From 52a0ab1530ed4c343e293ff5f928ea715ad213c9 Mon Sep 17 00:00:00 2001
From: "Shane F. Carr" <shane@unicode.org>
Date: Wed, 6 Dec 2023 14:54:24 -0800
Subject: [PATCH] Add data loading for date pattern to TypedDateTimePattern

---
 components/datetime/src/pattern/mod.rs |  2 +-
 components/datetime/src/pattern/neo.rs | 71 ++++++++++++++++++++++++--
 2 files changed, 68 insertions(+), 5 deletions(-)

diff --git a/components/datetime/src/pattern/mod.rs b/components/datetime/src/pattern/mod.rs
index 529eb7e956e..3053b21deff 100644
--- a/components/datetime/src/pattern/mod.rs
+++ b/components/datetime/src/pattern/mod.rs
@@ -7,7 +7,7 @@ mod error;
 pub mod hour_cycle;
 mod item;
 #[cfg(feature = "experimental")]
-mod neo;
+pub mod neo;
 pub mod reference;
 pub mod runtime;
 
diff --git a/components/datetime/src/pattern/neo.rs b/components/datetime/src/pattern/neo.rs
index 7423f109bb6..4705d7074e1 100644
--- a/components/datetime/src/pattern/neo.rs
+++ b/components/datetime/src/pattern/neo.rs
@@ -2,14 +2,17 @@
 // called LICENSE at the top level of the ICU4X source tree
 // (online at: https://github.com/unicode-org/icu4x/blob/main/LICENSE ).
 
-use core::{marker::PhantomData, str::FromStr};
+use core::marker::PhantomData;
+use core::str::FromStr;
 
 use super::{runtime, PatternError};
 use crate::options::length;
+use crate::provider::neo::*;
+use crate::CldrCalendar;
 use crate::Error;
-use crate::{provider::neo::*, CldrCalendar};
 use icu_provider::prelude::*;
 
+#[derive(Debug)]
 enum DateTimePatternInner {
     Custom(runtime::Pattern<'static>),
     Date(DataPayload<ErasedDatePatternV1Marker>),
@@ -21,6 +24,7 @@ enum DateTimePatternInner {
     },
 }
 
+#[derive(Debug)]
 pub struct TypedDateTimePattern<C: CldrCalendar> {
     inner: DateTimePatternInner,
     _calendar: PhantomData<C>,
@@ -35,6 +39,55 @@ impl<C: CldrCalendar> TypedDateTimePattern<C> {
         })
     }
 
+    /// Loads a [`TypedDateTimePattern`] for a date length.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// use icu::calendar::Gregorian;
+    /// use icu::datetime::pattern::neo::TypedDateTimePattern;
+    /// use icu::datetime::options::length;
+    /// use icu::locid::locale;
+    ///
+    /// let expected_pattern = TypedDateTimePattern::<Gregorian>::try_from_pattern_str("d MMM y").unwrap();
+    /// let actual_pattern = TypedDateTimePattern::<Gregorian>::try_new_date_with_length_unstable(
+    ///     &icu::datetime::provider::Baked,
+    ///     &locale!("fr").into(),
+    ///     length::Date::Medium,
+    /// ).unwrap();
+    ///
+    /// assert_eq!(expected_pattern, actual_pattern);
+    /// ```
+    pub fn try_new_date_with_length_unstable<P>(
+        provider: &P,
+        locale: &DataLocale,
+        length: length::Date,
+    ) -> Result<Self, Error>
+    where
+        P: DataProvider<C::DatePatternV1Marker> + ?Sized,
+    {
+        let mut locale = locale.clone();
+        locale.set_aux(AuxiliaryKeys::from_subtag(aux::pattern_subtag_for(
+            match length {
+                length::Date::Full => aux::PatternLength::Full,
+                length::Date::Long => aux::PatternLength::Long,
+                length::Date::Medium => aux::PatternLength::Medium,
+                length::Date::Short => aux::PatternLength::Short,
+            },
+            None, // no hour cycle for date patterns
+        )));
+        let payload = provider
+            .load(DataRequest {
+                locale: &locale,
+                metadata: Default::default(),
+            })?
+            .take_payload()?;
+        Ok(Self {
+            inner: DateTimePatternInner::Date(payload.cast()),
+            _calendar: PhantomData,
+        })
+    }
+
     pub(crate) fn as_borrowed(&self) -> DateTimePatternBorrowed {
         let borrowed_inner = match self.inner {
             DateTimePatternInner::Custom(ref pattern) => {
@@ -69,7 +122,17 @@ impl<C: CldrCalendar> FromStr for TypedDateTimePattern<C> {
     }
 }
 
-#[derive(Debug, Copy, Clone)]
+// Check equality on the borrowed variant since it flattens the difference
+// between the three `Single`` pattern variants, which is not public-facing
+impl<C: CldrCalendar> PartialEq for TypedDateTimePattern<C> {
+    fn eq(&self, other: &Self) -> bool {
+        self.as_borrowed().eq(&other.as_borrowed())
+    }
+}
+
+impl<C: CldrCalendar> Eq for TypedDateTimePattern<C> {}
+
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
 enum DateTimePatternBorrowedInner<'a> {
     Single(&'a runtime::Pattern<'a>),
     DateTime {
@@ -80,7 +143,7 @@ enum DateTimePatternBorrowedInner<'a> {
 }
 
 // Not clear if this needs to be public. For now, make it private.
-#[derive(Debug, Copy, Clone)]
+#[derive(Debug, Copy, Clone, PartialEq, Eq)]
 pub(crate) struct DateTimePatternBorrowed<'a> {
     inner: DateTimePatternBorrowedInner<'a>,
 }