Refactor build params for FieldMapper, adding SourceKeepMode (#112455)

* Refactor build params for FieldMapper

* more mappers and tests

* more mappers

* more mappers

* spotless

* spotless

* stored by default

* Revert "stored by default"

This reverts commit bbd247d64b.

* restore storeIgnored

* sync

* list valid values for SourceKeepMode

* small refactoring

* spotless

modules/legacy-geo/src/main/java/org/elasticsearch/legacygeo/mapper/LegacyGeoShapeFieldMapper.java

@@ -352,7 +352,7 @@ public class LegacyGeoShapeFieldMapper extends AbstractShapeGeometryFieldMapper<
         public LegacyGeoShapeFieldMapper build(MapperBuilderContext context) {
             LegacyGeoShapeParser parser = new LegacyGeoShapeParser();
             GeoShapeFieldType ft = buildFieldType(parser, context);
-            return new LegacyGeoShapeFieldMapper(leafName(), ft, multiFieldsBuilder.build(this, context), copyTo, parser, this);
+            return new LegacyGeoShapeFieldMapper(leafName(), ft, builderParams(this, context), parser, this);
         }
     }
 
@@ -537,20 +537,18 @@ public class LegacyGeoShapeFieldMapper extends AbstractShapeGeometryFieldMapper<
     public LegacyGeoShapeFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         LegacyGeoShapeParser parser,
         Builder builder
     ) {
         super(
             simpleName,
             mappedFieldType,
+            builderParams,
             builder.ignoreMalformed.get(),
             builder.coerce.get(),
             builder.ignoreZValue.get(),
             builder.orientation.get(),
-            multiFields,
-            copyTo,
             parser
         );
         this.indexCreatedVersion = builder.indexCreatedVersion;

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

@@ -139,13 +139,11 @@ public class MatchOnlyTextFieldMapper extends FieldMapper {
         @Override
         public MatchOnlyTextFieldMapper build(MapperBuilderContext context) {
             MatchOnlyTextFieldType tft = buildFieldType(context);
-            MultiFields multiFields = multiFieldsBuilder.build(this, context);
             return new MatchOnlyTextFieldMapper(
                 leafName(),
                 Defaults.FIELD_TYPE,
                 tft,
-                multiFields,
+                builderParams(this, context),
-                copyTo,
                 context.isSourceSynthetic(),
                 this
             );
@@ -382,12 +380,11 @@ public class MatchOnlyTextFieldMapper extends FieldMapper {
         String simpleName,
         FieldType fieldType,
         MatchOnlyTextFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         boolean storeSource,
         Builder builder
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, false, null);
+        super(simpleName, mappedFieldType, builderParams);
         assert mappedFieldType.getTextSearchInfo().isTokenized();
         assert mappedFieldType.hasDocValues() == false;
         this.fieldType = freezeAndDeduplicateFieldType(fieldType);
@@ -442,7 +439,7 @@ public class MatchOnlyTextFieldMapper extends FieldMapper {
 
     @Override
     public SourceLoader.SyntheticFieldLoader syntheticFieldLoader() {
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

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

@@ -98,8 +98,7 @@ public class RankFeatureFieldMapper extends FieldMapper {
                     positiveScoreImpact.getValue(),
                     nullValue.getValue()
                 ),
-                multiFieldsBuilder.build(this, context),
+                builderParams(this, context),
-                copyTo,
                 positiveScoreImpact.getValue(),
                 nullValue.getValue()
             );
@@ -172,12 +171,11 @@ public class RankFeatureFieldMapper extends FieldMapper {
     private RankFeatureFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         boolean positiveScoreImpact,
         Float nullValue
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, false, null);
+        super(simpleName, mappedFieldType, builderParams);
         this.positiveScoreImpact = positiveScoreImpact;
         this.nullValue = nullValue;
     }

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

@@ -66,8 +66,7 @@ public class RankFeaturesFieldMapper extends FieldMapper {
             return new RankFeaturesFieldMapper(
                 leafName(),
                 new RankFeaturesFieldType(context.buildFullName(leafName()), meta.getValue(), positiveScoreImpact.getValue()),
-                multiFieldsBuilder.build(this, context),
+                builderParams(this, context),
-                copyTo,
                 positiveScoreImpact.getValue()
             );
         }
@@ -122,11 +121,10 @@ public class RankFeaturesFieldMapper extends FieldMapper {
     private RankFeaturesFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         boolean positiveScoreImpact
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, false, null);
+        super(simpleName, mappedFieldType, builderParams);
         this.positiveScoreImpact = positiveScoreImpact;
     }
 

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

@@ -197,14 +197,7 @@ public class ScaledFloatFieldMapper extends FieldMapper {
                 metric.getValue(),
                 indexMode
             );
-            return new ScaledFloatFieldMapper(
+            return new ScaledFloatFieldMapper(leafName(), type, builderParams(this, context), context.isSourceSynthetic(), this);
-                leafName(),
-                type,
-                multiFieldsBuilder.build(this, context),
-                copyTo,
-                context.isSourceSynthetic(),
-                this
-            );
         }
     }
 
@@ -470,12 +463,11 @@ public class ScaledFloatFieldMapper extends FieldMapper {
     private ScaledFloatFieldMapper(
         String simpleName,
         ScaledFloatFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         boolean isSourceSynthetic,
         Builder builder
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo);
+        super(simpleName, mappedFieldType, builderParams);
         this.isSourceSynthetic = isSourceSynthetic;
         this.indexed = builder.indexed.getValue();
         this.hasDocValues = builder.hasDocValues.getValue();
@@ -728,7 +720,7 @@ public class ScaledFloatFieldMapper extends FieldMapper {
                     + "] doesn't support synthetic source because it doesn't have doc values"
             );
         }
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

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

@@ -262,11 +262,10 @@ public class SearchAsYouTypeFieldMapper extends FieldMapper {
             return new SearchAsYouTypeFieldMapper(
                 leafName(),
                 ft,
-                copyTo,
+                builderParams(this, context),
                 indexAnalyzers,
                 prefixFieldMapper,
                 shingleFieldMappers,
-                multiFieldsBuilder.build(this, context),
                 this
             );
         }
@@ -498,7 +497,7 @@ public class SearchAsYouTypeFieldMapper extends FieldMapper {
         final FieldType fieldType;
 
