Cherry-pick: ICU-22742 Fix handling of XA,XB,XC for addLikelySubtags

Upstream commit:
https://github.com/unicode-org/icu/pull/2977/commits/78502b61366731c5483e48d2e746742e5962632e
Upstream bug:
https://unicode-org.atlassian.net/browse/ICU-22742

Add more tests.
ICU-22742 Add PS... variants
ICU-22742 Add java tests
ICU-22742 extend tests
ICU-22742 wrap java

Bug: 331740612
Test: atest CtsIcuTestCases CtsIcu4cTestCases
Change-Id: I91546706f5918ac353c0bf779ba6f16c0a0a1c5d

8 files changed, 502 insertions, 151 deletions

diff --git a/android_icu4j/src/main/java/android/icu/impl/locale/LikelySubtags.java b/android_icu4j/src/main/java/android/icu/impl/locale/LikelySubtags.java
index ffc3a7413..6c4b699c9 100644
--- a/android_icu4j/src/main/java/android/icu/impl/locale/LikelySubtags.java
+++ b/android_icu4j/src/main/java/android/icu/impl/locale/LikelySubtags.java
@@ -220,49 +220,42 @@ public final class LikelySubtags {
         // Handle pseudolocales like en-XA, ar-XB, fr-PSCRACK.
         // They should match only themselves,
         // not other locales with what looks like the same language and script subtags.
-        if (region.length() == 2 && region.charAt(0) == 'X') {
-            switch (region.charAt(1)) {
-            case 'A':
-                if (returnInputIfUnmatch) {
-                    return new LSR(language, script, region, LSR.EXPLICIT_LSR);
-                }
-                return new LSR(PSEUDO_ACCENTS_PREFIX + language,
-                        PSEUDO_ACCENTS_PREFIX + script, region, LSR.EXPLICIT_LSR);
-            case 'B':
-                if (returnInputIfUnmatch) {
-                    return new LSR(language, script, region, LSR.EXPLICIT_LSR);
-                }
-                return new LSR(PSEUDO_BIDI_PREFIX + language,
-                        PSEUDO_BIDI_PREFIX + script, region, LSR.EXPLICIT_LSR);
-            case 'C':
-                if (returnInputIfUnmatch) {
-                    return new LSR(language, script, region, LSR.EXPLICIT_LSR);
+        if (!returnInputIfUnmatch) {
+            if (region.length() == 2 && region.charAt(0) == 'X') {
+                switch (region.charAt(1)) {
+                case 'A':
+                    return new LSR(PSEUDO_ACCENTS_PREFIX + language,
+                            PSEUDO_ACCENTS_PREFIX + script, region, LSR.EXPLICIT_LSR);
+                case 'B':
+                    return new LSR(PSEUDO_BIDI_PREFIX + language,
+                            PSEUDO_BIDI_PREFIX + script, region, LSR.EXPLICIT_LSR);
+                case 'C':
+                    return new LSR(PSEUDO_CRACKED_PREFIX + language,
+                            PSEUDO_CRACKED_PREFIX + script, region, LSR.EXPLICIT_LSR);
+                default:  // normal locale
+                    break;
                 }
-                return new LSR(PSEUDO_CRACKED_PREFIX + language,
-                        PSEUDO_CRACKED_PREFIX + script, region, LSR.EXPLICIT_LSR);
-            default:  // normal locale
-                break;
             }
-        }
 
-        if (variant.startsWith("PS")) {
-            int lsrFlags = region.isEmpty() ?
-                    LSR.EXPLICIT_LANGUAGE | LSR.EXPLICIT_SCRIPT : LSR.EXPLICIT_LSR;
-            switch (variant) {
-            case "PSACCENT":
-                return new LSR(PSEUDO_ACCENTS_PREFIX + language,
-                        PSEUDO_ACCENTS_PREFIX + script,
-                        region.isEmpty() ? "XA" : region, lsrFlags);
-            case "PSBIDI":
-                return new LSR(PSEUDO_BIDI_PREFIX + language,
-                        PSEUDO_BIDI_PREFIX + script,
-                        region.isEmpty() ? "XB" : region, lsrFlags);
-            case "PSCRACK":
-                return new LSR(PSEUDO_CRACKED_PREFIX + language,
-                        PSEUDO_CRACKED_PREFIX + script,
-                        region.isEmpty() ? "XC" : region, lsrFlags);
-            default:  // normal locale
-                break;
+            if (variant.startsWith("PS")) {
+                int lsrFlags = region.isEmpty() ?
+                            LSR.EXPLICIT_LANGUAGE | LSR.EXPLICIT_SCRIPT : LSR.EXPLICIT_LSR;
+                switch (variant) {
+                case "PSACCENT":
+                    return new LSR(PSEUDO_ACCENTS_PREFIX + language,
+                            PSEUDO_ACCENTS_PREFIX + script,
+                            region.isEmpty() ? "XA" : region, lsrFlags);
+                case "PSBIDI":
+                    return new LSR(PSEUDO_BIDI_PREFIX + language,
+                            PSEUDO_BIDI_PREFIX + script,
+                            region.isEmpty() ? "XB" : region, lsrFlags);
+                case "PSCRACK":
+                    return new LSR(PSEUDO_CRACKED_PREFIX + language,
+                            PSEUDO_CRACKED_PREFIX + script,
+                            region.isEmpty() ? "XC" : region, lsrFlags);
+                default:  // normal locale
+                    break;
+                }
             }
         }
 
