fix hightime accuracy and add femtosecond test

Author: lau-yeexuan

generated/nidaqmx/_time.py

@@ -22,8 +22,19 @@ def _convert_to_desired_timezone(
     # use ZoneInfo here to account for daylight savings
     if isinstance(tzinfo, ZoneInfo):
         localized_time = expected_time_utc.replace(tzinfo=tzinfo)
-        desired_expected_time = tzinfo.fromutc(localized_time)
-        return desired_expected_time  # type: ignore[return-value]  # https://github.com/ni/nidaqmx-python/issues/860
+        std_datetime_result = tzinfo.fromutc(localized_time)
+        desired_expected_time = ht_datetime(
+            std_datetime_result.year,
+            std_datetime_result.month,
+            std_datetime_result.day,
+            std_datetime_result.hour,
+            std_datetime_result.minute,
+            std_datetime_result.second,
+            std_datetime_result.microsecond,
+            std_datetime_result.femtosecond,
+            tzinfo=std_datetime_result.tzinfo
+        )
+        return desired_expected_time  
 
     # if the tzinfo passed in is a timedelta function, then we don't need to consider daylight savings  # noqa: W505 - doc line too long (102 > 100 characters) (auto-generated noqa)
     elif tzinfo.utcoffset(None) is not None:

src/handwritten/_time.py

@@ -22,8 +22,19 @@ def _convert_to_desired_timezone(
     # use ZoneInfo here to account for daylight savings
     if isinstance(tzinfo, ZoneInfo):
         localized_time = expected_time_utc.replace(tzinfo=tzinfo)
-        desired_expected_time = tzinfo.fromutc(localized_time)
-        return desired_expected_time  # type: ignore[return-value]  # https://github.com/ni/nidaqmx-python/issues/860
+        std_datetime_result = tzinfo.fromutc(localized_time)
+        desired_expected_time = ht_datetime(
+            std_datetime_result.year,
+            std_datetime_result.month,
+            std_datetime_result.day,
+            std_datetime_result.hour,
+            std_datetime_result.minute,
+            std_datetime_result.second,
+            std_datetime_result.microsecond,
+            std_datetime_result.femtosecond,
+            tzinfo=std_datetime_result.tzinfo,
+        )
+        return desired_expected_time
 
     # if the tzinfo passed in is a timedelta function, then we don't need to consider daylight savings  # noqa: W505 - doc line too long (102 > 100 characters) (auto-generated noqa)
     elif tzinfo.utcoffset(None) is not None:

tests/unit/test_lib_time.py

@@ -7,6 +7,7 @@
 from hightime import datetime as ht_datetime
 
 from nidaqmx._lib_time import AbsoluteTime as LibTimestamp
+from nidaqmx._time import _convert_to_desired_timezone
 from tests.unit._time_utils import (
     JAN_01_1850_DATETIME,
     JAN_01_1850_HIGHTIME,
@@ -106,6 +107,37 @@ def test___utc_datetime___convert_to_timestamp_with_dst___is_reversible(date):
     assert astimezone_date == roundtrip_dt
 
 
+@pytest.mark.parametrize(
+    "base_dt, femtosecond, subseconds",
+    [
+        (ht_datetime(2023, 3, 12, tzinfo=timezone.utc), 0, 0),
+        (ht_datetime(2023, 3, 12, tzinfo=timezone.utc), 1, 0x480F),
+        (ht_datetime(2023, 6, 1, tzinfo=timezone.utc), 0, 0),
+        (ht_datetime(2023, 6, 1, tzinfo=timezone.utc), 1, 0x480F),
+        (ht_datetime(2023, 11, 5, tzinfo=timezone.utc), 0, 0),
+        (ht_datetime(2023, 11, 5, tzinfo=timezone.utc), 1, 0x480F),
+    ],
+)
+def test___datetime_with_dst_and_femtoseconds___convert_to_timestamp___is_reversible(
+    base_dt, femtosecond, subseconds
+):
+    target_timezone = ZoneInfo("America/Los_Angeles")
+    from_dt = base_dt.replace(femtosecond=femtosecond)
+    expected_la_time = _convert_to_desired_timezone(from_dt, target_timezone)
+
+    ts = LibTimestamp.from_datetime(from_dt)
+    roundtrip_dt = ts.to_datetime(tzinfo=target_timezone)
+
+    assert ts.msb == LibTimestamp.from_datetime(expected_la_time).msb
+    assert ts.lsb == subseconds
+    # comparison is tricky since imprecision in the conversion to NI-BTF are
+    # caught by the higher precision values in hightime, so we round here.
+    roundtrip_dt_femtosecond = roundtrip_dt.femtosecond
+    if roundtrip_dt.yoctosecond > LibTimestamp.MAX_YS / 2:
+        roundtrip_dt_femtosecond += 1
+    assert roundtrip_dt_femtosecond == femtosecond
+
+
 @pytest.mark.parametrize(
     "datetime_cls, tzinfo, expected_offset",
     [