Extend pre-compiled Duration and Timestamp instead of manual definition

betterproto/__init__.py

@@ -941,19 +941,10 @@ def which_one_of(message: Message, group_name: str) -> Tuple[str, Any]:
     return (field_name, getattr(message, field_name))
 
 
-@dataclasses.dataclass
+from .lib.google.protobuf import Duration, Timestamp
-class _Duration(Message):
-    # Signed seconds of the span of time. Must be from -315,576,000,000 to
-    # +315,576,000,000 inclusive. Note: these bounds are computed from: 60
-    # sec/min * 60 min/hr * 24 hr/day * 365.25 days/year * 10000 years
-    seconds: int = int64_field(1)
-    # Signed fractions of a second at nanosecond resolution of the span of time.
-    # Durations less than one second are represented with a 0 `seconds` field and
-    # a positive or negative `nanos` field. For durations of one second or more,
-    # a non-zero value for the `nanos` field must be of the same sign as the
-    # `seconds` field. Must be from -999,999,999 to +999,999,999 inclusive.
-    nanos: int = int32_field(2)
 
+
+class _Duration(Duration):
     def to_timedelta(self) -> timedelta:
         return timedelta(seconds=self.seconds, microseconds=self.nanos / 1e3)
 
@@ -966,16 +957,7 @@ class _Duration(Message):
         return ".".join(parts) + "s"
 
 
-@dataclasses.dataclass
+class _Timestamp(Timestamp):
-class _Timestamp(Message):
-    # Represents seconds of UTC time since Unix epoch 1970-01-01T00:00:00Z. Must
-    # be from 0001-01-01T00:00:00Z to 9999-12-31T23:59:59Z inclusive.
-    seconds: int = int64_field(1)
-    # Non-negative fractions of a second at nanosecond resolution. Negative
-    # second values with fractions must still have non-negative nanos values that
-    # count forward in time. Must be from 0 to 999,999,999 inclusive.
-    nanos: int = int32_field(2)
-
     def to_datetime(self) -> datetime:
         ts = self.seconds + (self.nanos / 1e9)
         return datetime.fromtimestamp(ts, tz=timezone.utc)