Cherry-pick: ICU-22378 Fix temperature format ignoring -u-mu-fahrenhe

Upstream commit:
https://github.com/unicode-org/icu/commit/0e4b10b1121a26fe4d1653d740f5a15bad9c48f0
Upstream bug:
https://unicode-org.atlassian.net/browse/ICU-22378

Bug: 280473143
Test: CtsIcuTestCases
(cherry picked from https://android-review.googlesource.com/q/commit:7c77b31dee56dbc69fe9444810d5ba6daf2a2df1)
Merged-In: I44aa63d96f667a2865744e50e4419e2296decb96
Change-Id: I44aa63d96f667a2865744e50e4419e2296decb96

2 files changed, 64 insertions, 1 deletions

diff --git a/icu4j/main/classes/core/src/com/ibm/icu/impl/units/UnitPreferences.java b/icu4j/main/classes/core/src/com/ibm/icu/impl/units/UnitPreferences.java
index 962bcf0a9..39d6b0ac1 100644
--- a/icu4j/main/classes/core/src/com/ibm/icu/impl/units/UnitPreferences.java
+++ b/icu4j/main/classes/core/src/com/ibm/icu/impl/units/UnitPreferences.java
@@ -72,8 +72,13 @@ public class UnitPreferences {
 
     public UnitPreference[] getPreferencesFor(String category, String usage, ULocale locale, UnitsData data) {
         // TODO: remove this condition when all the categories are allowed.
-        if (category.equals("temperature")) {
+        // WARNING: when this is removed please make sure to keep the "fahrenhe" => "fahrenheit" mapping
+        if ("temperature".equals(category)) {
             String localeUnit = locale.getKeywordValue("mu");
+            // The value for -u-mu- is `fahrenhe`, but CLDR and everything else uses `fahrenheit`
+            if ("fahrenhe".equals(localeUnit)) {
+                localeUnit = "fahrenheit";
+            }
             String localeUnitCategory;
             try {
                 localeUnitCategory = localeUnit == null ? null : data.getCategory(MeasureUnitImpl.forIdentifier(localeUnit));
diff --git a/icu4j/main/tests/core/src/com/ibm/icu/dev/test/number/NumberFormatterApiTest.java b/icu4j/main/tests/core/src/com/ibm/icu/dev/test/number/NumberFormatterApiTest.java
index ec9e5462f..e194cf1b0 100644
--- a/icu4j/main/tests/core/src/com/ibm/icu/dev/test/number/NumberFormatterApiTest.java
+++ b/icu4j/main/tests/core/src/com/ibm/icu/dev/test/number/NumberFormatterApiTest.java
@@ -5995,6 +5995,64 @@ public class NumberFormatterApiTest extends TestFmwk {
         }
     }
 
+    @Test
+    public void testIssue22378() {
+        class TestCase {
+            final String localeId;
+            final String expectedFormat;
+
+            TestCase(String localeId, String expectedFormat) {
+                this.localeId = localeId;
+                this.expectedFormat = expectedFormat;
+            }
+        }
+
+        // I checked the results before the fix and everything works the same except
+        // "fr-FR-u-mu-fahrenhe" and "fr_FR@mu=fahrenhe"
+        final TestCase [] testCases = {
+                new TestCase("en-US", "73\u00B0F"),
+                new TestCase("en-US-u-mu-fahrenhe", "73\u00B0F"),
+                // WAI. "fahrenheit" is an invalid -u-mu- value, we get the default for en-US
+                new TestCase("en-US-u-mu-fahrenheit", "73\u00B0F"),
+                new TestCase("en-US-u-mu-celsius", "23\u00B0C"),
+                new TestCase("en-US-u-mu-badvalue", "73\u00B0F"),
+                new TestCase("en_US@mu=fahrenhe", "73\u00B0F"),
+                new TestCase("en_US@mu=fahrenheit", "73\u00B0F"),
+                new TestCase("en_US@mu=celsius", "23\u00B0C"),
+                new TestCase("en_US@mu=badvalue", "73\u00B0F"),
+
+                new TestCase("fr-FR", "23\u202F\u00B0C"),
+                new TestCase("fr-FR-u-mu-fahrenhe", "73\u202F\u00B0F"),
+                // WAI. Celsius because "fahrenheit" is an invalid -u-mu- value, we get the default for fr-FR
+                new TestCase("fr-FR-u-mu-fahrenheit", "23\u202F\u00B0C"),
+                new TestCase("fr-FR-u-mu-celsius", "23\u202F\u00B0C"),
+                new TestCase("fr-FR-u-mu-badvalue", "23\u202F\u00B0C"),
+                new TestCase("fr_FR@mu=fahrenhe", "73\u202F\u00B0F"),
+                new TestCase("fr_FR@mu=fahrenheit", "73\u202F\u00B0F"),
+                new TestCase("fr_FR@mu=celsius", "23\u202F\u00B0C"),
+                new TestCase("fr_FR@mu=badvalue", "23\u202F\u00B0C"),
+        };
+
+        final UnlocalizedNumberFormatter formatter = NumberFormatter.with()
+                .usage("weather")
+                .unit(MeasureUnit.CELSIUS);
+        final double value = 23.0;
+
+        for (TestCase testCase : testCases) {
+            String localeId = testCase.localeId;
+            ULocale locale = localeId.contains("@")
+                    ? new ULocale(localeId)
+                    : ULocale.forLanguageTag(localeId);
+            String actualFormat = formatter.locale(locale).format(value).toString();
+            assertEquals("-u-mu- honored (" + localeId + ")", testCase.expectedFormat, actualFormat);
+        }
+
+        String result = formatter.locale(Locale.US).format(value).getOutputUnit().getIdentifier();
+        assertEquals("Testing default -u-mu- for en-US", MeasureUnit.FAHRENHEIT.getIdentifier(), result);
+        result = formatter.locale(Locale.FRANCE).format(value).getOutputUnit().getIdentifier();
+        assertEquals("Testing default -u-mu- for fr-FR", MeasureUnit.CELSIUS.getIdentifier(), result);
+    }
+
     static void assertFormatDescending(
             String message,
             String skeleton,