[ios, macos] Try to make darwin "resolvedLocale" BCP 47 compliant

2 files changed, 13 insertions, 7 deletions

diff --git a/platform/darwin/src/collator.mm b/platform/darwin/src/collator.mm
index 5a87ab3c9a..6b6519d4b1 100644
--- a/platform/darwin/src/collator.mm
+++ b/platform/darwin/src/collator.mm
@@ -11,11 +11,11 @@ namespace expression {
 class Collator::Impl {
 public:
     Impl(bool caseSensitive, bool diacriticSensitive, optional<std::string> locale_)
-    : options((caseSensitive ? 0 : NSCaseInsensitiveSearch) |
-              (diacriticSensitive ? 0 : NSDiacriticInsensitiveSearch))
-    , locale(locale_ ?
-                [[NSLocale alloc] initWithLocaleIdentifier:@((*locale_).c_str())] :
-                [NSLocale currentLocale])
+        : options((caseSensitive ? 0 : NSCaseInsensitiveSearch) |
+                  (diacriticSensitive ? 0 : NSDiacriticInsensitiveSearch))
+        , locale(locale_ ?
+                    [[NSLocale alloc] initWithLocaleIdentifier:@((*locale_).c_str())] :
+                    [NSLocale currentLocale])
     {}
 
     bool operator==(const Impl& other) const {
@@ -35,7 +35,13 @@ public:
     }
 
     std::string resolvedLocale() const {
-        return [locale localeIdentifier].UTF8String;
+        // Following documentation at:
+        // https://developer.apple.com/library/archive/documentation/MacOSX/Conceptual/BPInternational/LanguageandLocaleIDs/LanguageandLocaleIDs.html#//apple_ref/doc/uid/10000171i-CH15-SW9
+        // We expect NSLocale to accept BCP 47 tags as localeIdentifier inputs, but the output format
+        // may append the region tag with an "_". Changing that to a "-" makes the identifier BCP 47 compliant.
+        // Experimentally, "zh-Hans-HK" and "zh-Hans_HK" both round trip -- if the second is used by
+        //  `currentLocale`, we don't want to return the underscore.
+        return [[locale localeIdentifier] stringByReplacingOccurrencesOfString:@"_" withString:@"-"].UTF8String;
     }
 private:
     NSStringCompareOptions options;
diff --git a/platform/node/test/ignores.json b/platform/node/test/ignores.json
index f3fad90ea8..148469ef3a 100644
--- a/platform/node/test/ignores.json
+++ b/platform/node/test/ignores.json
@@ -1,7 +1,7 @@
 {
   "expression-tests/collator/accent-equals-de": "Locale-specific behavior changes based on platform.",
   "expression-tests/is-supported-script/default": "This tests RTL text plugin behavior specific to GL JS",
-  "expression-tests/resolved-locale/basic": "https://github.com/mapbox/mapbox-gl-native/issues/11692",
+  "expression-tests/resolved-locale/basic": "Even the 'en' locale may not be present on some test systems.",
   "query-tests/geometry/multilinestring": "needs investigation",
   "query-tests/geometry/multipolygon": "needs investigation",
   "query-tests/geometry/polygon": "needs investigation",