         PrefixFieldMapper(FieldType fieldType, PrefixFieldType mappedFieldType) {
-            super(mappedFieldType.name(), mappedFieldType, MultiFields.empty(), CopyTo.empty());
+            super(mappedFieldType.name(), mappedFieldType, BuilderParams.empty());
             this.fieldType = Mapper.freezeAndDeduplicateFieldType(fieldType);
         }
 
@@ -537,7 +536,7 @@ public class SearchAsYouTypeFieldMapper extends FieldMapper {
         private final FieldType fieldType;
 
         ShingleFieldMapper(FieldType fieldType, ShingleFieldType mappedFieldtype) {
-            super(mappedFieldtype.name(), mappedFieldtype, MultiFields.empty(), CopyTo.empty());
+            super(mappedFieldtype.name(), mappedFieldtype, BuilderParams.empty());
             this.fieldType = freezeAndDeduplicateFieldType(fieldType);
         }
 
@@ -672,14 +671,13 @@ public class SearchAsYouTypeFieldMapper extends FieldMapper {
     public SearchAsYouTypeFieldMapper(
         String simpleName,
         SearchAsYouTypeFieldType mappedFieldType,
-        CopyTo copyTo,
+        BuilderParams builderParams,
         Map<String, NamedAnalyzer> indexAnalyzers,
         PrefixFieldMapper prefixField,
         ShingleFieldMapper[] shingleFields,
-        MultiFields multiFields,
         Builder builder
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, false, null);
+        super(simpleName, mappedFieldType, builderParams);
         this.prefixField = prefixField;
         this.shingleFields = shingleFields;
         this.maxShingleSize = builder.maxShingleSize.getValue();

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

@@ -87,7 +87,7 @@ public class TokenCountFieldMapper extends FieldMapper {
                 nullValue.getValue(),
                 meta.getValue()
             );
-            return new TokenCountFieldMapper(leafName(), ft, multiFieldsBuilder.build(this, context), copyTo, this);
+            return new TokenCountFieldMapper(leafName(), ft, builderParams(this, context), this);
         }
     }
 
@@ -135,14 +135,8 @@ public class TokenCountFieldMapper extends FieldMapper {
     private final boolean enablePositionIncrements;
     private final Integer nullValue;
 
-    protected TokenCountFieldMapper(
+    protected TokenCountFieldMapper(String simpleName, MappedFieldType defaultFieldType, BuilderParams builderParams, Builder builder) {
-        String simpleName,
+        super(simpleName, defaultFieldType, builderParams);
-        MappedFieldType defaultFieldType,
-        MultiFields multiFields,
-        CopyTo copyTo,
-        Builder builder
-    ) {
-        super(simpleName, defaultFieldType, multiFields, copyTo);
         this.analyzer = builder.analyzer.getValue();
         this.enablePositionIncrements = builder.enablePositionIncrements.getValue();
         this.nullValue = builder.nullValue.getValue();

modules/parent-join/src/main/java/org/elasticsearch/join/mapper/ParentIdFieldMapper.java

@@ -88,7 +88,7 @@ public final class ParentIdFieldMapper extends FieldMapper {
     }
 
     protected ParentIdFieldMapper(String name, boolean eagerGlobalOrdinals) {
-        super(name, new ParentIdFieldType(name, eagerGlobalOrdinals), MultiFields.empty(), CopyTo.empty(), false, null);
+        super(name, new ParentIdFieldType(name, eagerGlobalOrdinals), BuilderParams.empty());
     }
 
     @Override

modules/parent-join/src/main/java/org/elasticsearch/join/mapper/ParentJoinFieldMapper.java

@@ -210,7 +210,7 @@ public final class ParentJoinFieldMapper extends FieldMapper {
         boolean eagerGlobalOrdinals,
         List<Relations> relations
     ) {
-        super(simpleName, mappedFieldType, MultiFields.empty(), CopyTo.empty(), false, null);
+        super(simpleName, mappedFieldType, BuilderParams.empty());
         this.parentIdFields = parentIdFields;
         this.eagerGlobalOrdinals = eagerGlobalOrdinals;
         this.relations = relations;

modules/percolator/src/main/java/org/elasticsearch/percolator/PercolatorFieldMapper.java

@@ -137,8 +137,6 @@ public class PercolatorFieldMapper extends FieldMapper {
         @Override
         public PercolatorFieldMapper build(MapperBuilderContext context) {
             PercolatorFieldType fieldType = new PercolatorFieldType(context.buildFullName(leafName()), meta.getValue());
-            // TODO should percolator even allow multifields?
-            MultiFields multiFields = multiFieldsBuilder.build(this, context);
             context = context.createChildContext(leafName(), null);
             KeywordFieldMapper extractedTermsField = createExtractQueryFieldBuilder(
                 EXTRACTED_TERMS_FIELD_NAME,
@@ -165,8 +163,7 @@ public class PercolatorFieldMapper extends FieldMapper {
             return new PercolatorFieldMapper(
                 leafName(),
                 fieldType,
-                multiFields,
+                builderParams(this, context),
-                copyTo,
                 searchExecutionContext,
                 extractedTermsField,
                 extractionResultField,
@@ -375,8 +372,7 @@ public class PercolatorFieldMapper extends FieldMapper {
     PercolatorFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         Supplier<SearchExecutionContext> searchExecutionContext,
         KeywordFieldMapper queryTermsField,
         KeywordFieldMapper extractionResultField,
@@ -387,7 +383,7 @@ public class PercolatorFieldMapper extends FieldMapper {
         IndexVersion indexCreatedVersion,
         Supplier<TransportVersion> clusterTransportVersion
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo);
+        super(simpleName, mappedFieldType, builderParams);
         this.searchExecutionContext = searchExecutionContext;
         this.queryTermsField = queryTermsField;
         this.extractionResultField = extractionResultField;

plugins/analysis-icu/src/main/java/org/elasticsearch/plugin/analysis/icu/ICUCollationKeywordFieldMapper.java