diff --git a/android_icu4j/src/main/tests/android/icu/dev/test/util/ULocaleTest.java b/android_icu4j/src/main/tests/android/icu/dev/test/util/ULocaleTest.java
index a8fb04a62..be223f7c8 100644
--- a/android_icu4j/src/main/tests/android/icu/dev/test/util/ULocaleTest.java
+++ b/android_icu4j/src/main/tests/android/icu/dev/test/util/ULocaleTest.java
@@ -1975,17 +1975,36 @@ public class ULocaleTest extends CoreTestFmwk {
                     "zh_Hani",
                     "zh_Hani_CN" // If change, please also update ULocale.java
                 }, {
-                    // ICU-22545
-                    "en_XA",
+                    // ICU-22545 & ICU-22742
                     "en_XA",
+                    "en_Latn_XA",
+                }, {
+                    // ICU-22545 & ICU-22742
+                    "ar_XB",
+                    "ar_Arab_XB",
+                }, {
+                    // ICU-22545 & ICU-22742
+                    "ru_XC",
+                    "ru_Cyrl_XC",
+                }, {
+                    // ICU-22742
+                    "en_PSACCENT",
+                    "en_Latn_US_PSACCENT",
+                }, {
+                    "ar_PSBIDI",
+                    "ar_Arab_EG_PSBIDI",
+                }, {
+                    "ru_PSCRACK",
+                    "ru_Cyrl_RU_PSCRACK",
                 }, {
-                    // ICU-22545
-                    "en_XB",
-                    "en_XB",
+                    "ar_PSACCENT",
+                    "ar_Arab_EG_PSACCENT",
                 }, {
-                    // ICU-22545
-                    "en_XC",
-                    "en_XC",
+                    "ru_PSBIDI",
+                    "ru_Cyrl_RU_PSBIDI",
+                }, {
+                    "en_PSCRACK",
+                    "en_Latn_US_PSCRACK",
                 }
         };
 
@@ -5595,6 +5614,103 @@ public class ULocaleTest extends CoreTestFmwk {
         return tests;
     }
 
