Convert preferences to DataLocale

components/list/src/list_formatter.rs

@@ -58,12 +58,13 @@ macro_rules! constructor {
                 ListLength::Short => ListFormatterPatternsV2::SHORT,
                 ListLength::Wide => ListFormatterPatternsV2::WIDE,
             };
-            let locale = get_data_locale_from_prefs(prefs);
+            let locale = DataLocale::from_preferences_locale::<$marker>(prefs.locale_prefs);
             let data = provider
                 .load(DataRequest {
                     id: DataIdentifierBorrowed::for_marker_attributes_and_locale(
                         length,
-                        &locale),
+                        &locale
+                    ),
                     ..Default::default()
                 })?
                 .payload
@@ -73,17 +74,6 @@ macro_rules! constructor {
     };
 }
 
-fn get_data_locale_from_prefs(prefs: ListFormatterPreferences) -> DataLocale {
-    // TODO(#5764): This should utilize region source priority.
-    DataLocale::from_subtags(
-        prefs.locale_prefs.language,
-        prefs.locale_prefs.script,
-        prefs.locale_prefs.region,
-        prefs.locale_prefs.variant,
-        prefs.locale_prefs.subdivision,
-    )
-}
-
 impl ListFormatter {
     constructor!(
         try_new_and,

components/locale_core/src/preferences/mod.rs

@@ -529,13 +529,12 @@ macro_rules! __define_preferences {
             }
         }
 
-        impl $name {
-            /// Constructs a `Locale` corresponding to these preferences.
-            pub fn into_locale(self) -> $crate::Locale {
+        impl From<$name> for $crate::Locale {
+            fn from(other: $name) -> Self {
                 use $crate::preferences::PreferenceKey;
-                let mut result = $crate::Locale::from(self.locale_prefs);
+                let mut result = Self::from(other.locale_prefs);
                 $(
-                    if let Some(value) = &self.$key {
+                    if let Some(value) = other.$key {
                         if let Some(ue) = <$pref>::unicode_extension_key() {
                             let val = value.unicode_extension_value().unwrap();
                             result.extensions.unicode.keywords.set(ue, val);
@@ -544,7 +543,9 @@ macro_rules! __define_preferences {
                 )*
                 result
             }
+        }
 
+        impl $name {
             /// Extends the preferences with the values from another set of preferences.
             pub fn extend(&mut self, other: $name) {
                 self.locale_prefs.extend(other.locale_prefs);

ffi/capi/tests/missing_apis.txt

@@ -163,7 +163,6 @@ icu::list::ListFormatterOptions::default#FnInStruct
 icu::list::ListFormatterOptions::with_length#FnInStruct
 icu::list::ListFormatterPreferences#Struct
 icu::list::ListFormatterPreferences::extend#FnInStruct
-icu::list::ListFormatterPreferences::into_locale#FnInStruct
 icu::locale::preferences::LocalePreferences#Struct
 icu::locale::preferences::LocalePreferences::default#FnInStruct
 icu::locale::preferences::LocalePreferences::extend#FnInStruct

provider/core/src/request.rs

@@ -18,6 +18,9 @@ use icu_locale_core::subtags::{Language, Region, Script, Subtag, Variant};
 use icu_locale_core::{LanguageIdentifier, Locale, ParseError};
 use zerovec::ule::VarULE;
 
+use crate::fallback::LocaleFallbackPriority;
+use crate::DataMarker;
+
 /// The request type passed into all data provider implementations.
 #[derive(Default, Debug, Clone, Copy, PartialEq, Eq)]
 #[allow(clippy::exhaustive_structs)] // this type is stable
@@ -277,20 +280,26 @@ impl DataLocale {
         )
     }
 
-    /// Creates a [`DataLocale`] from a list of subtags.
-    pub const fn from_subtags(
-        language: Language,
-        script: Option<Script>,
-        region: Option<Region>,
-        variant: Option<Variant>,
-        subdivision: Option<Subtag>,
+    /// Returns a [`DataLocale`] usable for the marker `M`.
+    pub const fn from_preferences_locale<M: DataMarker>(
+        locale: icu_locale_core::preferences::LocalePreferences,
     ) -> Self {
         Self {
-            language,
-            script,
-            region,
-            variant,
-            subdivision,
+            language: locale.language,
+            script: locale.script,
+            region: match (locale.region, locale.ue_region) {
+                (Some(_), Some(r))
+                    if matches!(
+                        M::INFO.fallback_config.priority,
+                        LocaleFallbackPriority::Region
+                    ) =>
+                {
+                    Some(r)
+                }
+                (r, _) => r,
+            },
+            variant: locale.variant,
+            subdivision: locale.subdivision,
 
             keywords: unicode_ext::Keywords::new(),
         }