Remove the 'array value parser' marker interface. (#57571) (#57623)

This PR replaces the marker interface with the method
FieldMapper#parsesArrayValue. I find this cleaner and it will help with the
fields retrieval work (#55363).

The refactor also ensures that only field mappers can declare they parse array
values. Previously other types like ObjectMapper could implement the marker
interface and be passed array values, which doesn't make sense.

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

@@ -244,6 +244,11 @@ protected void parseCreateField(ParseContext context, List<IndexableField> field
         throw new UnsupportedOperationException("Parsing is implemented in parse(), this method should NEVER be called");
     }
 
+    @Override
+    public final boolean parsesArrayValue() {
+        return true;
+    }
+
     @Override
     public void doXContentBody(XContentBuilder builder, boolean includeDefaults, Params params) throws IOException {
         super.doXContentBody(builder, includeDefaults, params);

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

@@ -85,7 +85,7 @@
  *  This field can also be extended to add search criteria to suggestions
  *  for query-time filtering and boosting (see {@link ContextMappings}
  */
-public class CompletionFieldMapper extends FieldMapper implements ArrayValueMapperParser {
+public class CompletionFieldMapper extends FieldMapper {
     public static final String CONTENT_TYPE = "completion";
 
     /**
@@ -441,6 +441,11 @@ public CompletionFieldType fieldType() {
         return (CompletionFieldType) super.fieldType();
     }
 
+    @Override
+    public boolean parsesArrayValue() {
+        return true;
+    }
+
     /**
      * Parses and indexes inputs
      *

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

@@ -541,7 +541,7 @@ private static void parseArray(ParseContext context, ObjectMapper parentMapper,
             // There is a concrete mapper for this field already. Need to check if the mapper
             // expects an array, if so we pass the context straight to the mapper and if not
             // we serialize the array components
-            if (mapper instanceof ArrayValueMapperParser) {
+            if (parsesArrayValue(mapper)) {
                 parseObjectOrField(context, mapper);
             } else {
                 parseNonDynamicArray(context, parentMapper, lastFieldName, arrayFieldName);
@@ -562,7 +562,7 @@ private static void parseArray(ParseContext context, ObjectMapper parentMapper,
                     Mapper.BuilderContext builderContext = new Mapper.BuilderContext(context.indexSettings().getSettings(), context.path());
                     mapper = builder.build(builderContext);
                     assert mapper != null;
-                    if (mapper instanceof ArrayValueMapperParser) {
+                    if (parsesArrayValue(mapper)) {
                         context.addDynamicMapper(mapper);
                         context.path().add(arrayFieldName);
                         parseObjectOrField(context, mapper);
@@ -581,6 +581,10 @@ private static void parseArray(ParseContext context, ObjectMapper parentMapper,
         }
     }
 
+    private static boolean parsesArrayValue(Mapper mapper) {
+        return mapper instanceof FieldMapper && ((FieldMapper) mapper).parsesArrayValue();
+    }
+
     private static void parseNonDynamicArray(ParseContext context, ObjectMapper mapper,
                                              final String lastFieldName, String arrayFieldName) throws IOException {
         XContentParser parser = context.parser();

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

@@ -275,6 +275,16 @@ public CopyTo copyTo() {
         return copyTo;
     }
 
+    /**
+     * Whether this mapper can handle an array value during document parsing. If true,
+     * when an array is encountered during parsing, the document parser will pass the
+     * whole array to the mapper. If false, the array is split into individual values
+     * and each value is passed to the mapper for parsing.
+     */
+    public boolean parsesArrayValue() {
+        return false;
+    }
+
     /**
      * Parse the field value using the provided {@link ParseContext}.
      */

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

@@ -54,7 +54,7 @@
  *
  * Uses lucene 6 LatLonPoint encoding
  */
-public class GeoPointFieldMapper extends AbstractGeometryFieldMapper implements ArrayValueMapperParser {
+public class GeoPointFieldMapper extends AbstractGeometryFieldMapper {
     public static final String CONTENT_TYPE = "geo_point";
 
     public static class Names extends AbstractGeometryFieldMapper.Names {

x-pack/plugin/spatial/src/main/java/org/elasticsearch/xpack/spatial/index/mapper/PointFieldMapper.java

@@ -18,7 +18,6 @@
 import org.elasticsearch.common.xcontent.XContentBuilder;
 import org.elasticsearch.common.xcontent.XContentParser;
 import org.elasticsearch.index.mapper.AbstractGeometryFieldMapper;
-import org.elasticsearch.index.mapper.ArrayValueMapperParser;
 import org.elasticsearch.index.mapper.MappedFieldType;
 import org.elasticsearch.index.mapper.Mapper;
 import org.elasticsearch.index.mapper.MapperParsingException;
@@ -40,7 +39,7 @@
  *
  * Uses lucene 8 XYPoint encoding
  */
-public class PointFieldMapper extends AbstractGeometryFieldMapper implements ArrayValueMapperParser {
+public class PointFieldMapper extends AbstractGeometryFieldMapper {
     public static final String CONTENT_TYPE = "point";
 
     public static class Names extends AbstractGeometryFieldMapper.Names {

x-pack/plugin/vectors/src/main/java/org/elasticsearch/xpack/vectors/mapper/DenseVectorFieldMapper.java

@@ -19,7 +19,6 @@
 import org.elasticsearch.common.xcontent.XContentParser.Token;
 import org.elasticsearch.common.xcontent.support.XContentMapValues;
 import org.elasticsearch.index.fielddata.IndexFieldData;
-import org.elasticsearch.index.mapper.ArrayValueMapperParser;
 import org.elasticsearch.index.mapper.FieldMapper;
 import org.elasticsearch.index.mapper.MappedFieldType;
 import org.elasticsearch.index.mapper.Mapper;
@@ -42,7 +41,7 @@
 /**
  * A {@link FieldMapper} for indexing a dense vector of floats.
  */
-public class DenseVectorFieldMapper extends FieldMapper implements ArrayValueMapperParser {
+public class DenseVectorFieldMapper extends FieldMapper {
 
     public static final String CONTENT_TYPE = "dense_vector";
     public static short MAX_DIMS_COUNT = 2048; //maximum allowed number of dimensions
@@ -180,6 +179,11 @@ public DenseVectorFieldType fieldType() {
         return (DenseVectorFieldType) super.fieldType();
     }
 
+    @Override
+    public boolean parsesArrayValue() {
+        return true;
+    }
+
     @Override
     public void parse(ParseContext context) throws IOException {
         if (context.externalValueSet()) {