+    // ICU-22742, test addLikelySubtags with pseudo-locales
+    @Test
+    public void TestPseudoLocales() {
+        // input locale tag, expected locale tag
+        String[][] testCases = new String[][] {
+                // language + region, en
+                { "en-XA", "en-Latn-XA" },
+                { "en-XB", "en-Latn-XB" },
+                { "en-XC", "en-Latn-XC" },
+
+                // language + region, ar
+                { "ar-XA", "ar-Arab-XA" },
+                { "ar-XB", "ar-Arab-XB" },
+                { "ar-XC", "ar-Arab-XC" },
+
+                // language + region, something other than en, ar
+                { "ru-XA", "ru-Cyrl-XA" },
+                { "el-XB", "el-Grek-XB" },
+
+                // undefined language - region
+                { "und-XA", "en-Latn-XA" },
+                { "und-XB", "en-Latn-XB" },
+                { "und-XC", "en-Latn-XC" },
+
+                // language + script + region
+                { "und-Latn-XA", "en-Latn-XA" },
+                { "und-Latn-XB", "en-Latn-XB" },
+                { "und-Latn-XC", "en-Latn-XC" },
+                { "und-Arab-XA", "ar-Arab-XA" },
+                { "und-Arab-XB", "ar-Arab-XB" },
+                { "und-Arab-XC", "ar-Arab-XC" },
+                { "und-Cyrl-XA", "ru-Cyrl-XA" },
+                { "und-Grek-XB", "el-Grek-XB" },
+
+                // Make sure the script is not damaged, when correct
+                { "ru-Cyrl-XA", "ru-Cyrl-XA" },
+                { "el-Grek-XB", "el-Grek-XB" },
+
+                // Make sure the script is not damaged, even if it is wrong
+                { "ru-Grek-XA", "ru-Grek-XA" },
+                { "el-Cyrl-XB", "el-Cyrl-XB" },
+
+                // PS Variants
+                { "en-XA-PSACCENT", "en-Latn-XA-psaccent" },
+                { "en-XA-PSBIDI", "en-Latn-XA-psbidi" },
+                { "en-XA-PSCRACK", "en-Latn-XA-pscrack" },
+                { "ar-XB-PSACCENT", "ar-Arab-XB-psaccent" },
+                { "ar-XB-PSBIDI", "ar-Arab-XB-psbidi" },
+                { "ar-XB-PSCRACK", "ar-Arab-XB-pscrack" },
+                { "en-XC-PSACCENT", "en-Latn-XC-psaccent" },
+                { "en-XC-PSBIDI", "en-Latn-XC-psbidi" },
+                { "en-XC-PSCRACK", "en-Latn-XC-pscrack" },
+
+                { "en-US-PSACCENT", "en-Latn-US-psaccent" },
+                { "en-US-PSBIDI", "en-Latn-US-psbidi" },
+                { "en-US-PSCRACK", "en-Latn-US-pscrack" },
+                { "ar-EG-PSACCENT", "ar-Arab-EG-psaccent" },
+                { "ar-EG-PSBIDI", "ar-Arab-EG-psbidi" },
+                { "ar-EG-PSCRACK", "ar-Arab-EG-pscrack" },
+
+                { "en-PSACCENT", "en-Latn-US-psaccent" },
+                { "en-PSBIDI", "en-Latn-US-psbidi" },
+                { "en-PSCRACK", "en-Latn-US-pscrack" },
+                { "ar-PSACCENT", "ar-Arab-EG-psaccent" },
+                { "ar-PSBIDI", "ar-Arab-EG-psbidi" },
+                { "ar-PSCRACK", "ar-Arab-EG-pscrack" },
+
+                { "und-US-PSACCENT", "en-Latn-US-psaccent" },
+                { "und-US-PSBIDI", "en-Latn-US-psbidi" },
+                { "und-US-PSCRACK", "en-Latn-US-pscrack" },
+                { "und-EG-PSACCENT", "ar-Arab-EG-psaccent" },
+                { "und-EG-PSBIDI", "ar-Arab-EG-psbidi" },
+                { "und-EG-PSCRACK", "ar-Arab-EG-pscrack" },
+
+                { "und-PSACCENT", "en-Latn-US-psaccent" },
+                { "und-PSBIDI", "en-Latn-US-psbidi" },
+                { "und-PSCRACK", "en-Latn-US-pscrack" },
+                { "und-PSACCENT", "en-Latn-US-psaccent" },
+                { "und-PSBIDI", "en-Latn-US-psbidi" },
+                { "und-PSCRACK", "en-Latn-US-pscrack" },
+        };
+        String extensions = "-u-nu-Deva-hc-h23-fw-mon-mu-celsius-x-something-more";
+
+        for (String[] testCase : testCases) {
+            String inputTag = testCase[0];
+            String expectedTag = testCase[1];
+            ULocale result = ULocale.addLikelySubtags(ULocale.forLanguageTag(inputTag));
+            ULocale expected = ULocale.forLanguageTag(expectedTag);
+            assertEquals("pseudo-locales(" + inputTag + ")", expected, result);
+
+            // Make sure this also works with extensions. Kind of hacky...
+            result = ULocale.addLikelySubtags(ULocale.forLanguageTag(inputTag + extensions));
+            expected = ULocale.forLanguageTag(expectedTag + extensions);
+            assertEquals("pseudo-locales(" + inputTag + ")", expected, result);
+        }
+    }
+
     @Test
     @Parameters(method = "readLikelySubtagsTestCases")
     public void likelySubtagsDataDriven(TestCase test) {
diff --git a/icu4c/source/common/loclikelysubtags.cpp b/icu4c/source/common/loclikelysubtags.cpp
index c18219105..a750bb7b1 100644
--- a/icu4c/source/common/loclikelysubtags.cpp
+++ b/icu4c/source/common/loclikelysubtags.cpp
@@ -564,47 +564,40 @@ LSR LikelySubtags::makeMaximizedLsr(const char *language, const char *script, co
     // Handle pseudolocales like en-XA, ar-XB, fr-PSCRACK.
     // They should match only themselves,
     // not other locales with what looks like the same language and script subtags.
-    char c1;
-    if (region[0] == 'X' && (c1 = region[1]) != 0 && region[2] == 0) {
-        switch (c1) {
-        case 'A':
-            if (returnInputIfUnmatch) {
-                return LSR(language, script, region, LSR::EXPLICIT_LSR);
-            }
-            return LSR(PSEUDO_ACCENTS_PREFIX, language, script, region,
-                       LSR::EXPLICIT_LSR, errorCode);
-        case 'B':
-            if (returnInputIfUnmatch) {
-                return LSR(language, script, region, LSR::EXPLICIT_LSR);
-            }
-            return LSR(PSEUDO_BIDI_PREFIX, language, script, region,
-                       LSR::EXPLICIT_LSR, errorCode);
-        case 'C':
-            if (returnInputIfUnmatch) {
-                return LSR(language, script, region, LSR::EXPLICIT_LSR);
+    if (!returnInputIfUnmatch) {
+        char c1;
+        if (region[0] == 'X' && (c1 = region[1]) != 0 && region[2] == 0) {
+            switch (c1) {
+            case 'A':
+                return LSR(PSEUDO_ACCENTS_PREFIX, language, script, region,
+                           LSR::EXPLICIT_LSR, errorCode);
+            case 'B':
+                return LSR(PSEUDO_BIDI_PREFIX, language, script, region,
+                           LSR::EXPLICIT_LSR, errorCode);
+            case 'C':
+                return LSR(PSEUDO_CRACKED_PREFIX, language, script, region,
+                           LSR::EXPLICIT_LSR, errorCode);
+            default:  // normal locale
+                break;
             }
-            return LSR(PSEUDO_CRACKED_PREFIX, language, script, region,
-                       LSR::EXPLICIT_LSR, errorCode);
-        default:  // normal locale
-            break;
         }
-    }
 