@@ -336,15 +336,7 @@ public class ICUCollationKeywordFieldMapper extends FieldMapper {
                 ignoreAbove.getValue(),
                 meta.getValue()
             );
-            return new ICUCollationKeywordFieldMapper(
+            return new ICUCollationKeywordFieldMapper(leafName(), buildFieldType(), ft, builderParams(this, context), collator, this);
-                leafName(),
-                buildFieldType(),
-                ft,
-                multiFieldsBuilder.build(this, context),
-                copyTo,
-                collator,
-                this
-            );
         }
     }
 
@@ -474,12 +466,11 @@ public class ICUCollationKeywordFieldMapper extends FieldMapper {
         String simpleName,
         FieldType fieldType,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         Collator collator,
         Builder builder
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, false, null);
+        super(simpleName, mappedFieldType, builderParams);
         assert collator.isFrozen();
         this.fieldType = freezeAndDeduplicateFieldType(fieldType);
         this.params = builder.collatorParams();

plugins/mapper-annotated-text/src/main/java/org/elasticsearch/index/mapper/annotatedtext/AnnotatedTextFieldMapper.java

@@ -150,7 +150,6 @@ public class AnnotatedTextFieldMapper extends FieldMapper {
 
         @Override
         public AnnotatedTextFieldMapper build(MapperBuilderContext context) {
-            MultiFields multiFields = multiFieldsBuilder.build(this, context);
             FieldType fieldType = TextParams.buildFieldType(() -> true, store, indexOptions, norms, termVectors);
             if (fieldType.indexOptions() == IndexOptions.NONE) {
                 throw new IllegalArgumentException("[" + CONTENT_TYPE + "] fields must be indexed");
@@ -162,12 +161,12 @@ public class AnnotatedTextFieldMapper extends FieldMapper {
                     );
                 }
             }
+            BuilderParams builderParams = builderParams(this, context);
             return new AnnotatedTextFieldMapper(
                 leafName(),
                 fieldType,
-                buildFieldType(fieldType, context, multiFields),
+                buildFieldType(fieldType, context, builderParams.multiFields()),
-                multiFields,
+                builderParams,
-                copyTo,
                 this
             );
         }
@@ -523,11 +522,10 @@ public class AnnotatedTextFieldMapper extends FieldMapper {
         String simpleName,
         FieldType fieldType,
         AnnotatedTextFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         Builder builder
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo);
+        super(simpleName, mappedFieldType, builderParams);
         assert fieldType.tokenized();
         this.fieldType = freezeAndDeduplicateFieldType(fieldType);
         this.builder = builder;
@@ -578,7 +576,7 @@ public class AnnotatedTextFieldMapper extends FieldMapper {
 
     @Override
     public SourceLoader.SyntheticFieldLoader syntheticFieldLoader() {
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

plugins/mapper-murmur3/src/main/java/org/elasticsearch/index/mapper/murmur3/Murmur3FieldMapper.java

@@ -57,8 +57,7 @@ public class Murmur3FieldMapper extends FieldMapper {
             return new Murmur3FieldMapper(
                 leafName(),
                 new Murmur3FieldType(context.buildFullName(leafName()), stored.getValue(), meta.getValue()),
-                multiFieldsBuilder.build(this, context),
+                builderParams(this, context)
-                copyTo
             );
         }
     }
@@ -94,8 +93,8 @@ public class Murmur3FieldMapper extends FieldMapper {
         }
     }
 
-    protected Murmur3FieldMapper(String simpleName, MappedFieldType mappedFieldType, MultiFields multiFields, CopyTo copyTo) {
+    protected Murmur3FieldMapper(String simpleName, MappedFieldType mappedFieldType, BuilderParams builderParams) {
-        super(simpleName, mappedFieldType, multiFields, copyTo);
+        super(simpleName, mappedFieldType, builderParams);
     }
 
     @Override

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

@@ -201,32 +201,17 @@ public abstract class AbstractGeometryFieldMapper<T> extends FieldMapper {
     protected AbstractGeometryFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
+        BuilderParams builderParams,
         Explicit<Boolean> ignoreMalformed,
         Explicit<Boolean> ignoreZValue,
-        MultiFields multiFields,
-        CopyTo copyTo,
         Parser<T> parser
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, false, null);
+        super(simpleName, mappedFieldType, builderParams);
         this.ignoreMalformed = ignoreMalformed;
         this.ignoreZValue = ignoreZValue;
         this.parser = parser;
     }
 
-    protected AbstractGeometryFieldMapper(
-        String simpleName,
-        MappedFieldType mappedFieldType,
-        MultiFields multiFields,
-        CopyTo copyTo,
-        Parser<T> parser,
-        OnScriptError onScriptError
-    ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, true, onScriptError);
-        this.ignoreMalformed = Explicit.EXPLICIT_FALSE;
-        this.ignoreZValue = Explicit.EXPLICIT_FALSE;
-        this.parser = parser;
-    }
-
     @Override
     @SuppressWarnings("unchecked")
     public AbstractGeometryFieldType<T> fieldType() {
@@ -252,7 +237,7 @@ public abstract class AbstractGeometryFieldMapper<T> extends FieldMapper {
 
     @Override
     public final void parse(DocumentParserContext context) throws IOException {
-        if (hasScript) {
+        if (builderParams.hasScript()) {
             throw new DocumentParsingException(
                 context.parser().getTokenLocation(),
                 "failed to parse field [" + fieldType().name() + "] of type + " + contentType() + "]",

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

@@ -40,29 +40,16 @@ public abstract class AbstractPointGeometryFieldMapper<T> extends AbstractGeomet
     protected AbstractPointGeometryFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
         Explicit<Boolean> ignoreMalformed,
         Explicit<Boolean> ignoreZValue,
         T nullValue,
-        CopyTo copyTo,
         Parser<T> parser
     ) {
-        super(simpleName, mappedFieldType, ignoreMalformed, ignoreZValue, multiFields, copyTo, parser);
+        super(simpleName, mappedFieldType, builderParams, ignoreMalformed, ignoreZValue, parser);
         this.nullValue = nullValue;
     }
 
