Add initial neo datetime FFI

components/datetime/src/builder.rs

@@ -357,10 +357,6 @@ pub struct FieldSetBuilder {
     pub year_style: Option<YearStyle>,
 }
 
-// This is the default length when the builder is used. This could have been defined in the macro
-// that generates the `take_from_builder` fns, but it would be easily lost.
-pub(crate) const DEFAULT_LENGTH: Length = Length::Medium;
-
 enum DateOrCalendarPeriodFieldSet {
     Date(DateFieldSet),
     CalendarPeriod(CalendarPeriodFieldSet),

components/datetime/src/fieldsets.rs

@@ -239,13 +239,12 @@ macro_rules! impl_marker_with_options {
                 }
             }
             /// Builds this field set, removing the needed options from the builder.
-            /// If length is needed but is None, falls back to `builder::DEFAULT_LENGTH`.
             #[allow(unused)]
             pub(crate) fn take_from_builder(
                 options: &mut builder::FieldSetBuilder
             ) -> Self {
                 Self {
-                    $(length: yes_to!(options.length.take().unwrap_or(builder::DEFAULT_LENGTH), $sample_length),)?
+                    $(length: yes_to!(options.length.take().unwrap_or_default(), $sample_length),)?
                     $(alignment: yes_to!(options.alignment.take(), $alignment_yes),)?
                     $(year_style: yes_to!(options.year_style.take(), $yearstyle_yes),)?
                     $(time_precision: yes_to!(options.time_precision.take(), $timeprecision_yes),)?

components/datetime/src/options/mod.rs

@@ -58,7 +58,7 @@ use crate::neo_serde::TimePrecisionSerde;
 ///     "January 1, 2000"
 /// );
 /// ```
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Default)]
 #[cfg_attr(
     all(feature = "serde", feature = "experimental"),
     derive(serde::Serialize, serde::Deserialize)
@@ -73,6 +73,9 @@ pub enum Length {
     /// A long date; typically spelled-out, as in “January 1, 2000”.
     Long = 4,
     /// A medium-sized date; typically abbreviated, as in “Jan. 1, 2000”.
+    ///
+    /// This is the default.
+    #[default]
     Medium = 3,
     /// A short date; typically numeric, as in “1/1/2000”.
     Short = 1,
@@ -128,7 +131,7 @@ impl IntoOption<Length> for Length {
 ///     "01/01/25"
 /// );
 /// ```
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Default)]
 #[cfg_attr(
     all(feature = "serde", feature = "experimental"),
     derive(serde::Serialize, serde::Deserialize)
@@ -142,6 +145,7 @@ pub enum Alignment {
     /// Align fields as the locale specifies them to be aligned.
     ///
     /// This is the default option.
+    #[default]
     Auto,
     /// Align fields as appropriate for a column layout. For example:
     ///
@@ -257,7 +261,7 @@ impl IntoOption<Alignment> for Alignment {
 ///     "1/1/2025 AD"
 /// );
 /// ```
-#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq, Hash, Default)]
 #[cfg_attr(
     all(feature = "serde", feature = "experimental"),
     derive(serde::Serialize, serde::Deserialize)
@@ -279,6 +283,7 @@ pub enum YearStyle {
     /// - `77 AD`
     /// - `1900`
     /// - `'24`
+    #[default]
     Auto,
     /// Always display the century, and display the era when needed to
     /// disambiguate the year, based on locale preferences.

components/datetime/src/raw/neo.rs

@@ -224,7 +224,7 @@ impl DatePatternSelectionData {
     pub(crate) fn select(&self, input: &ExtractedInput) -> DatePatternDataBorrowed {
         match self {
             DatePatternSelectionData::SkeletonDate { options, payload } => {
-                let year_style = options.year_style.unwrap_or(YearStyle::Auto);
+                let year_style = options.year_style.unwrap_or_default();
                 let variant = match (
                     year_style,
                     input
@@ -870,7 +870,8 @@ impl<'a> ItemsAndOptions<'a> {
             #[allow(clippy::single_match)] // need `ref mut`, which doesn't work in `if let`?
             match &mut pattern_item {
                 PatternItem::Field(ref mut field) => {
-                    if matches!(self.alignment, Some(Alignment::Column))
+                    let alignment = self.alignment.unwrap_or_default();
+                    if matches!(alignment, Alignment::Column)
                         && field.length == FieldLength::One
                         && matches!(
                             field.symbol,