-    if (variant[0] == 'P' && variant[1] == 'S') {
-        int32_t lsrFlags = *region == 0 ?
-            LSR::EXPLICIT_LANGUAGE | LSR::EXPLICIT_SCRIPT : LSR::EXPLICIT_LSR;
-        if (uprv_strcmp(variant, "PSACCENT") == 0) {
-            return LSR(PSEUDO_ACCENTS_PREFIX, language, script,
-                       *region == 0 ? "XA" : region, lsrFlags, errorCode);
-        } else if (uprv_strcmp(variant, "PSBIDI") == 0) {
-            return LSR(PSEUDO_BIDI_PREFIX, language, script,
-                       *region == 0 ? "XB" : region, lsrFlags, errorCode);
-        } else if (uprv_strcmp(variant, "PSCRACK") == 0) {
-            return LSR(PSEUDO_CRACKED_PREFIX, language, script,
-                       *region == 0 ? "XC" : region, lsrFlags, errorCode);
+        if (variant[0] == 'P' && variant[1] == 'S') {
+            int32_t lsrFlags = *region == 0 ?
+                LSR::EXPLICIT_LANGUAGE | LSR::EXPLICIT_SCRIPT : LSR::EXPLICIT_LSR;
+            if (uprv_strcmp(variant, "PSACCENT") == 0) {
+                return LSR(PSEUDO_ACCENTS_PREFIX, language, script,
+                           *region == 0 ? "XA" : region, lsrFlags, errorCode);
+            } else if (uprv_strcmp(variant, "PSBIDI") == 0) {
+                return LSR(PSEUDO_BIDI_PREFIX, language, script,
+                           *region == 0 ? "XB" : region, lsrFlags, errorCode);
+            } else if (uprv_strcmp(variant, "PSCRACK") == 0) {
+                return LSR(PSEUDO_CRACKED_PREFIX, language, script,
+                           *region == 0 ? "XC" : region, lsrFlags, errorCode);
+            }
+            // else normal locale
         }
-        // else normal locale
-    }
+    } // end of if (!returnInputIfUnmatch)
 
     language = getCanonical(languageAliases, language);
     // (We have no script mappings.)
diff --git a/icu4c/source/test/cintltst/cloctst.c b/icu4c/source/test/cintltst/cloctst.c
index 04efd5f37..5815b14f2 100644
--- a/icu4c/source/test/cintltst/cloctst.c
+++ b/icu4c/source/test/cintltst/cloctst.c
@@ -3920,17 +3920,17 @@ const char* const basic_maximize_data[][2] = {
     "zh_Hani",
     "zh_Hani_CN" // If change, please also update common/unicode/uloc.h
   }, {
-    // ICU-22545
+    // ICU-22545 & ICU-22742
     "en_XA",
-    "en_XA"
+    "en_Latn_XA"
   }, {
-    // ICU-22545
-    "en_XB",
-    "en_XB"
+    // ICU-22545 & ICU-22742
+    "ar_XB",
+    "ar_Arab_XB"
   }, {
-    // ICU-22545
-    "en_XC",
-    "en_XC"
+    // ICU-22545 & ICU-22742
+    "ru_XC",
+    "ru_Cyrl_XC"
   }
 };
 
diff --git a/icu4c/source/test/intltest/loctest.cpp b/icu4c/source/test/intltest/loctest.cpp
index f39fb1ad5..dc0947bfd 100644
--- a/icu4c/source/test/intltest/loctest.cpp
+++ b/icu4c/source/test/intltest/loctest.cpp
@@ -233,6 +233,7 @@ void LocaleTest::runIndexedTest( int32_t index, UBool exec, const char* &name, c
 #endif
     TESTCASE_AUTO(TestSetIsBogus);
     TESTCASE_AUTO(TestParallelAPIValues);
+    TESTCASE_AUTO(TestPseudoLocales);
     TESTCASE_AUTO(TestAddLikelySubtags);
     TESTCASE_AUTO(TestMinimizeSubtags);
     TESTCASE_AUTO(TestAddLikelyAndMinimizeSubtags);
@@ -1741,6 +1742,119 @@ LocaleTest::TestSetIsBogus() {
 }
 
