[Variant] Align cast logic related to utf8 with arrow-cast kernel

arrow-cast/src/display.rs

@@ -733,7 +733,8 @@ macro_rules! decimal_display {
 
 decimal_display!(Decimal32Type, Decimal64Type, Decimal128Type, Decimal256Type);
 
-fn write_timestamp(
+/// Writes a timestamp value to the output using the given representation.
+pub fn write_timestamp(
     f: &mut dyn Write,
     naive: NaiveDateTime,
     timezone: Option<Tz>,

arrow-cast/src/parse.rs

@@ -611,7 +611,14 @@ fn parse_extended_ymd(string: &str) -> Option<(i32, u32, u32)> {
     Some((year, month, day))
 }
 
-fn parse_date(string: &str) -> Option<NaiveDate> {
+/// Parse a given date string into a `NaiveDate`.
+///
+/// Supports:
+/// - ISO date strings: `"2026-06-10"`, `"2026-6-9"`, `"2026-06-9"`, `"2026-6-09"`
+/// - ISO extended (signed) year date strings: `"+2026-06-10"`, `"-2026-06-10"`
+/// - No hyphen date strings: `"20260610"`
+/// - Datetime strings:`"2026-06-10T14:23:45"`
+pub fn parse_date(string: &str) -> Option<NaiveDate> {
     // If the date has an extended (signed) year such as "+10999-12-31" or "-0012-05-06"
     //
     // According to [ISO 8601], years have:

parquet-variant-compute/src/shred_variant.rs

@@ -92,6 +92,7 @@ pub(crate) fn shred_variant_with_options(
         cast_options,
         array.len(),
         NullValue::TopLevelVariant,
+        true,
     )?;
     for i in 0..array.len() {
         if array.is_null(i) {
@@ -145,6 +146,7 @@ pub(crate) fn make_variant_to_shredded_variant_arrow_row_builder<'a>(
     cast_options: &'a CastOptions,
     capacity: usize,
     null_value: NullValue,
+    shred: bool,
 ) -> Result<VariantToShreddedVariantRowBuilder<'a>> {
     let builder = match data_type {
         DataType::Struct(fields) => {
@@ -193,7 +195,7 @@ pub(crate) fn make_variant_to_shredded_variant_arrow_row_builder<'a>(
         | DataType::FixedSizeBinary(16) // UUID
         => {
             let builder =
-                make_primitive_variant_to_arrow_row_builder(data_type, cast_options, capacity)?;
+                make_primitive_variant_to_arrow_row_builder(data_type, cast_options, capacity, shred)?;
             let typed_value_builder =
                 VariantToShreddedPrimitiveVariantRowBuilder::new(builder, capacity, null_value);
             VariantToShreddedVariantRowBuilder::Primitive(typed_value_builder)
@@ -376,6 +378,7 @@ impl<'a> VariantToShreddedObjectVariantRowBuilder<'a> {
                 cast_options,
                 capacity,
                 NullValue::ObjectField,
+                true,
             )?;
             Ok((field.name().as_str(), builder))
         });
@@ -1046,6 +1049,7 @@ mod tests {
                 &cast_options,
                 1,
                 mode,
+                true,
             )
             .unwrap();
             primitive_builder.append_null().unwrap();
@@ -1076,6 +1080,7 @@ mod tests {
                 &cast_options,
                 1,
                 mode,
+                true,
             )
             .unwrap();
             array_builder.append_null().unwrap();
@@ -1104,6 +1109,7 @@ mod tests {
                 &cast_options,
                 1,
                 mode,
+                true,
             )
             .unwrap();
             object_builder.append_null().unwrap();