fix: fix roundtrip conversion for LocalDateTime type (#624)

Author: badmonster0

python/cocoindex/tests/test_convert.py

@@ -198,14 +198,19 @@ def test_encode_engine_value_none() -> None:
     assert encode_engine_value(None) is None
 
 
-def test_make_engine_value_decoder_basic_types() -> None:
+def test_roundtrip_basic_types() -> None:
     validate_full_roundtrip(42, int)
     validate_full_roundtrip(3.25, float, (3.25, Float64))
     validate_full_roundtrip(3.25, Float64, (3.25, float))
     validate_full_roundtrip(3.25, Float32)
     validate_full_roundtrip("hello", str)
     validate_full_roundtrip(True, bool)
     validate_full_roundtrip(False, bool)
+    validate_full_roundtrip(datetime.date(2025, 1, 1), datetime.date)
+    validate_full_roundtrip(datetime.datetime.now(), cocoindex.LocalDateTime)
+    validate_full_roundtrip(
+        datetime.datetime.now(datetime.UTC), cocoindex.OffsetDateTime
+    )
 
 
 @pytest.mark.parametrize(

src/base/value.rs

@@ -883,7 +883,9 @@ impl serde::Serialize for BasicValue {
             BasicValue::Uuid(v) => serializer.serialize_str(&v.to_string()),
             BasicValue::Date(v) => serializer.serialize_str(&v.to_string()),
             BasicValue::Time(v) => serializer.serialize_str(&v.to_string()),
-            BasicValue::LocalDateTime(v) => serializer.serialize_str(&v.to_string()),
+            BasicValue::LocalDateTime(v) => {
+                serializer.serialize_str(&v.format("%Y-%m-%dT%H:%M:%S%.6f").to_string())
+            }
             BasicValue::OffsetDateTime(v) => {
                 serializer.serialize_str(&v.to_rfc3339_opts(chrono::SecondsFormat::AutoSi, true))
             }