 
+void LocaleTest::TestPseudoLocales() {
+    // input locale tag, expected locale tag
+    static const struct {
+        const char* const input;
+        const char* const expected;
+    } test_cases[] = {
+        // language + region, en
+        { "en-XA", "en-Latn-XA" },
+        { "en-XB", "en-Latn-XB" },
+        { "en-XC", "en-Latn-XC" },
+
+        // language + region, ar
+        { "ar-XA", "ar-Arab-XA" },
+        { "ar-XB", "ar-Arab-XB" },
+        { "ar-XC", "ar-Arab-XC" },
+
+        // language + region, something other than en, ar
+        { "ru-XA", "ru-Cyrl-XA" },
+        { "el-XB", "el-Grek-XB" },
+
+        // undefined language - region
+        { "und-XA", "en-Latn-XA" },
+        { "und-XB", "en-Latn-XB" },
+        { "und-XC", "en-Latn-XC" },
+
+        // language + script + region
+        { "und-Latn-XA", "en-Latn-XA" },
+        { "und-Latn-XB", "en-Latn-XB" },
+        { "und-Latn-XC", "en-Latn-XC" },
+        { "und-Arab-XA", "ar-Arab-XA" },
+        { "und-Arab-XB", "ar-Arab-XB" },
+        { "und-Arab-XC", "ar-Arab-XC" },
+        { "und-Cyrl-XA", "ru-Cyrl-XA" },
+        { "und-Grek-XB", "el-Grek-XB" },
+
+        // Make sure the script is not damaged, when correct
+        { "ru-Cyrl-XA", "ru-Cyrl-XA" },
+        { "el-Grek-XB", "el-Grek-XB" },
+
+        // Make sure the script is not damaged, even if it is wrong
+        { "ru-Grek-XA", "ru-Grek-XA" },
+        { "el-Cyrl-XB", "el-Cyrl-XB" },
+
+        // PS Variants
+        { "en-XA-PSACCENT", "en-Latn-XA-psaccent" },
+        { "en-XA-PSBIDI", "en-Latn-XA-psbidi" },
+        { "en-XA-PSCRACK", "en-Latn-XA-pscrack" },
+        { "ar-XB-PSACCENT", "ar-Arab-XB-psaccent" },
+        { "ar-XB-PSBIDI", "ar-Arab-XB-psbidi" },
+        { "ar-XB-PSCRACK", "ar-Arab-XB-pscrack" },
+        { "en-XC-PSACCENT", "en-Latn-XC-psaccent" },
+        { "en-XC-PSBIDI", "en-Latn-XC-psbidi" },
+        { "en-XC-PSCRACK", "en-Latn-XC-pscrack" },
+
+        { "en-US-PSACCENT", "en-Latn-US-psaccent" },
+        { "en-US-PSBIDI", "en-Latn-US-psbidi" },
+        { "en-US-PSCRACK", "en-Latn-US-pscrack" },
+        { "ar-EG-PSACCENT", "ar-Arab-EG-psaccent" },
+        { "ar-EG-PSBIDI", "ar-Arab-EG-psbidi" },
+        { "ar-EG-PSCRACK", "ar-Arab-EG-pscrack" },
+
+        { "en-PSACCENT", "en-Latn-US-psaccent" },
+        { "en-PSBIDI", "en-Latn-US-psbidi" },
+        { "en-PSCRACK", "en-Latn-US-pscrack" },
+        { "ar-PSACCENT", "ar-Arab-EG-psaccent" },
+        { "ar-PSBIDI", "ar-Arab-EG-psbidi" },
+        { "ar-PSCRACK", "ar-Arab-EG-pscrack" },
+
+        { "und-US-PSACCENT", "en-Latn-US-psaccent" },
+        { "und-US-PSBIDI", "en-Latn-US-psbidi" },
+        { "und-US-PSCRACK", "en-Latn-US-pscrack" },
+        { "und-EG-PSACCENT", "ar-Arab-EG-psaccent" },
+        { "und-EG-PSBIDI", "ar-Arab-EG-psbidi" },
+        { "und-EG-PSCRACK", "ar-Arab-EG-pscrack" },
+
+        { "und-PSACCENT", "en-Latn-US-psaccent" },
+        { "und-PSBIDI", "en-Latn-US-psbidi" },
+        { "und-PSCRACK", "en-Latn-US-pscrack" },
+        { "und-PSACCENT", "en-Latn-US-psaccent" },
+        { "und-PSBIDI", "en-Latn-US-psbidi" },
+        { "und-PSCRACK", "en-Latn-US-pscrack" },
+    };
+
+    std::string extensions("-u-nu-Deva-hc-h23-fw-mon-mu-celsius-x-somethin-more");
+
+    IcuTestErrorCode status(*this, "TestPseudoLocales()");
+    for (const auto& item : test_cases) {
+        const char* const inputTag = item.input;
+        const char* const expectedTag = item.expected;
+        Locale result = Locale::forLanguageTag(inputTag, status);
+        result.addLikelySubtags(status);
+        status.errIfFailureAndReset("\"%s\"", inputTag);
+        Locale expected = Locale::forLanguageTag(expectedTag, status);
+        status.errIfFailureAndReset("\"%s\"", expectedTag);
+        assertEquals(inputTag, expected.getName(), result.getName());
+
+        // Test extension
+        std::string extendedTag(inputTag);
+        extendedTag.append(extensions);
+
+        result = Locale::forLanguageTag(extendedTag, status);
+        result.addLikelySubtags(status);
+        status.errIfFailureAndReset(extendedTag.c_str());
+
+        std::string expectedExtendedTag(expectedTag);
+        expectedExtendedTag.append(extensions);
+
+        expected = Locale::forLanguageTag(expectedExtendedTag, status);
+        status.errIfFailureAndReset(expectedExtendedTag.c_str());
+        assertEquals(extendedTag.c_str(), expected.getName(), result.getName());
+    }
+}
+
 void
 LocaleTest::TestAddLikelySubtags() {
     IcuTestErrorCode status(*this, "TestAddLikelySubtags()");
@@ -3974,20 +4088,45 @@ LocaleTest::TestAddLikelyAndMinimizeSubtags() {
             "zh_Hani_CN", // If change, please also update common/unicode/locid.h
             "zh_Hani"
         }, {
-            // ICU-22545
-            "en_XA",
+            // ICU-22545 & ICU-22742
             "en_XA",
+            "en_Latn_XA",
             "en_XA",
         }, {
-            // ICU-22545
-            "en_XB",
-            "en_XB",
-            "en_XB",
+            // ICU-22545 & ICU-22742
+            "ar_XB",
+            "ar_Arab_XB",
+            "ar_XB",
+        }, {
+            // ICU-22545 & ICU-22742
+            "ru_XC",
+            "ru_Cyrl_XC",
+            "ru_XC",
+        }, {
+            // ICU-22742
+            "en_PSACCENT",
+            "en_Latn_US_PSACCENT",
+            "en__PSACCENT"
+        }, {
+            "ar_PSBIDI",
+            "ar_Arab_EG_PSBIDI",
+            "ar__PSBIDI"
+        }, {
+            "ru_PSCRACK",
+            "ru_Cyrl_RU_PSCRACK",
+            "ru__PSCRACK"
+        }, {
+            "ar_PSACCENT",
+            "ar_Arab_EG_PSACCENT",
+            "ar__PSACCENT"
+        }, {
+            "ru_PSBIDI",
+            "ru_Cyrl_RU_PSBIDI",
+            "ru__PSBIDI"
         }, {
-            // ICU-22545
-            "en_XC",
-            "en_XC",
-            "en_XC",
+            "en_PSCRACK",
+            "en_Latn_US_PSCRACK",
+            "en__PSCRACK"
         }
     };
 
