Handle the sr-Cyrl-ME -> sr-ME collation-only fallback

provider/data/collator/fingerprints.csv

@@ -119,7 +119,7 @@ collation/metadata/v1, vi, -> ee
 collation/metadata/v1, vi/trad, -> ee
 collation/metadata/v1, wo, -> af
 collation/metadata/v1, yo, -> af
-collation/reordering/v1, <lookup>, 320B, 59 identifiers
+collation/reordering/v1, <lookup>, 348B, 60 identifiers
 collation/reordering/v1, <total>, 9464B, 8024B, 30 unique payloads
 collation/reordering/v1, am, 320B, 272B, 3989bb25c1c894c
 collation/reordering/v1, ar, 312B, 264B, 44ac22224ef1784d
@@ -167,6 +167,7 @@ collation/reordering/v1, ru, -> be
 collation/reordering/v1, si, 316B, 268B, 76e6c2377e3f318f
 collation/reordering/v1, si/dict, -> si
 collation/reordering/v1, sr, -> be
+collation/reordering/v1, sr-Cyrl-ME, -> az
 collation/reordering/v1, sr-Latn, -> az
 collation/reordering/v1, ta, 316B, 268B, b337e265c95fe58e
 collation/reordering/v1, te, 316B, 268B, 53be041ee9b02cf9
@@ -182,7 +183,7 @@ collation/reordering/v1, und-Hant, -> und-Hani/stroke
 collation/reordering/v1, ur, -> ar
 collation/root/v1, <singleton>, 131040B, 130923B, 787ce37ea65e1e9
 collation/special/primaries/v1, <singleton>, 72B, 42B, 46181a77c61fe445
-collation/tailoring/v1, <lookup>, 608B, 102 identifiers
+collation/tailoring/v1, <lookup>, 618B, 103 identifiers
 collation/tailoring/v1, <total>, 920210B, 908458B, 93 unique payloads
 collation/tailoring/v1, af, 1004B, 877B, 8e3ca7ba0c0efe4b
 collation/tailoring/v1, ar, 8112B, 7987B, f87603c60cb612d4
@@ -260,6 +261,7 @@ collation/tailoring/v1, sk, 968B, 842B, ab8b5cec368b01e7
 collation/tailoring/v1, sl, 1112B, 985B, 3d4815266923b35f
 collation/tailoring/v1, sq, 1144B, 1018B, 60fb9f14b8173e05
 collation/tailoring/v1, sr, -> bs-Cyrl
+collation/tailoring/v1, sr-Cyrl-ME, -> bs
 collation/tailoring/v1, sr-Latn, -> bs
 collation/tailoring/v1, sv, 1742B, 1616B, 7ec4028488f2d504
 collation/tailoring/v1, sv/trad, 1742B, 1616B, 31420d06d80b25bb

provider/source/src/collator/mod.rs

@@ -9,7 +9,10 @@ use crate::IterableDataProviderCached;
 use crate::SourceDataProvider;
 use icu::collator::provider::*;
 use icu::collections::codepointtrie::CodePointTrie;
-use icu::locale::subtags::{language, script};
+use icu::locale::{
+    locale,
+    subtags::{language, script},
+};
 #[cfg(any(feature = "use_wasm", feature = "use_icu4c"))]
 use icu_codepointtrie_builder::CodePointTrieBuilder;
 use icu_provider::prelude::*;
@@ -30,16 +33,19 @@ fn id_to_file_name(id: DataIdentifierBorrowed) -> String {
             .replace("posix", "POSIX")
     };
 
-    // und-Hant -> zh_stroke
-    // und-Hans -> zh_pinyin
-    // und-Hani/x -> zh_x
+    // und_Hant -> zh_stroke
+    // und_Hans -> zh_pinyin
+    // und_Hani/x -> zh_x
+    // sr_Cyrl_ME -> sr_Latn
 
     if s == "und_Hant" {
         return "zh_stroke".into();
     } else if s == "und_Hans" {
         return "zh_pinyin".into();
     } else if s == "und_Hani" {
         s = "zh".into();
+    } else if s == "sr_Cyrl_ME" {
+        s = "sr_Latn".into();
     }
 
     s.push('_');
@@ -53,7 +59,7 @@ fn id_to_file_name(id: DataIdentifierBorrowed) -> String {
     s
 }
 
-fn file_name_to_id(file_name: &str) -> Vec<DataIdentifierCow<'static>> {
+fn file_name_to_ids(file_name: &str) -> Vec<DataIdentifierCow<'static>> {
     let (mut language, mut variant) = file_name.rsplit_once('_').unwrap();
     if language == "root" {
         language = "und";
@@ -72,19 +78,27 @@ fn file_name_to_id(file_name: &str) -> Vec<DataIdentifierCow<'static>> {
             // Pinyin is stored in both und-Hans and und-Hani/pinyin
             r.push(DataIdentifierCow::from_borrowed_and_owned(
                 Default::default(),
-                "und-Hans".parse().unwrap(),
+                locale!("und-Hans").into(),
             ));
         } else if variant == "stroke" {
             // Stroke is stored in both und-Hans and und-Hani/stroke
             r.push(DataIdentifierCow::from_borrowed_and_owned(
                 Default::default(),
-                "und-Hant".parse().unwrap(),
+                locale!("und-Hant").into(),
             ));
         }
     } else if variant == "standard" {
         variant = "";
     }
 
+    if language == "sr_Latn" {
+        // sr-Cyrl-ME falls back to sr-ME, which falls back to sr-Latn.
+        r.push(DataIdentifierCow::from_borrowed_and_owned(
+            Default::default(),
+            locale!("sr-Cyrl-ME").into(),
+        ));
+    }
+
     let marker_attributes = match variant {
         "traditional" => DataMarkerAttributes::from_str_or_panic("trad").to_owned(),
         "phonebook" => DataMarkerAttributes::from_str_or_panic("phonebk").to_owned(),
@@ -99,6 +113,35 @@ fn file_name_to_id(file_name: &str) -> Vec<DataIdentifierCow<'static>> {
     r
 }
 
+#[test]
+fn test_all_fallback_overrides_handled() {
+    let provider = SourceDataProvider::new_testing();
+    let required_overrides = provider
+        .cldr()
+        .unwrap()
+        .core()
+        .read_and_parse::<super::cldr_serde::parent_locales::Resource>(
+            "supplemental/parentLocales.json",
+        )
+        .unwrap()
+        .supplemental
+        .parent_locales
+        .collations
+        .keys()
+        .collect::<Vec<_>>();
+
+    let handled_overrides = [
+        "sr-Cyrl-ME",
+        "yue",
+        "yue-CN",
+        "yue-Hans",
+        "yue-Hans-CN",
+        "yue-Hant",
+    ];
+
+    assert_eq!(required_overrides, handled_overrides);
+}
+
 impl SourceDataProvider {
     fn load_toml<T>(&self, id: DataIdentifierBorrowed, suffix: &str) -> Result<&T, DataError>
     where
@@ -130,7 +173,7 @@ impl SourceDataProvider {
                     file_name
                 })
             })
-            .flat_map(|s| file_name_to_id(&s))
+            .flat_map(|s| file_name_to_ids(&s))
             .collect())
     }
 }