ICU-22923 Workaround for addLikelySubtags(und-Latn-RS) bug

Author: mihnita

icu4c/source/data/misc/langInfo.txt

@@ -2444,9 +2444,9 @@ da{
         }
         pressure{
             inch-ofhg{
-                dnam{"# Hg"}
-                one{"{0} # Hg"}
-                other{"{0} # Hg"}
+                dnam{"″ Hg"}
+                one{"{0} ″ Hg"}
+                other{"{0} ″ Hg"}
             }
             millimeter-ofhg{
                 dnam{"mmHg"}

icu4c/source/data/unit/da.txt

@@ -5923,11 +5923,6 @@ testLikelySubtagsLineFn(void *context,
         return;
     }
 
-    if ((uprv_strcmp(source.c_str(), "und-Latn-RS") == 0 )
-        && THIS->logKnownIssue("ICU-22976", "unexpected likely subtags for und-Latn-RS")) {
-      return;
-    }
-
     Locale actualMax(l);
     actualMax.addLikelySubtags(*pErrorCode);
     if (addLikely == "FAIL") {

icu4c/source/test/intltest/loctest.cpp

@@ -5723,13 +5723,9 @@ public void likelySubtagsDataDriven(TestCase test) {
             assertEquals("addLikelySubtags(" + test.source + ") should be unchanged",
                 l, ULocale.addLikelySubtags(l));
         } else {
-            if (test.source.equals("und-Latn-RS")
-                && logKnownIssue("ICU-23052", "addLikelySubtags(und-Latn-RS) bug") ) {
-              return;
-                }
-              assertEquals("addLikelySubtags(" + test.source + ")",
-                  test.addLikely, ULocale.addLikelySubtags(l).toLanguageTag());
-              }
+            assertEquals("addLikelySubtags(" + test.source + ")",
+                test.addLikely, ULocale.addLikelySubtags(l).toLanguageTag());
+        }
         if (test.removeFavorRegion.equals("FAIL")) {
             assertEquals("minimizeSubtags(" + test.source + ") should be unchanged",
                 l, ULocale.minimizeSubtags(l));

icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/util/ULocaleTest.java

@@ -270,8 +270,10 @@ private static Map<String, Map<String, Map<String, LSR>>> makeTable(
 
         // Add the special case for "und-Latn" => "en-Latn-US" (which is a bit of a
         // hack for language matching).
-        // TODO: Find out the history of this line and document it better.
+        // Temporary patch. Needs an update of the ICU algorithm to match CLDR.
+        // See https://unicode-org.atlassian.net/browse/ICU-23052
         set(lsrTable, "und", "Latn", "", lsr("en", "Latn", "US"));
+        set(lsrTable, "und", "Latn", "RS", lsr("sr", "Latn", "RS"));
         logger.fine(lsrTable::toString);
 
         // Ensure that if "und-RR" => "ll-Ssss-RR", then we also add "Ssss" => "RR".