[Java.time] Retain prefixed date pattern in formatter (#48703)

JavaDateFormatter should keep the pattern with the prefixed 8 as it will be used for serialisation. The stripped pattern should be used for the enclosed formatters.

closes #48698

modules/ingest-common/src/main/java/org/elasticsearch/ingest/common/DateFormat.java

@@ -82,11 +82,6 @@ enum DateFormat {
 
         @Override
         Function<String, ZonedDateTime> getFunction(String format, ZoneId zoneId, Locale locale) {
-            // support the 6.x BWC compatible way of parsing java 8 dates
-            if (format.startsWith("8")) {
-                format = format.substring(1);
-            }
-
             boolean isUtc = ZoneOffset.UTC.equals(zoneId);
 
             DateFormatter dateFormatter = DateFormatter.forPattern(format)

rest-api-spec/src/main/resources/rest-api-spec/test/search/180_locale_dependent_mapping.yml

@@ -1,8 +1,8 @@
 ---
 "Test Index and Search locale dependent mappings / dates":
   - skip:
-      version: "all"
-      reason: "Awaits fix: https://github.com/elastic/elasticsearch/issues/39981(Previously: JDK9 only supports this with a special sysproperty added in 6.2.0.)"
+      version: " - 6.1.99"
+      reason: JDK9 only supports this with a special sysproperty added in 6.2.0
   - do:
       indices.create:
           index: test_index
@@ -13,7 +13,7 @@
                   properties:
                       date_field:
                           type: date
-                          format: "E, d MMM yyyy HH:mm:ss Z"
+                          format: "8E, d MMM uuuu HH:mm:ss Z"
                           locale: "de"
   - do:
       bulk:

server/src/main/java/org/elasticsearch/common/time/DateFormatter.java

@@ -129,27 +129,28 @@ public interface DateFormatter {
     DateMathParser toDateMathParser();
 
     static DateFormatter forPattern(String input) {
+
         if (Strings.hasLength(input) == false) {
             throw new IllegalArgumentException("No date pattern provided");
         }
 
         // support the 6.x BWC compatible way of parsing java 8 dates
-        if (input.startsWith("8")) {
-            input = input.substring(1);
-        }
-
-        List<String> patterns = splitCombinedPatterns(input);
+        String format = strip8Prefix(input);
+        List<String> patterns = splitCombinedPatterns(format);
         List<DateFormatter> formatters = patterns.stream()
                                                  .map(DateFormatters::forPattern)
                                                  .collect(Collectors.toList());
 
-        if (formatters.size() == 1) {
-            return formatters.get(0);
-        }
-
         return JavaDateFormatter.combined(input, formatters);
     }
 
+    static String strip8Prefix(String input) {
+        if (input.startsWith("8")) {
+            return input.substring(1);
+        }
+        return input;
+    }
+
     static List<String> splitCombinedPatterns(String input) {
         List<String> patterns = new ArrayList<>();
         for (String pattern : Strings.delimitedListToStringArray(input, "||")) {

server/src/main/java/org/elasticsearch/index/mapper/DocumentMapper.java

@@ -339,4 +339,21 @@ public class DocumentMapper implements ToXContentFragment {
     public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
         return mapping.toXContent(builder, params);
     }
+
+    @Override
+    public String toString() {
+        return "DocumentMapper{" +
+            "mapperService=" + mapperService +
+            ", type='" + type + '\'' +
+            ", typeText=" + typeText +
+            ", mappingSource=" + mappingSource +
+            ", mapping=" + mapping +
+            ", documentParser=" + documentParser +
+            ", fieldMappers=" + fieldMappers +
+            ", objectMappers=" + objectMappers +
+            ", hasNestedObjects=" + hasNestedObjects +
+            ", deleteTombstoneMetadataFieldMappers=" + Arrays.toString(deleteTombstoneMetadataFieldMappers) +
+            ", noopTombstoneMetadataFieldMappers=" + Arrays.toString(noopTombstoneMetadataFieldMappers) +
+            '}';
+    }
 }