8257964: Broken Calendar#getMinimalDaysInFirstWeek with java.locale.providers=HOST

Reviewed-by: joehw

src/java.base/windows/classes/sun/util/locale/provider/HostLocaleProviderAdapterImpl.java

@@ -75,7 +75,7 @@ public class HostLocaleProviderAdapterImpl {
 
     // CalendarData value types
     private static final int CD_FIRSTDAYOFWEEK = 0;
-    private static final int CD_MINIMALDAYSINFIRSTWEEK = 1;
+    private static final int CD_FIRSTWEEKOFYEAR = 1;
 
     // Currency/Locale display name types
     private static final int DN_CURRENCY_NAME   = 0;
@@ -366,7 +366,15 @@ public class HostLocaleProviderAdapterImpl {
 
             @Override
             public int getMinimalDaysInFirstWeek(Locale locale) {
-                return 0;
+                int firstWeek = getCalendarDataValue(
+                        removeExtensions(locale).toLanguageTag(),
+                        CD_FIRSTWEEKOFYEAR);
+                // Interpret the value from Windows LOCALE_IFIRSTWEEKOFYEAR setting
+                return switch (firstWeek) {
+                    case 1 -> 7; // First full week following 1/1 is the first week of the year.
+                    case 2 -> 4; // First week containing at least four days is the first week of the year.
+                    default -> 1; // First week can be a single day, if 1/1 falls on the last day of the week.
+                };
             }
         };
     }

src/java.base/windows/native/libjava/HostLocaleProviderAdapter_md.c

@@ -647,6 +647,11 @@ JNIEXPORT jint JNICALL Java_sun_util_locale_provider_HostLocaleProviderAdapterIm
             LOCALE_IFIRSTDAYOFWEEK | LOCALE_RETURN_NUMBER,
             (LPWSTR)&num, sizeof(num));
         break;
+    case sun_util_locale_provider_HostLocaleProviderAdapterImpl_CD_FIRSTWEEKOFYEAR:
+        got = getLocaleInfoWrapper(langtag,
+            LOCALE_IFIRSTWEEKOFYEAR | LOCALE_RETURN_NUMBER,
+            (LPWSTR)&num, sizeof(num));
+        break;
     }
 
     (*env)->ReleaseStringChars(env, jlangtag, langtag);

test/jdk/java/util/Locale/LocaleProviders.java

@@ -27,6 +27,7 @@ import java.time.ZoneId;
 import java.time.ZonedDateTime;
 import java.time.format.DateTimeFormatter;
 import java.time.format.FormatStyle;
+import java.time.temporal.WeekFields;
 import java.util.*;
 import java.util.logging.Level;
 import java.util.logging.LogRecord;
@@ -110,6 +111,10 @@ public class LocaleProviders {
                 bug8248695Test();
                 break;
 
+            case "bug8257964Test":
+                bug8257964Test();
+                break;
+
             default:
                 throw new RuntimeException("Test method '"+methodName+"' not found.");
         }
@@ -433,4 +438,34 @@ public class LocaleProviders {
             System.out.println(dtf.format(zdt));
         }
     }
+
+    // Run only if the platform locale is en-GB
+    static void bug8257964Test() {
+        var defLoc = Locale.getDefault(Locale.Category.FORMAT);
+        var type = LocaleProviderAdapter.getAdapter(CalendarNameProvider.class, Locale.UK)
+                .getAdapterType();
+        if (defLoc.equals(Locale.UK) &&
+                type == LocaleProviderAdapter.Type.HOST &&
+                (IS_WINDOWS || IS_MAC)) {
+            Calendar instance = Calendar.getInstance(Locale.UK);
+            int result = instance.getMinimalDaysInFirstWeek();
+            if (result != 4) {
+                throw new RuntimeException("MinimalDaysInFirstWeek for Locale.UK is incorrect. " +
+                        "returned: " + result);
+            }
+
+            LocalDate date = LocalDate.of(2020,12,31);
+            result = date.get(WeekFields.of(Locale.UK).weekOfWeekBasedYear());
+            if (result != 53) {
+                throw new RuntimeException("weekNumber is incorrect. " +
+                        "returned: " + result);
+            }
+            System.out.println("bug8257964Test succeeded.");
+        } else {
+            System.out.println("Test ignored. Either :-\n" +
+                    "Default format locale is not Locale.UK: " + defLoc + ", or\n" +
+                    "OS is neither macOS/Windows, or\n" +
+                    "provider is not HOST: " + type);
+        }
+    }
 }

test/jdk/java/util/Locale/LocaleProvidersRun.java

@@ -26,7 +26,7 @@
  * @bug 6336885 7196799 7197573 7198834 8000245 8000615 8001440 8008577
  *      8010666 8013086 8013233 8013903 8015960 8028771 8054482 8062006
  *      8150432 8215913 8220227 8228465 8232871 8232860 8236495 8245241
- *      8246721 8248695
+ *      8246721 8248695 8257964
  * @summary tests for "java.locale.providers" system property
  * @library /test/lib
  * @build LocaleProviders
@@ -172,6 +172,9 @@ public class LocaleProvidersRun {
 
         //testing 8248695 fix.
         testRun("HOST", "bug8248695Test", "", "", "");
+
+        //testing 8257964 fix. (macOS/Windows only)
+        testRun("HOST", "bug8257964Test", "", "", "");
     }
 
     private static void testRun(String prefList, String methodName,