diff --git a/icu4c/source/test/intltest/loctest.h b/icu4c/source/test/intltest/loctest.h
index cb79b456d..b3410242e 100644
--- a/icu4c/source/test/intltest/loctest.h
+++ b/icu4c/source/test/intltest/loctest.h
@@ -129,6 +129,7 @@ public:
     void TestKnownCanonicalizedListCorrect();
     void TestConstructorAcceptsBCP47();
 
+    void TestPseudoLocales();
     void TestAddLikelySubtags();
     void TestMinimizeSubtags();
     void TestAddLikelyAndMinimizeSubtags();
diff --git a/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/util/ULocaleTest.java b/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/util/ULocaleTest.java
index 39b981370..3361782ec 100644
--- a/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/util/ULocaleTest.java
+++ b/icu4j/main/common_tests/src/test/java/com/ibm/icu/dev/test/util/ULocaleTest.java
@@ -1972,17 +1972,36 @@ public class ULocaleTest extends CoreTestFmwk {
                     "zh_Hani",
                     "zh_Hani_CN" // If change, please also update ULocale.java
                 }, {
-                    // ICU-22545
-                    "en_XA",
+                    // ICU-22545 & ICU-22742
                     "en_XA",
+                    "en_Latn_XA",
+                }, {
+                    // ICU-22545 & ICU-22742
+                    "ar_XB",
+                    "ar_Arab_XB",
+                }, {
+                    // ICU-22545 & ICU-22742
+                    "ru_XC",
+                    "ru_Cyrl_XC",
+                }, {
+                    // ICU-22742
+                    "en_PSACCENT",
+                    "en_Latn_US_PSACCENT",
+                }, {
+                    "ar_PSBIDI",
+                    "ar_Arab_EG_PSBIDI",
+                }, {
+                    "ru_PSCRACK",
+                    "ru_Cyrl_RU_PSCRACK",
                 }, {
-                    // ICU-22545
-                    "en_XB",
-                    "en_XB",
+                    "ar_PSACCENT",
+                    "ar_Arab_EG_PSACCENT",
                 }, {
-                    // ICU-22545
-                    "en_XC",
-                    "en_XC",
+                    "ru_PSBIDI",
+                    "ru_Cyrl_RU_PSBIDI",
+                }, {
+                    "en_PSCRACK",
+                    "en_Latn_US_PSCRACK",
                 }
         };
 
@@ -5592,6 +5611,103 @@ public class ULocaleTest extends CoreTestFmwk {
         return tests;
     }
 