-    protected AbstractPointGeometryFieldMapper(
-        String simpleName,
-        MappedFieldType mappedFieldType,
-        MultiFields multiFields,
-        CopyTo copyTo,
-        Parser<T> parser,
-        OnScriptError onScriptError
-    ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, parser, onScriptError);
-        this.nullValue = null;
-    }
-
     public T getNullValue() {
         return nullValue;
     }

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

@@ -244,7 +244,7 @@ public abstract class AbstractScriptFieldType<LeafFactory> extends MappedFieldTy
         ).setSerializerCheck((id, ic, v) -> ic);
 
         private final FieldMapper.Parameter<OnScriptError> onScriptError = FieldMapper.Parameter.onScriptErrorParam(
-            m -> m.onScriptError,
+            m -> m.builderParams.onScriptError(),
             script
         );
 

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

@@ -76,30 +76,14 @@ public abstract class AbstractShapeGeometryFieldMapper<T> extends AbstractGeomet
     protected AbstractShapeGeometryFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
+        BuilderParams builderParams,
         Explicit<Boolean> ignoreMalformed,
         Explicit<Boolean> coerce,
         Explicit<Boolean> ignoreZValue,
         Explicit<Orientation> orientation,
-        MultiFields multiFields,
-        CopyTo copyTo,
         Parser<T> parser
     ) {
-        super(simpleName, mappedFieldType, ignoreMalformed, ignoreZValue, multiFields, copyTo, parser);
+        super(simpleName, mappedFieldType, builderParams, ignoreMalformed, ignoreZValue, parser);
-        this.coerce = coerce;
-        this.orientation = orientation;
-    }
-
-    protected AbstractShapeGeometryFieldMapper(
-        String simpleName,
-        MappedFieldType mappedFieldType,
-        MultiFields multiFields,
-        Explicit<Boolean> coerce,
-        Explicit<Orientation> orientation,
-        CopyTo copyTo,
-        Parser<T> parser,
-        OnScriptError onScriptError
-    ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, parser, onScriptError);
         this.coerce = coerce;
         this.orientation = orientation;
     }

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

@@ -72,8 +72,7 @@ public class BinaryFieldMapper extends FieldMapper {
             return new BinaryFieldMapper(
                 leafName(),
                 new BinaryFieldType(context.buildFullName(leafName()), stored.getValue(), hasDocValues.getValue(), meta.getValue()),
-                multiFieldsBuilder.build(this, context),
+                builderParams(this, context),
-                copyTo,
                 this
             );
         }
@@ -142,14 +141,8 @@ public class BinaryFieldMapper extends FieldMapper {
     private final boolean hasDocValues;
     private final boolean isSyntheticSourceEnabledViaIndexMode;
 
-    protected BinaryFieldMapper(
+    protected BinaryFieldMapper(String simpleName, MappedFieldType mappedFieldType, BuilderParams builderParams, Builder builder) {
-        String simpleName,
+        super(simpleName, mappedFieldType, builderParams);
-        MappedFieldType mappedFieldType,
-        MultiFields multiFields,
-        CopyTo copyTo,
-        Builder builder
-    ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo);
         this.stored = builder.stored.getValue();
         this.hasDocValues = builder.hasDocValues.getValue();
         this.isSyntheticSourceEnabledViaIndexMode = builder.isSyntheticSourceEnabledViaIndexMode;
@@ -207,7 +200,7 @@ public class BinaryFieldMapper extends FieldMapper {
 
     @Override
     public SourceLoader.SyntheticFieldLoader syntheticFieldLoader() {
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

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

@@ -89,7 +89,10 @@ public class BooleanFieldMapper extends FieldMapper {
         ).acceptsNull();
 
         private final Parameter<Script> script = Parameter.scriptParam(m -> toType(m).script);
-        private final Parameter<OnScriptError> onScriptError = Parameter.onScriptErrorParam(m -> toType(m).onScriptError, script);
+        private final Parameter<OnScriptError> onScriptErrorParam = Parameter.onScriptErrorParam(
+            m -> toType(m).builderParams.onScriptError(),
+            script
+        );
 
         private final Parameter<Map<String, String>> meta = Parameter.metaParam();
 
@@ -133,7 +136,16 @@ public class BooleanFieldMapper extends FieldMapper {
 
         @Override
         protected Parameter<?>[] getParameters() {
-            return new Parameter<?>[] { meta, docValues, indexed, nullValue, stored, script, onScriptError, ignoreMalformed, dimension };
+            return new Parameter<?>[] {
+                meta,
+                docValues,
+                indexed,
+                nullValue,
+                stored,
+                script,
+                onScriptErrorParam,
+                ignoreMalformed,
+                dimension };
         }
 
         @Override
@@ -151,14 +163,9 @@ public class BooleanFieldMapper extends FieldMapper {
                 meta.getValue(),
                 dimension.getValue()
             );
-            return new BooleanFieldMapper(
+            hasScript = script.get() != null;
-                leafName(),
+            onScriptError = onScriptErrorParam.getValue();
-                ft,
+            return new BooleanFieldMapper(leafName(), ft, builderParams(this, context), context.isSourceSynthetic(), this);
-                multiFieldsBuilder.build(this, context),
-                copyTo,
-                context.isSourceSynthetic(),
-                this
-            );
         }
 
         private FieldValues<Boolean> scriptValues() {
@@ -427,12 +434,11 @@ public class BooleanFieldMapper extends FieldMapper {
     protected BooleanFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         boolean storeMalformedFields,
         Builder builder
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, builder.script.get() != null, builder.onScriptError.getValue());
+        super(simpleName, mappedFieldType, builderParams);
         this.nullValue = builder.nullValue.getValue();
         this.stored = builder.stored.getValue();
         this.indexed = builder.indexed.getValue();
@@ -561,7 +567,7 @@ public class BooleanFieldMapper extends FieldMapper {
                     + "] doesn't support synthetic source because it doesn't have doc values"
             );
         }
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

