a.t.f.DateFormat behaves consistently with j.t.DateFormat in en, en-US locale

DateUtils.formatSameDayTime() test is also updated, because the javadoc
refers to j.t.DateFormat directly. It makes sense to follow
j.t.DateFormat behavior.

The rest of a.t.f.DateUtils is not updated because it's used for
different purposes, e.g. date/time interval, relative date/time, duration, etc.
'\u202f' NNBS character use is acceptable in this case because
it's unlikely being parsed.

Bug: 266731719
Test: atest FrameworksCoreTests:android.text.format
Test: atest CtsTextTestCases:android.text.format
Change-Id: Ib5c916e2b7a66a5faef7bf214be25db88213d91d
diff --git a/core/java/android/text/format/DateFormat.java b/core/java/android/text/format/DateFormat.java
index d48d566..e6dad27 100755
--- a/core/java/android/text/format/DateFormat.java
+++ b/core/java/android/text/format/DateFormat.java
@@ -24,12 +24,12 @@
 import android.content.Context;
 import android.icu.text.DateFormatSymbols;
 import android.icu.text.DateTimePatternGenerator;
+import android.icu.util.ULocale;
 import android.os.Build;
 import android.provider.Settings;
 import android.text.SpannableStringBuilder;
 import android.text.Spanned;
 import android.text.SpannedString;
-import android.text.TextUtils;
 
 import java.text.SimpleDateFormat;
 import java.util.Calendar;
@@ -265,11 +265,13 @@
      * @return a string pattern suitable for use with {@link java.text.SimpleDateFormat}.
      */
     public static String getBestDateTimePattern(Locale locale, String skeleton) {
-        DateTimePatternGenerator dtpg = DateTimePatternGenerator.getInstance(locale);
+        ULocale uLocale = ULocale.forLocale(locale);
+        DateTimePatternGenerator dtpg = DateTimePatternGenerator.getInstance(uLocale);
         boolean allowDuplicateFields = !CompatChanges.isChangeEnabled(
                 DISALLOW_DUPLICATE_FIELD_IN_SKELETON);
-        return dtpg.getBestPattern(skeleton, DateTimePatternGenerator.MATCH_NO_OPTIONS,
+        String pattern = dtpg.getBestPattern(skeleton, DateTimePatternGenerator.MATCH_NO_OPTIONS,
                 allowDuplicateFields);
+        return getCompatibleEnglishPattern(uLocale, pattern);
     }
 
     /**
@@ -303,10 +305,11 @@
      */
     @UnsupportedAppUsage
     public static String getTimeFormatString(Context context, int userHandle) {
-        DateTimePatternGenerator dtpg = DateTimePatternGenerator.getInstance(
-                context.getResources().getConfiguration().locale);
-        return is24HourFormat(context, userHandle) ? dtpg.getBestPattern("Hm")
+        ULocale uLocale = ULocale.forLocale(context.getResources().getConfiguration().locale);
+        DateTimePatternGenerator dtpg = DateTimePatternGenerator.getInstance(uLocale);
+        String pattern = is24HourFormat(context, userHandle) ? dtpg.getBestPattern("Hm")
             : dtpg.getBestPattern("hm");
+        return getCompatibleEnglishPattern(uLocale, pattern);
     }
 
     /**
@@ -713,4 +716,21 @@
     public static DateFormatSymbols getIcuDateFormatSymbols(Locale locale) {
         return new DateFormatSymbols(android.icu.util.GregorianCalendar.class, locale);
     }
+
+    /**
+     * See http://b/266731719. It mirrors the implementation in
+     * {@link libcore.icu.SimpleDateFormatData.DateTimeFormatStringGenerator#postProcessPattern}
+     */
+    private static String getCompatibleEnglishPattern(ULocale locale, String pattern) {
+        if (pattern == null || locale == null || !"en".equals(locale.getLanguage())) {
+            return pattern;
+        }
+
+        String region = locale.getCountry();
+        if (region != null && !region.isEmpty() && !"US".equals(region)) {
+            return pattern;
+        }
+
+        return pattern.replace('\u202f', ' ');
+    }
 }
diff --git a/core/tests/coretests/src/android/text/format/DateFormatTest.java b/core/tests/coretests/src/android/text/format/DateFormatTest.java
index 8459330..212cc44 100644
--- a/core/tests/coretests/src/android/text/format/DateFormatTest.java
+++ b/core/tests/coretests/src/android/text/format/DateFormatTest.java
@@ -156,8 +156,8 @@
     @DisableCompatChanges({DateFormat.DISALLOW_DUPLICATE_FIELD_IN_SKELETON})
     public void testGetBestDateTimePattern_enableDuplicateField() {
         // en-US uses 12-hour format by default.
-        assertEquals("h:mm\u202fa", DateFormat.getBestDateTimePattern(Locale.US, "jmma"));
-        assertEquals("h:mm\u202fa", DateFormat.getBestDateTimePattern(Locale.US, "ahmma"));
+        assertEquals("h:mm a", DateFormat.getBestDateTimePattern(Locale.US, "jmma"));
+        assertEquals("h:mm a", DateFormat.getBestDateTimePattern(Locale.US, "ahmma"));
     }
 
     private static void assertIllegalArgumentException(Locale l, String skeleton) {
diff --git a/core/tests/coretests/src/android/text/format/DateUtilsTest.java b/core/tests/coretests/src/android/text/format/DateUtilsTest.java
index 39ed82ef..381c051 100644
--- a/core/tests/coretests/src/android/text/format/DateUtilsTest.java
+++ b/core/tests/coretests/src/android/text/format/DateUtilsTest.java
@@ -139,16 +139,16 @@
                 fixedTime, java.text.DateFormat.SHORT, java.text.DateFormat.FULL));
 
         final long hourDuration = 2 * 60 * 60 * 1000;
-        assertEquals("5:30:15\u202fAM Greenwich Mean Time", DateUtils.formatSameDayTime(
+        assertEquals("5:30:15 AM Greenwich Mean Time", DateUtils.formatSameDayTime(
                 fixedTime + hourDuration, fixedTime, java.text.DateFormat.FULL,
                 java.text.DateFormat.FULL));
-        assertEquals("5:30:15\u202fAM", DateUtils.formatSameDayTime(fixedTime + hourDuration,
+        assertEquals("5:30:15 AM", DateUtils.formatSameDayTime(fixedTime + hourDuration,
                 fixedTime, java.text.DateFormat.FULL, java.text.DateFormat.DEFAULT));
-        assertEquals("5:30:15\u202fAM GMT", DateUtils.formatSameDayTime(fixedTime + hourDuration,
+        assertEquals("5:30:15 AM GMT", DateUtils.formatSameDayTime(fixedTime + hourDuration,
                 fixedTime, java.text.DateFormat.FULL, java.text.DateFormat.LONG));
-        assertEquals("5:30:15\u202fAM", DateUtils.formatSameDayTime(fixedTime + hourDuration,
+        assertEquals("5:30:15 AM", DateUtils.formatSameDayTime(fixedTime + hourDuration,
                 fixedTime, java.text.DateFormat.FULL, java.text.DateFormat.MEDIUM));
-        assertEquals("5:30\u202fAM", DateUtils.formatSameDayTime(fixedTime + hourDuration,
+        assertEquals("5:30 AM", DateUtils.formatSameDayTime(fixedTime + hourDuration,
                 fixedTime, java.text.DateFormat.FULL, java.text.DateFormat.SHORT));
     }