From d1581238f41f9844c663445bcd169cbae94c4f37 Mon Sep 17 00:00:00 2001
From: Rich Gillam <62772518+richgillam@users.noreply.github.com>
Date: Wed, 21 Oct 2020 17:14:55 -0700
Subject: [PATCH] ICU-21342 Made sure adjustFieldWidth() got called on the
 duplicated hour pattern used for UCAL_AM_PM in 24-hour patterns.

---
 icu4c/source/i18n/dtitvfmt.cpp                            | 6 +++++-
 icu4c/source/test/intltest/dtifmtts.cpp                   | 6 ++++++
 .../core/src/com/ibm/icu/text/DateIntervalFormat.java     | 8 ++++++++
 .../ibm/icu/dev/test/format/DateIntervalFormatTest.java   | 6 ++++++
 4 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/icu4c/source/i18n/dtitvfmt.cpp b/icu4c/source/i18n/dtitvfmt.cpp
index 2433a80b017..8dd2bcdca4b 100644
--- a/icu4c/source/i18n/dtitvfmt.cpp
+++ b/icu4c/source/i18n/dtitvfmt.cpp
@@ -1422,7 +1422,11 @@ DateIntervalFormat::setIntervalPattern(UCalendarDateFields field,
         if ( field == UCAL_AM_PM ) {
             fInfo->getIntervalPattern(*bestSkeleton, UCAL_HOUR, pattern,status);
             if ( !pattern.isEmpty() ) {
-                setIntervalPattern(field, pattern);
+                UBool suppressDayPeriodField = fSkeleton.indexOf(CAP_J) != -1;
+                UnicodeString adjustIntervalPattern;
+                adjustFieldWidth(*skeleton, *bestSkeleton, pattern, differenceInfo,
+                                 suppressDayPeriodField, adjustIntervalPattern);
+                setIntervalPattern(field, adjustIntervalPattern);
             }
             return false;
         }
diff --git a/icu4c/source/test/intltest/dtifmtts.cpp b/icu4c/source/test/intltest/dtifmtts.cpp
index a1b1152face..878eca1291e 100644
--- a/icu4c/source/test/intltest/dtifmtts.cpp
+++ b/icu4c/source/test/intltest/dtifmtts.cpp
@@ -1160,6 +1160,12 @@ void DateIntervalFormatTest::testHourMetacharacters() {
         "hi_IN", "CE 2010 09 27 00:00:00", "CE 2010 09 27 01:00:00", "hB", "\\u0930\\u093E\\u0924 12\\u20131",
         "hi_IN", "CE 2010 09 27 10:00:00", "CE 2010 09 27 13:00:00", "CC", "\\u0938\\u0941\\u092C\\u0939 10 \\u2013 \\u0926\\u094B\\u092A\\u0939\\u0930 1",
         "hi_IN", "CE 2010 09 27 00:00:00", "CE 2010 09 27 01:00:00", "CC", "\\u0930\\u093E\\u0924 12\\u20131",
+
+         // regression test for ICU-21342
+         "en_GB", "CE 2010 09 27 00:00:00", "CE 2010 09 27 10:00:00", "kk", "24\\u201310",
+         "en_GB", "CE 2010 09 27 00:00:00", "CE 2010 09 27 11:00:00", "kk", "24\\u201311",
+         "en_GB", "CE 2010 09 27 00:00:00", "CE 2010 09 27 12:00:00", "kk", "24\\u201312",
+         "en_GB", "CE 2010 09 27 00:00:00", "CE 2010 09 27 13:00:00", "kk", "24\\u201313",
     };
     expect(DATA, UPRV_LENGTHOF(DATA));
 }
diff --git a/icu4j/main/classes/core/src/com/ibm/icu/text/DateIntervalFormat.java b/icu4j/main/classes/core/src/com/ibm/icu/text/DateIntervalFormat.java
index 9befd1edecb..2b4e8599514 100644
--- a/icu4j/main/classes/core/src/com/ibm/icu/text/DateIntervalFormat.java
+++ b/icu4j/main/classes/core/src/com/ibm/icu/text/DateIntervalFormat.java
@@ -1982,6 +1982,14 @@ public class DateIntervalFormat extends UFormat {
                  pattern = fInfo.getIntervalPattern(bestSkeleton,
                                                          Calendar.HOUR);
                  if ( pattern != null ) {
+                    boolean suppressDayPeriodField = fSkeleton.indexOf('J') != -1;
+                    String part1 = adjustFieldWidth(skeleton, bestSkeleton,
+                                       pattern.getFirstPart(), differenceInfo, suppressDayPeriodField);
+                    String part2 = adjustFieldWidth(skeleton, bestSkeleton,
+                                       pattern.getSecondPart(), differenceInfo, suppressDayPeriodField);
+                    pattern =  new PatternInfo(part1, part2,
+                                               pattern.firstDateInPtnIsLaterDate());
+                                               
                       // share
                       intervalPatterns.put(DateIntervalInfo.
                           CALENDAR_FIELD_TO_PATTERN_LETTER[field],
diff --git a/icu4j/main/tests/core/src/com/ibm/icu/dev/test/format/DateIntervalFormatTest.java b/icu4j/main/tests/core/src/com/ibm/icu/dev/test/format/DateIntervalFormatTest.java
index 24577564bbb..d9d9522c275 100644
--- a/icu4j/main/tests/core/src/com/ibm/icu/dev/test/format/DateIntervalFormatTest.java
+++ b/icu4j/main/tests/core/src/com/ibm/icu/dev/test/format/DateIntervalFormatTest.java
@@ -805,6 +805,12 @@ public class DateIntervalFormatTest extends TestFmwk {
         "hi_IN", "CE 2010 09 27 00:00:00", "CE 2010 09 27 01:00:00", "hB", "\\u0930\\u093E\\u0924 12\\u20131",
         "hi_IN", "CE 2010 09 27 10:00:00", "CE 2010 09 27 13:00:00", "CC", "\\u0938\\u0941\\u092C\\u0939 10 \\u2013 \\u0926\\u094B\\u092A\\u0939\\u0930 1",
         "hi_IN", "CE 2010 09 27 00:00:00", "CE 2010 09 27 01:00:00", "CC", "\\u0930\\u093E\\u0924 12\\u20131",
+
+         // regression test for ICU-21342
+         "en_GB", "CE 2010 09 27 00:00:00", "CE 2010 09 27 10:00:00", "kk", "24\\u201310",
+         "en_GB", "CE 2010 09 27 00:00:00", "CE 2010 09 27 11:00:00", "kk", "24\\u201311",
+         "en_GB", "CE 2010 09 27 00:00:00", "CE 2010 09 27 12:00:00", "kk", "24\\u201312",
+         "en_GB", "CE 2010 09 27 00:00:00", "CE 2010 09 27 13:00:00", "kk", "24\\u201313",
         };
         expect(DATA, DATA.length);
     }