Do not prefix already prefixed format with 8 (#48139)

It happens when a locale is specified on a mapping that a new
JavaDateFormatter is created with a new mapping and already prefixed
with 8 format is prefixed again. This should change avoids this
behavior.
relates  #47983

Author: pgomulka

server/build.gradle

@@ -150,6 +150,8 @@ check.dependsOn(testScriptDocValuesMissingV7Behaviour)
 unitTest {
   // these are tested explicitly in separate test tasks
   exclude '**/*ScriptDocValuesMissingV7BehaviourTests.class'
+  jvmArg '-Djava.locale.providers=COMPAT'
+
 }
 
 forbiddenPatterns {

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

@@ -76,7 +76,7 @@ class JavaDateFormatter implements DateFormatter {
             throw new IllegalArgumentException("formatters must have the same locale");
         }
         this.printer = printer;
-        this.format = "8" + format;
+        this.format = format.startsWith("8") ? format : "8" + format;
 
         if (parsers.length == 0) {
             this.parsers = Collections.singletonList(printer);

server/src/test/java/org/elasticsearch/action/admin/indices/create/CreateIndexIT.java

@@ -42,6 +42,7 @@
 import org.elasticsearch.test.ESIntegTestCase;
 import org.elasticsearch.test.ESIntegTestCase.ClusterScope;
 import org.elasticsearch.test.ESIntegTestCase.Scope;
+import org.hamcrest.Matchers;
 
 import java.util.HashMap;
 import java.util.List;
@@ -56,8 +57,6 @@
 import static org.hamcrest.Matchers.allOf;
 import static org.hamcrest.Matchers.equalTo;
 import static org.hamcrest.Matchers.greaterThanOrEqualTo;
-import static org.hamcrest.Matchers.hasSize;
-import static org.hamcrest.Matchers.is;
 import static org.hamcrest.Matchers.lessThanOrEqualTo;
 import static org.hamcrest.core.IsNull.notNullValue;
 
@@ -385,21 +384,38 @@ public void testIndexNameInResponse() {
     }
 
     public void testCreateIndexWithJava8Date() throws Exception {
-        String jodaIncompatibleFormat = "8yyyy-MM-dd HH:mm:ssXX";
-        XContentBuilder builder = jsonBuilder().startObject().startObject("properties")
-            .startObject("time")
-            .field("type", "date")
-            .field("format", jodaIncompatibleFormat)
-            .endObject().endObject().endObject();
-
-        CreateIndexRequestBuilder requestBuilder = client().admin().indices().prepareCreate("test");
-        assertAcked(requestBuilder.addMapping("doc", builder).get());
+        BiFunction<XContentBuilder, String, List<Object>> createIndex = (xContentBuilder, propertyToBeReturned) -> {
+            String indexName = "test" + xContentBuilder.hashCode();
+            CreateIndexRequestBuilder requestBuilder = client().admin().indices().prepareCreate(indexName);
+            assertAcked(requestBuilder.addMapping("doc", xContentBuilder).get());
+
+            GetMappingsResponse response = client().admin().indices().prepareGetMappings(indexName).get();
+            List<Object> formats = XContentMapValues.extractRawValues(propertyToBeReturned, response
+                .getMappings()
+                .get(indexName)
+                .get("doc")
+                .getSourceAsMap());
+            return formats;
+        };
 
-        GetMappingsResponse response = client().admin().indices().prepareGetMappings("test").get();
-        List<Object> formats =
-            XContentMapValues.extractRawValues("properties.time.format", response.getMappings().get("test").get("doc").getSourceAsMap());
-        assertThat(formats, hasSize(1));
-        assertThat(formats.get(0), is(jodaIncompatibleFormat));
+        XContentBuilder builder = jsonBuilder().startObject().startObject("properties")
+                                               .startObject("time")
+                                               .field("type", "date")
+                                               .field("format", "8yyyy-MM-dd-MM-dd HH:mm:ssXX")
+                                               .endObject()
+                                               .endObject().endObject();
+
+        assertThat(createIndex.apply(builder, "properties.time.format"), Matchers.contains("8yyyy-MM-dd-MM-dd HH:mm:ssXX"));
+
+
+        builder = jsonBuilder().startObject().startObject("properties")
+                                               .startObject("time")
+                                               .field("type", "date")
+                                               .field("format", "8yyyy-MM-dd-MM-dd HH:mm:ssXX")
+                                               .field("locale", "de")
+                                               .endObject()
+                                               .endObject().endObject();
+        assertThat(createIndex.apply(builder, "properties.time.locale"), Matchers.contains("de"));
     }
 
 }

server/src/test/java/org/elasticsearch/index/mapper/DateFieldMapperTests.java

@@ -270,6 +270,18 @@ public void testFloatEpochFormat() throws IOException {
         assertEquals(epochMillis, pointField.numericValue().longValue());
     }
 
+    public void testChangeLocaleWith8Prefix() throws IOException {
+        String mapping = Strings.toString(XContentFactory.jsonBuilder().startObject().startObject("type")
+                                                         .startObject("properties").startObject("field").field("type", "date")
+                                                         .field("format", "8E, d MMM uuuu HH:mm:ss Z")
+                                                         .field("locale", "de")
+                                                         .endObject().endObject().endObject().endObject());
+
+        DocumentMapper mapper = parser.parse("type", new CompressedXContent(mapping));
+
+        assertEquals(mapping, mapper.mappingSource().toString());
+    }
+
     public void testChangeLocale() throws IOException {
         String mapping = Strings.toString(XContentFactory.jsonBuilder().startObject().startObject("type")
                 .startObject("properties").startObject("field").field("type", "date").field("locale", "fr").endObject().endObject()