Ignore null value for range field (#27845) (#28116)

Currently when adding a document with a `null` value for a range field,
the range field mapper raises an error. Instead we should ignore null like 
we do eg. with numbers or geo points.

Closes #27845

core/src/main/java/org/elasticsearch/index/mapper/RangeFieldMapper.java

@@ -357,7 +357,9 @@ public class RangeFieldMapper extends FieldMapper {
         } else {
             XContentParser parser = context.parser();
             final XContentParser.Token start = parser.currentToken();
-            if (start == XContentParser.Token.START_OBJECT) {
+            if (start == XContentParser.Token.VALUE_NULL) {
+                return;
+            } else if (start == XContentParser.Token.START_OBJECT) {
                 RangeFieldType fieldType = fieldType();
                 RangeType rangeType = fieldType.rangeType;
                 String fieldName = null;

core/src/test/java/org/elasticsearch/index/mapper/RangeFieldMapperTests.java

@@ -363,6 +363,15 @@ public class RangeFieldMapperTests extends AbstractNumericFieldMapperTestCase {
                 + InetAddresses.toAddrString(InetAddresses.forString("ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff"));
         }
         assertThat(storedField.stringValue(), containsString(strVal));
+
+        // test null range
+        doc = mapper.parse(SourceToParse.source("test", "type", "1", XContentFactory.jsonBuilder()
+                .startObject()
+                .nullField("field")
+                .endObject()
+                .bytes(),
+            XContentType.JSON));
+        assertNull(doc.rootDoc().get("field"));
     }
 
     public void testNoBounds() throws Exception {

rest-api-spec/src/main/resources/rest-api-spec/test/range/10_basic.yml

@@ -45,6 +45,12 @@ setup:
         id: 3
         body: { "integer_range" : { "gte": 4, "lte": 5 } }
 
+  - do:
+      index:
+        index: test
+        type: doc
+        id: 4
+        body: { "integer_range" : null }
 
   - do:
       indices.refresh: {}
@@ -79,6 +85,12 @@ setup:
 
   - match: { hits.total: 0 }
 
+  - do:
+      search:
+        body: { "query" : { "match_all": {} } }
+
+  - match: { hits.total: 4 }
+
 ---
 "Long range":