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

@@ -207,7 +207,7 @@ public class CompletionFieldMapper extends FieldMapper {
 
             CompletionFieldType ft = new CompletionFieldType(context.buildFullName(leafName()), completionAnalyzer, meta.getValue());
             ft.setContextMappings(contexts.getValue());
-            return new CompletionFieldMapper(leafName(), ft, multiFieldsBuilder.build(this, context), copyTo, this);
+            return new CompletionFieldMapper(leafName(), ft, builderParams(this, context), this);
         }
 
         private void checkCompletionContextsLimit() {
@@ -346,14 +346,8 @@ public class CompletionFieldMapper extends FieldMapper {
 
     private final NamedAnalyzer indexAnalyzer;
 
-    public CompletionFieldMapper(
+    public CompletionFieldMapper(String simpleName, MappedFieldType mappedFieldType, BuilderParams builderParams, Builder builder) {
-        String simpleName,
+        super(simpleName, mappedFieldType, builderParams);
-        MappedFieldType mappedFieldType,
-        MultiFields multiFields,
-        CopyTo copyTo,
-        Builder builder
-    ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo);
         this.builder = builder;
         this.maxInputLength = builder.maxInputLength.getValue();
         this.indexAnalyzer = builder.buildAnalyzer();
@@ -443,7 +437,7 @@ public class CompletionFieldMapper extends FieldMapper {
 
         context.addToFieldNames(fieldType().name());
         for (CompletionInputMetadata metadata : inputMap.values()) {
-            multiFields.parse(
+            multiFields().parse(
                 this,
                 context,
                 () -> context.switchParser(new MultiFieldParser(metadata, fieldType().name(), context.parser().getTokenLocation()))

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

@@ -48,7 +48,7 @@ public class CompositeRuntimeField implements RuntimeField {
         });
 
         private final FieldMapper.Parameter<OnScriptError> onScriptError = FieldMapper.Parameter.onScriptErrorParam(
-            m -> m.onScriptError,
+            m -> m.builderParams.onScriptError(),
             script
         );
 

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

@@ -247,7 +247,10 @@ public final class DateFieldMapper extends FieldMapper {
         private final Parameter<Boolean> ignoreMalformed;
 
         private final Parameter<Script> script = Parameter.scriptParam(m -> toType(m).script);
-        private final Parameter<OnScriptError> onScriptError = Parameter.onScriptErrorParam(m -> toType(m).onScriptError, script);
+        private final Parameter<OnScriptError> onScriptErrorParam = Parameter.onScriptErrorParam(
+            m -> toType(m).builderParams.onScriptError(),
+            script
+        );
 
         private final Resolution resolution;
         private final IndexVersion indexCreatedVersion;
@@ -316,7 +319,17 @@ public final class DateFieldMapper extends FieldMapper {
 
         @Override
         protected Parameter<?>[] getParameters() {
-            return new Parameter<?>[] { index, docValues, store, format, locale, nullValue, ignoreMalformed, script, onScriptError, meta };
+            return new Parameter<?>[] {
+                index,
+                docValues,
+                store,
+                format,
+                locale,
+                nullValue,
+                ignoreMalformed,
+                script,
+                onScriptErrorParam,
+                meta };
         }
 
         private Long parseNullValue(DateFieldType fieldType) {
@@ -364,12 +377,12 @@ public final class DateFieldMapper extends FieldMapper {
                 && ignoreMalformed.isConfigured() == false) {
                 ignoreMalformed.setValue(false);
             }
-
+            hasScript = script.get() != null;
+            onScriptError = onScriptErrorParam.get();
             return new DateFieldMapper(
                 leafName(),
                 ft,
-                multiFieldsBuilder.build(this, context),
+                builderParams(this, context),
-                copyTo,
                 nullTimestamp,
                 resolution,
                 context.isSourceSynthetic(),
@@ -874,14 +887,13 @@ public final class DateFieldMapper extends FieldMapper {
     private DateFieldMapper(
         String leafName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         Long nullValue,
         Resolution resolution,
         boolean isSourceSynthetic,
         Builder builder
     ) {
-        super(leafName, mappedFieldType, multiFields, copyTo, builder.script.get() != null, builder.onScriptError.get());
+        super(leafName, mappedFieldType, builderParams);
         this.store = builder.store.getValue();
         this.indexed = builder.index.getValue();
         this.hasDocValues = builder.docValues.getValue();
@@ -998,7 +1010,7 @@ public final class DateFieldMapper extends FieldMapper {
 
     @Override
     public SourceLoader.SyntheticFieldLoader syntheticFieldLoader() {
-        if (hasScript) {
+        if (hasScript()) {
             return SourceLoader.SyntheticFieldLoader.NOTHING;
         }
         if (hasDocValues == false) {
@@ -1010,7 +1022,7 @@ public final class DateFieldMapper extends FieldMapper {
                     + "] doesn't support synthetic source because it doesn't have doc values"
             );
         }
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

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

@@ -925,8 +925,7 @@ public final class DocumentParser {
                 throw new UnsupportedOperationException();
             }
         },
-        FieldMapper.MultiFields.empty(),
+        FieldMapper.BuilderParams.empty()
-        FieldMapper.CopyTo.empty()
     ) {
 
         @Override

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

@@ -45,6 +45,7 @@ import java.util.List;
 import java.util.Locale;
 import java.util.Map;
 import java.util.Objects;
+import java.util.Optional;
 import java.util.Set;
 import java.util.function.BiConsumer;
 import java.util.function.BiFunction;
@@ -75,46 +76,42 @@ public abstract class FieldMapper extends Mapper {
     @SuppressWarnings("rawtypes")
     static final Parameter<?>[] EMPTY_PARAMETERS = new Parameter[0];
 