+    // ICU-22742, test addLikelySubtags with pseudo-locales
+    @Test
+    public void TestPseudoLocales() {
+        // input locale tag, expected locale tag
+        String[][] testCases = new String[][] {
+                // language + region, en
+                { "en-XA", "en-Latn-XA" },
+                { "en-XB", "en-Latn-XB" },
+                { "en-XC", "en-Latn-XC" },
+
+                // language + region, ar
+                { "ar-XA", "ar-Arab-XA" },
+                { "ar-XB", "ar-Arab-XB" },
+                { "ar-XC", "ar-Arab-XC" },
+
+                // language + region, something other than en, ar
+                { "ru-XA", "ru-Cyrl-XA" },
+                { "el-XB", "el-Grek-XB" },
+
+                // undefined language - region
+                { "und-XA", "en-Latn-XA" },
+                { "und-XB", "en-Latn-XB" },
+                { "und-XC", "en-Latn-XC" },
+
+                // language + script + region
+                { "und-Latn-XA", "en-Latn-XA" },
+                { "und-Latn-XB", "en-Latn-XB" },
+                { "und-Latn-XC", "en-Latn-XC" },
+                { "und-Arab-XA", "ar-Arab-XA" },
+                { "und-Arab-XB", "ar-Arab-XB" },
+                { "und-Arab-XC", "ar-Arab-XC" },
+                { "und-Cyrl-XA", "ru-Cyrl-XA" },
+                { "und-Grek-XB", "el-Grek-XB" },
+
+                // Make sure the script is not damaged, when correct
+                { "ru-Cyrl-XA", "ru-Cyrl-XA" },
+                { "el-Grek-XB", "el-Grek-XB" },
+
+                // Make sure the script is not damaged, even if it is wrong
+                { "ru-Grek-XA", "ru-Grek-XA" },
+                { "el-Cyrl-XB", "el-Cyrl-XB" },
+
+                // PS Variants
+                { "en-XA-PSACCENT", "en-Latn-XA-psaccent" },
+                { "en-XA-PSBIDI", "en-Latn-XA-psbidi" },
+                { "en-XA-PSCRACK", "en-Latn-XA-pscrack" },
+                { "ar-XB-PSACCENT", "ar-Arab-XB-psaccent" },
+                { "ar-XB-PSBIDI", "ar-Arab-XB-psbidi" },
+                { "ar-XB-PSCRACK", "ar-Arab-XB-pscrack" },
+                { "en-XC-PSACCENT", "en-Latn-XC-psaccent" },
+                { "en-XC-PSBIDI", "en-Latn-XC-psbidi" },
+                { "en-XC-PSCRACK", "en-Latn-XC-pscrack" },
+
+                { "en-US-PSACCENT", "en-Latn-US-psaccent" },
+                { "en-US-PSBIDI", "en-Latn-US-psbidi" },
+                { "en-US-PSCRACK", "en-Latn-US-pscrack" },
+                { "ar-EG-PSACCENT", "ar-Arab-EG-psaccent" },
+                { "ar-EG-PSBIDI", "ar-Arab-EG-psbidi" },
+                { "ar-EG-PSCRACK", "ar-Arab-EG-pscrack" },
+
+                { "en-PSACCENT", "en-Latn-US-psaccent" },
+                { "en-PSBIDI", "en-Latn-US-psbidi" },
+                { "en-PSCRACK", "en-Latn-US-pscrack" },
+                { "ar-PSACCENT", "ar-Arab-EG-psaccent" },
+                { "ar-PSBIDI", "ar-Arab-EG-psbidi" },
+                { "ar-PSCRACK", "ar-Arab-EG-pscrack" },
+
+                { "und-US-PSACCENT", "en-Latn-US-psaccent" },
+                { "und-US-PSBIDI", "en-Latn-US-psbidi" },
+                { "und-US-PSCRACK", "en-Latn-US-pscrack" },
+                { "und-EG-PSACCENT", "ar-Arab-EG-psaccent" },
+                { "und-EG-PSBIDI", "ar-Arab-EG-psbidi" },
+                { "und-EG-PSCRACK", "ar-Arab-EG-pscrack" },
+
+                { "und-PSACCENT", "en-Latn-US-psaccent" },
+                { "und-PSBIDI", "en-Latn-US-psbidi" },
+                { "und-PSCRACK", "en-Latn-US-pscrack" },
+                { "und-PSACCENT", "en-Latn-US-psaccent" },
+                { "und-PSBIDI", "en-Latn-US-psbidi" },
+                { "und-PSCRACK", "en-Latn-US-pscrack" },
+        };
+        String extensions = "-u-nu-Deva-hc-h23-fw-mon-mu-celsius-x-something-more";
+
+        for (String[] testCase : testCases) {
+            String inputTag = testCase[0];
+            String expectedTag = testCase[1];
+            ULocale result = ULocale.addLikelySubtags(ULocale.forLanguageTag(inputTag));
+            ULocale expected = ULocale.forLanguageTag(expectedTag);
+            assertEquals("pseudo-locales(" + inputTag + ")", expected, result);
+
+            // Make sure this also works with extensions. Kind of hacky...
+            result = ULocale.addLikelySubtags(ULocale.forLanguageTag(inputTag + extensions));
+            expected = ULocale.forLanguageTag(expectedTag + extensions);
+            assertEquals("pseudo-locales(" + inputTag + ")", expected, result);
+        }
+    }
+
     @Test
     @Parameters(method = "readLikelySubtagsTestCases")
     public void likelySubtagsDataDriven(TestCase test) {
diff --git a/icu4j/main/core/src/main/java/com/ibm/icu/impl/locale/LikelySubtags.java b/icu4j/main/core/src/main/java/com/ibm/icu/impl/locale/LikelySubtags.java
index 6d5a35379..2a42c60c4 100644
--- a/icu4j/main/core/src/main/java/com/ibm/icu/impl/locale/LikelySubtags.java
+++ b/icu4j/main/core/src/main/java/com/ibm/icu/impl/locale/LikelySubtags.java
@@ -213,49 +213,42 @@ public final class LikelySubtags {
         // Handle pseudolocales like en-XA, ar-XB, fr-PSCRACK.
         // They should match only themselves,
         // not other locales with what looks like the same language and script subtags.
-        if (region.length() == 2 && region.charAt(0) == 'X') {
-            switch (region.charAt(1)) {
-            case 'A':
-                if (returnInputIfUnmatch) {
-                    return new LSR(language, script, region, LSR.EXPLICIT_LSR);
-                }
-                return new LSR(PSEUDO_ACCENTS_PREFIX + language,
-                        PSEUDO_ACCENTS_PREFIX + script, region, LSR.EXPLICIT_LSR);
-            case 'B':
-                if (returnInputIfUnmatch) {
-                    return new LSR(language, script, region, LSR.EXPLICIT_LSR);
-                }
-                return new LSR(PSEUDO_BIDI_PREFIX + language,
-                        PSEUDO_BIDI_PREFIX + script, region, LSR.EXPLICIT_LSR);
-            case 'C':
-                if (returnInputIfUnmatch) {
-                    return new LSR(language, script, region, LSR.EXPLICIT_LSR);
+        if (!returnInputIfUnmatch) {
+            if (region.length() == 2 && region.charAt(0) == 'X') {
+                switch (region.charAt(1)) {
+                case 'A':
+                    return new LSR(PSEUDO_ACCENTS_PREFIX + language,
+                            PSEUDO_ACCENTS_PREFIX + script, region, LSR.EXPLICIT_LSR);
+                case 'B':
+                    return new LSR(PSEUDO_BIDI_PREFIX + language,
+                            PSEUDO_BIDI_PREFIX + script, region, LSR.EXPLICIT_LSR);
+                case 'C':
+                    return new LSR(PSEUDO_CRACKED_PREFIX + language,
+                            PSEUDO_CRACKED_PREFIX + script, region, LSR.EXPLICIT_LSR);
+                default:  // normal locale
+                    break;
                 }
-                return new LSR(PSEUDO_CRACKED_PREFIX + language,
-                        PSEUDO_CRACKED_PREFIX + script, region, LSR.EXPLICIT_LSR);
-            default:  // normal locale
-                break;
             }
-        }
 
