
 from pendulum.tz.timezone import FixedTimezone
+from pendulum.tz.timezone import Timezone
 
 ISO8601_DT = re.compile(
     # Date (optional)  # noqa: E800
@@ -107,7 +108,7 @@ def parse_iso8601(
     minute = 0
     second = 0
     microsecond = 0
-    tzinfo: FixedTimezone | None = None
+    tzinfo: FixedTimezone | Timezone | None = None
 
     if m.group("date"):
         # A date has been specified

pendulum/tz/local_timezone.py

@@ -239,7 +239,7 @@ def _get_unix_timezone(_root: str = "/") -> Timezone:
             continue
 
         with open(tzpath, "rb") as f:
-            return cast(Timezone, Timezone.from_file(f))
+            return Timezone.from_file(f)
 
     raise RuntimeError("Unable to find any timezone configuration")
 
@@ -251,7 +251,7 @@ def _tz_from_env(tzenv: str) -> Timezone:
     # TZ specifies a file
     if os.path.isfile(tzenv):
         with open(tzenv, "rb") as f:
-            return cast(Timezone, Timezone.from_file(f))
+            return Timezone.from_file(f)
 
     # TZ specifies a zoneinfo zone.
     try:

pendulum/tz/timezone.py

@@ -42,7 +42,7 @@ def datetime(
         raise NotImplementedError
 
 
-class Timezone(zoneinfo.ZoneInfo, PendulumTimezone):  # type: ignore[misc]
+class Timezone(zoneinfo.ZoneInfo, PendulumTimezone):
     """
     Represents a named timezone.
 
@@ -54,13 +54,13 @@ class Timezone(zoneinfo.ZoneInfo, PendulumTimezone):  # type: ignore[misc]
 
     def __new__(cls, key: str) -> Timezone:
         try:
-            return cast(Timezone, super().__new__(cls, key))
+            return super().__new__(cls, key)  # type: ignore[call-arg]
         except zoneinfo.ZoneInfoNotFoundError:
             raise InvalidTimezone(key)
 
     @property
     def name(self) -> str:
-        return cast(str, self.key)
+        return self.key
 
     def convert(
         self, dt: datetime_.datetime, raise_on_unknown_times: bool = False
@@ -86,11 +86,24 @@ def convert(
         '2013-03-30T21:30:00-04:00'
         """
         if dt.tzinfo is None:
-            offset_before = (
-                self.utcoffset(dt.replace(fold=0)) if dt.fold else self.utcoffset(dt)
+            # Technically, utcoffset() can return None, but none of the zone information
+            # in tzdata sets _tti_before to None. This can be checked with the following
+            # code:
+            #
+            # >>> import zoneinfo
+            # >>> from zoneinfo._zoneinfo import ZoneInfo
+            #
+            # >>> for tzname in zoneinfo.available_timezones():
+            # >>>     if ZoneInfo(tzname)._tti_before is None:
+            # >>>         print(tzname)
+
+            offset_before = cast(
+                datetime_.timedelta,
+                (self.utcoffset(dt.replace(fold=0)) if dt.fold else self.utcoffset(dt)),
             )
-            offset_after = (
-                self.utcoffset(dt) if dt.fold else self.utcoffset(dt.replace(fold=1))
+            offset_after = cast(
+                datetime_.timedelta,
+                (self.utcoffset(dt) if dt.fold else self.utcoffset(dt.replace(fold=1))),
             )
 
             if offset_after > offset_before:

pendulum/utils/_compat.py

@@ -5,9 +5,9 @@
 PYPY = hasattr(sys, "pypy_version_info")
 PY38 = sys.version_info[:2] >= (3, 8)
 
-try:
+if sys.version_info < (3, 9):
     from backports import zoneinfo
-except ImportError:
-    import zoneinfo  # type: ignore[no-redef]
+else:
+    import zoneinfo
 
 __all__ = ["zoneinfo"]