Use ignore source in match only text

Author: Kubik42

modules/mapper-extras/src/main/java/org/elasticsearch/index/mapper/extras/MatchOnlyTextFieldMapper.java

@@ -13,7 +13,6 @@
 import org.apache.lucene.analysis.TokenStream;
 import org.apache.lucene.document.Field;
 import org.apache.lucene.document.FieldType;
-import org.apache.lucene.document.StoredField;
 import org.apache.lucene.index.IndexOptions;
 import org.apache.lucene.index.LeafReaderContext;
 import org.apache.lucene.index.Term;
@@ -683,12 +682,11 @@ protected void parseCreateField(DocumentParserContext context) throws IOExceptio
             // if the delegate can't support synthetic source for the given value, then store a copy of said value so
             // that synthetic source can load it
             if (fieldType().textFieldType.canUseSyntheticSourceDelegateForSyntheticSource(value.string()) == false) {
-                final String fieldName = fieldType().syntheticSourceFallbackFieldName();
                 if (storedFieldInBinaryFormat) {
                     final var bytesRef = new BytesRef(utfBytes.bytes(), utfBytes.offset(), utfBytes.length());
-                    context.doc().add(new StoredField(fieldName, bytesRef));
+                    context.storeFieldForSyntheticSource(fullPath(), leafName(), bytesRef, context.doc());
                 } else {
-                    context.doc().add(new StoredField(fieldName, value.string()));
+                    context.storeFieldForSyntheticSource(fullPath(), leafName(), context.encodeFlattenedToken(), context.doc());
                 }
             }
         }
@@ -706,7 +704,13 @@ public MatchOnlyTextFieldType fieldType() {
 
     @Override
     protected SyntheticSourceSupport syntheticSourceSupport() {
-        return new SyntheticSourceSupport.Native(() -> syntheticFieldLoader(fullPath(), leafName()));
+        var kwd = TextFieldMapper.SyntheticSourceHelper.getKeywordFieldMapperForSyntheticSource(this);
+        if (kwd != null) {
+            // merge the two field loaders into one
+            return new SyntheticSourceSupport.Native(() -> kwd.syntheticFieldLoader(fullPath(), leafName()));
+        }
+
+        return super.syntheticSourceSupport();
     }
 
     private SourceLoader.SyntheticFieldLoader syntheticFieldLoader(String fullFieldName, String leafFieldName) {

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

@@ -391,7 +391,7 @@ public final DocumentParserContext addIgnoredFieldFromContext(IgnoredSourceField
      * For instance: { "a.b": "b", "a.c": "c" } => { "a": { "b": "b" }, "a": { "c": "c" } }
      * This can happen when storing parts of document source that are not indexed (e.g. disabled objects).
      */
-    BytesRef encodeFlattenedToken() throws IOException {
+    public BytesRef encodeFlattenedToken() throws IOException {
         boolean old = path().isWithinLeafObject();
         path().setWithinLeafObject(true);
         BytesRef encoded = XContentDataHelper.encodeToken(parser());