-        if (variant.startsWith("PS")) {
-            int lsrFlags = region.isEmpty() ?
-                    LSR.EXPLICIT_LANGUAGE | LSR.EXPLICIT_SCRIPT : LSR.EXPLICIT_LSR;
-            switch (variant) {
-            case "PSACCENT":
-                return new LSR(PSEUDO_ACCENTS_PREFIX + language,
-                        PSEUDO_ACCENTS_PREFIX + script,
-                        region.isEmpty() ? "XA" : region, lsrFlags);
-            case "PSBIDI":
-                return new LSR(PSEUDO_BIDI_PREFIX + language,
-                        PSEUDO_BIDI_PREFIX + script,
-                        region.isEmpty() ? "XB" : region, lsrFlags);
-            case "PSCRACK":
-                return new LSR(PSEUDO_CRACKED_PREFIX + language,
-                        PSEUDO_CRACKED_PREFIX + script,
-                        region.isEmpty() ? "XC" : region, lsrFlags);
-            default:  // normal locale
-                break;
+            if (variant.startsWith("PS")) {
+                int lsrFlags = region.isEmpty() ?
+                            LSR.EXPLICIT_LANGUAGE | LSR.EXPLICIT_SCRIPT : LSR.EXPLICIT_LSR;
+                switch (variant) {
+                case "PSACCENT":
+                    return new LSR(PSEUDO_ACCENTS_PREFIX + language,
+                            PSEUDO_ACCENTS_PREFIX + script,
+                            region.isEmpty() ? "XA" : region, lsrFlags);
+                case "PSBIDI":
+                    return new LSR(PSEUDO_BIDI_PREFIX + language,
+                            PSEUDO_BIDI_PREFIX + script,
+                            region.isEmpty() ? "XB" : region, lsrFlags);
+                case "PSCRACK":
+                    return new LSR(PSEUDO_CRACKED_PREFIX + language,
+                            PSEUDO_CRACKED_PREFIX + script,
+                            region.isEmpty() ? "XC" : region, lsrFlags);
+                default:  // normal locale
+                    break;
+                }
             }
         }