-    protected final MappedFieldType mappedFieldType;
-    protected final MultiFields multiFields;
-    protected final CopyTo copyTo;
-    protected final boolean hasScript;
-    protected final OnScriptError onScriptError;
-
     /**
-     * @param simpleName        the leaf name of the mapper
-     * @param mappedFieldType   the MappedFieldType associated with this mapper
-     * @param multiFields       sub fields of this mapper
-     * @param copyTo            copyTo fields of this mapper
-     */
-    protected FieldMapper(String simpleName, MappedFieldType mappedFieldType, MultiFields multiFields, CopyTo copyTo) {
-        this(simpleName, mappedFieldType, multiFields, copyTo, false, null);
-    }
-
-    /**
-     * @param simpleName        the leaf name of the mapper
-     * @param mappedFieldType   the MappedFieldType associated with this mapper
      * @param multiFields       sub fields of this mapper
      * @param copyTo            copyTo fields of this mapper
+     * @param sourceKeepMode   mode for storing the field source in synthetic source mode
      * @param hasScript         whether a script is defined for the field
      * @param onScriptError     the behaviour for when the defined script fails at runtime
      */
-    protected FieldMapper(
+    protected record BuilderParams(
-        String simpleName,
-        MappedFieldType mappedFieldType,
         MultiFields multiFields,
         CopyTo copyTo,
+        Optional<SourceKeepMode> sourceKeepMode,
         boolean hasScript,
         OnScriptError onScriptError
     ) {
+        public static BuilderParams empty() {
+            return empty;
+        }
+
+        private static final BuilderParams empty = new BuilderParams(MultiFields.empty(), CopyTo.empty(), Optional.empty(), false, null);
+    }
+
+    protected final MappedFieldType mappedFieldType;
+    protected final BuilderParams builderParams;
+
+    /**
+     * @param simpleName        the leaf name of the mapper
+     * @param params            initialization params for this field mapper
+     */
+    protected FieldMapper(String simpleName, MappedFieldType mappedFieldType, BuilderParams params) {
         super(simpleName);
+        this.mappedFieldType = mappedFieldType;
+        this.builderParams = params;
+
         // could be blank but not empty on indices created < 8.6.0
         assert mappedFieldType.name().isEmpty() == false;
-        this.mappedFieldType = mappedFieldType;
+        assert params.copyTo != null;
-        this.multiFields = multiFields;
-        this.copyTo = Objects.requireNonNull(copyTo);
-        this.hasScript = hasScript;
-        this.onScriptError = onScriptError;
     }
 
     @Override
@@ -135,11 +132,15 @@ public abstract class FieldMapper extends Mapper {
      * List of fields where this field should be copied to
      */
     public CopyTo copyTo() {
-        return copyTo;
+        return builderParams.copyTo;
     }
 
     public MultiFields multiFields() {
-        return multiFields;
+        return builderParams.multiFields;
+    }
+
+    public Optional<SourceKeepMode> sourceKeepMode() {
+        return builderParams.sourceKeepMode;
     }
 
     /**
@@ -178,7 +179,7 @@ public abstract class FieldMapper extends Mapper {
      */
     public void parse(DocumentParserContext context) throws IOException {
         try {
-            if (hasScript) {
+            if (builderParams.hasScript) {
                 throwIndexingWithScriptParam();
             }
 
@@ -188,14 +189,14 @@ public abstract class FieldMapper extends Mapper {
         }
         // TODO: multi fields are really just copy fields, we just need to expose "sub fields" or something that can be part
         // of the mappings
-        if (multiFields.mappers.length != 0) {
+        if (builderParams.multiFields.mappers.length != 0) {
             doParseMultiFields(context);
         }
     }
 
     private void doParseMultiFields(DocumentParserContext context) throws IOException {
         context.path().add(leafName());
-        for (FieldMapper mapper : multiFields.mappers) {
+        for (FieldMapper mapper : builderParams.multiFields.mappers) {
             mapper.parse(context);
         }
         context.path().remove();
@@ -255,7 +256,7 @@ public abstract class FieldMapper extends Mapper {
      * @return whether this field mapper uses a script to generate its values
      */
     public final boolean hasScript() {
-        return hasScript;
+        return builderParams.hasScript;
     }
 
     /**
@@ -276,7 +277,7 @@ public abstract class FieldMapper extends Mapper {
         try {
             indexScriptValues(searchLookup, readerContext, doc, documentParserContext);
         } catch (Exception e) {
-            if (onScriptError == OnScriptError.CONTINUE) {
+            if (builderParams.onScriptError == OnScriptError.CONTINUE) {
                 documentParserContext.addIgnoredField(fullPath());
             } else {
                 throw new DocumentParsingException(XContentLocation.UNKNOWN, "Error executing script on field [" + fullPath() + "]", e);
@@ -308,7 +309,7 @@ public abstract class FieldMapper extends Mapper {
     }
 
     protected Iterator<Mapper> multiFieldsIterator() {
-        return Iterators.forArray(multiFields.mappers);
+        return Iterators.forArray(builderParams.multiFields.mappers);
     }
 
     /**
@@ -424,15 +425,18 @@ public abstract class FieldMapper extends Mapper {
     protected void doXContentBody(XContentBuilder builder, Params params) throws IOException {
         builder.field("type", contentType());
         getMergeBuilder().toXContent(builder, params);
-        multiFields.toXContent(builder, params);
+        builderParams.multiFields.toXContent(builder, params);
-        copyTo.toXContent(builder);
+        builderParams.copyTo.toXContent(builder);
+        if (builderParams.sourceKeepMode.isPresent()) {
+            builderParams.sourceKeepMode.get().toXContent(builder);
+        }
     }
 
     protected abstract String contentType();
 
     @Override
     public int getTotalFieldsCount() {
-        return 1 + Stream.of(multiFields.mappers).mapToInt(FieldMapper::getTotalFieldsCount).sum();
+        return 1 + Stream.of(builderParams.multiFields.mappers).mapToInt(FieldMapper::getTotalFieldsCount).sum();
     }
 
     public Map<String, NamedAnalyzer> indexAnalyzers() {
@@ -487,7 +491,7 @@ public abstract class FieldMapper extends Mapper {
         // If mapper supports synthetic source natively, it overrides this method,
         // so we won't see those here.
         if (syntheticSourceMode() == SyntheticSourceMode.FALLBACK) {
-            if (copyTo.copyToFields().isEmpty() != true) {
+            if (builderParams.copyTo.copyToFields().isEmpty() != true) {
                 throw new IllegalArgumentException(
                     "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
                 );
@@ -1289,6 +1293,9 @@ public abstract class FieldMapper extends Mapper {
 
         protected final MultiFields.Builder multiFieldsBuilder = new MultiFields.Builder();
         protected CopyTo copyTo = CopyTo.EMPTY;
+        protected Optional<SourceKeepMode> sourceKeepMode = Optional.empty();
+        protected boolean hasScript = false;
+        protected OnScriptError onScriptError = null;
 
         /**
          * Creates a new Builder with a field name
@@ -1304,21 +1311,26 @@ public abstract class FieldMapper extends Mapper {
             for (Parameter<?> param : getParameters()) {
                 param.init(initializer);
             }
-            for (FieldMapper subField : initializer.multiFields.mappers) {
+            for (FieldMapper subField : initializer.builderParams.multiFields.mappers) {
                 multiFieldsBuilder.add(subField);
             }
             return this;
         }
 
+        protected BuilderParams builderParams(Mapper.Builder mainFieldBuilder, MapperBuilderContext context) {
+            return new BuilderParams(multiFieldsBuilder.build(mainFieldBuilder, context), copyTo, sourceKeepMode, hasScript, onScriptError);
+        }
+
         protected void merge(FieldMapper in, Conflicts conflicts, MapperMergeContext mapperMergeContext) {
             for (Parameter<?> param : getParameters()) {
                 param.merge(in, conflicts);
             }
             MapperMergeContext childContext = mapperMergeContext.createChildContext(in.leafName(), null);
-            for (FieldMapper newSubField : in.multiFields.mappers) {
+            for (FieldMapper newSubField : in.builderParams.multiFields.mappers) {
                 multiFieldsBuilder.update(newSubField, childContext);
             }
-            this.copyTo = in.copyTo;
+            this.copyTo = in.builderParams.copyTo;
+            this.sourceKeepMode = in.builderParams.sourceKeepMode;
             validate();
         }
 
@@ -1413,6 +1425,11 @@ public abstract class FieldMapper extends Mapper {
                         iterator.remove();
                         continue;
                     }
+                    case SYNTHETIC_SOURCE_KEEP_PARAM -> {
+                        sourceKeepMode = Optional.of(SourceKeepMode.from(XContentMapValues.nodeStringValue(propNode)));
+                        iterator.remove();
+                        continue;
+                    }
                 }
                 Parameter<?> parameter = deprecatedParamsMap.get(propName);
                 if (parameter != null) {

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

@@ -87,7 +87,10 @@ public class GeoPointFieldMapper extends AbstractPointGeometryFieldMapper<GeoPoi
         final Parameter<Boolean> hasDocValues = Parameter.docValuesParam(m -> builder(m).hasDocValues.get(), true);
         final Parameter<Boolean> stored = Parameter.storeParam(m -> builder(m).stored.get(), false);
         private final Parameter<Script> script = Parameter.scriptParam(m -> builder(m).script.get());
-        private final Parameter<OnScriptError> onScriptError = Parameter.onScriptErrorParam(m -> builder(m).onScriptError.get(), script);
+        private final Parameter<OnScriptError> onScriptErrorParam = Parameter.onScriptErrorParam(
+            m -> builder(m).onScriptErrorParam.get(),
+            script
+        );
         final Parameter<Map<String, String>> meta = Parameter.metaParam();
 
         private final ScriptCompiler scriptCompiler;
@@ -152,7 +155,7 @@ public class GeoPointFieldMapper extends AbstractPointGeometryFieldMapper<GeoPoi
                 ignoreZValue,
                 nullValue,
                 script,
-                onScriptError,
+                onScriptErrorParam,
                 meta,
                 dimension,
                 metric };
@@ -217,10 +220,9 @@ public class GeoPointFieldMapper extends AbstractPointGeometryFieldMapper<GeoPoi
                 metric.get(),
                 indexMode
             );
-            if (this.script.get() == null) {
+            hasScript = script.get() != null;
-                return new GeoPointFieldMapper(leafName(), ft, multiFieldsBuilder.build(this, context), copyTo, geoParser, this);
+            onScriptError = onScriptErrorParam.get();
-            }
+            return new GeoPointFieldMapper(leafName(), ft, builderParams(this, context), geoParser, this);
-            return new GeoPointFieldMapper(leafName(), ft, geoParser, this);
         }
 
     }
@@ -248,32 +250,20 @@ public class GeoPointFieldMapper extends AbstractPointGeometryFieldMapper<GeoPoi
     public GeoPointFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         Parser<GeoPoint> parser,
         Builder builder
     ) {
         super(
             simpleName,
             mappedFieldType,
-            multiFields,
+            builderParams,
             builder.ignoreMalformed.get(),
             builder.ignoreZValue.get(),
             builder.nullValue.get(),
-            copyTo,
             parser
         );
         this.builder = builder;
-        this.scriptValues = null;
-        this.indexCreatedVersion = builder.indexCreatedVersion;
-        this.metricType = builder.metric.get();
-        this.indexMode = builder.indexMode;
-        this.indexed = builder.indexed.get();
-    }
-
-    public GeoPointFieldMapper(String simpleName, MappedFieldType mappedFieldType, Parser<GeoPoint> parser, Builder builder) {
-        super(simpleName, mappedFieldType, MultiFields.empty(), CopyTo.empty(), parser, builder.onScriptError.get());
-        this.builder = builder;
         this.scriptValues = builder.scriptValues();
         this.indexCreatedVersion = builder.indexCreatedVersion;
         this.metricType = builder.metric.get();
@@ -308,7 +298,7 @@ public class GeoPointFieldMapper extends AbstractPointGeometryFieldMapper<GeoPoi
         // TODO phase out geohash (which is currently used in the CompletionSuggester)
         // we only expose the geohash value and disallow advancing tokens, hence we can reuse the same parser throughout multiple sub-fields
         DocumentParserContext parserContext = context.switchParser(new GeoHashMultiFieldParser(context.parser(), geometry.geohash()));
-        multiFields.parse(this, context, () -> parserContext);
+        multiFields().parse(this, context, () -> parserContext);
     }
 
     /**
@@ -635,7 +625,7 @@ public class GeoPointFieldMapper extends AbstractPointGeometryFieldMapper<GeoPoi
                     + "] doesn't support synthetic source because it doesn't have doc values"
             );
         }
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

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

@@ -81,7 +81,10 @@ public class IpFieldMapper extends FieldMapper {
             .acceptsNull();
 
         private final Parameter<Script> script = Parameter.scriptParam(m -> toType(m).script);
-        private final Parameter<OnScriptError> onScriptError = Parameter.onScriptErrorParam(m -> toType(m).onScriptError, script);
+        private final Parameter<OnScriptError> onScriptErrorParam = Parameter.onScriptErrorParam(
+            m -> toType(m).builderParams.onScriptError(),
+            script
+        );
 
         private final Parameter<Map<String, String>> meta = Parameter.metaParam();
         private final Parameter<Boolean> dimension;
@@ -162,7 +165,16 @@ public class IpFieldMapper extends FieldMapper {
 
         @Override
         protected Parameter<?>[] getParameters() {
-            return new Parameter<?>[] { indexed, hasDocValues, stored, ignoreMalformed, nullValue, script, onScriptError, meta, dimension };
+            return new Parameter<?>[] {
+                indexed,
+                hasDocValues,
+                stored,
+                ignoreMalformed,
+                nullValue,
+                script,
+                onScriptErrorParam,
+                meta,
+                dimension };
         }
 
         @Override
@@ -170,6 +182,8 @@ public class IpFieldMapper extends FieldMapper {
             if (inheritDimensionParameterFromParentObject(context)) {
                 dimension.setValue(true);
             }
+            hasScript = script.get() != null;
+            onScriptError = onScriptErrorParam.getValue();
             return new IpFieldMapper(
                 leafName(),
                 new IpFieldType(
@@ -182,8 +196,7 @@ public class IpFieldMapper extends FieldMapper {
                     meta.getValue(),
                     dimension.getValue()
                 ),
-                multiFieldsBuilder.build(this, context),
+                builderParams(this, context),
-                copyTo,
                 context.isSourceSynthetic(),
                 this
             );
@@ -494,12 +507,11 @@ public class IpFieldMapper extends FieldMapper {
     private IpFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         boolean storeIgnored,
         Builder builder
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, builder.script.get() != null, builder.onScriptError.get());
+        super(simpleName, mappedFieldType, builderParams);
         this.ignoreMalformedByDefault = builder.ignoreMalformedByDefault;
         this.indexed = builder.indexed.getValue();
         this.hasDocValues = builder.hasDocValues.getValue();
@@ -621,7 +633,7 @@ public class IpFieldMapper extends FieldMapper {
                     + "] doesn't support synthetic source because it doesn't have doc values"
             );
         }
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

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

@@ -182,7 +182,10 @@ public final class KeywordFieldMapper extends FieldMapper {
         private final Parameter<Map<String, String>> meta = Parameter.metaParam();
 
         private final Parameter<Script> script = Parameter.scriptParam(m -> toType(m).script);
-        private final Parameter<OnScriptError> onScriptError = Parameter.onScriptErrorParam(m -> toType(m).onScriptError, script);
+        private final Parameter<OnScriptError> onScriptError = Parameter.onScriptErrorParam(
+            m -> toType(m).builderParams.onScriptError(),
+            script
+        );
         private final Parameter<Boolean> dimension;
 
         private final IndexAnalyzers indexAnalyzers;
@@ -351,12 +354,13 @@ public final class KeywordFieldMapper extends FieldMapper {
                 // deduplicate in the common default case to save some memory
                 fieldtype = Defaults.FIELD_TYPE;
             }
+            super.hasScript = script.get() != null;
+            super.onScriptError = onScriptError.getValue();
             return new KeywordFieldMapper(
                 leafName(),
                 fieldtype,
                 buildFieldType(context, fieldtype),
-                multiFieldsBuilder.build(this, context),
+                builderParams(this, context),
-                copyTo,
                 context.isSourceSynthetic(),
                 this
             );
@@ -865,12 +869,11 @@ public final class KeywordFieldMapper extends FieldMapper {
         String simpleName,
         FieldType fieldType,
         KeywordFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         boolean isSyntheticSource,
         Builder builder
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, builder.script.get() != null, builder.onScriptError.getValue());
+        super(simpleName, mappedFieldType, builderParams);
         assert fieldType.indexOptions().compareTo(IndexOptions.DOCS_AND_FREQS) <= 0;
         this.indexed = builder.indexed.getValue();
         this.hasDocValues = builder.hasDocValues.getValue();
@@ -1048,7 +1051,7 @@ public final class KeywordFieldMapper extends FieldMapper {
         if (hasScript()) {
             return SourceLoader.SyntheticFieldLoader.NOTHING;
         }
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (builderParams.copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

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

@@ -16,7 +16,10 @@ import org.elasticsearch.features.NodeFeature;
 import org.elasticsearch.index.IndexVersion;
 import org.elasticsearch.index.IndexVersions;
 import org.elasticsearch.xcontent.ToXContentFragment;
+import org.elasticsearch.xcontent.XContentBuilder;
 
+import java.io.IOException;
+import java.util.Arrays;
 import java.util.Map;
 import java.util.Objects;
 import java.util.concurrent.ConcurrentHashMap;
@@ -39,6 +42,9 @@ public abstract class Mapper implements ToXContentFragment, Iterable<Mapper> {
         }
 
         static SourceKeepMode from(String input) {
+            if (input == null) {
+                input = "null";
+            }
             if (input.equals(NONE.name)) {
                 return NONE;
             }
@@ -48,7 +54,15 @@ public abstract class Mapper implements ToXContentFragment, Iterable<Mapper> {
             if (input.equals(ARRAYS.name)) {
                 return ARRAYS;
             }
-            throw new IllegalArgumentException("Unknown " + SYNTHETIC_SOURCE_KEEP_PARAM + " value [" + input + "]");
+            throw new IllegalArgumentException(
+                "Unknown "
+                    + SYNTHETIC_SOURCE_KEEP_PARAM
+                    + " value ["
+                    + input
+                    + "], accepted values are ["
+                    + String.join(",", Arrays.stream(SourceKeepMode.values()).map(SourceKeepMode::toString).toList())
+                    + "]"
+            );
         }
 
         @Override
@@ -56,6 +70,10 @@ public abstract class Mapper implements ToXContentFragment, Iterable<Mapper> {
             return name;
         }
 
+        public void toXContent(XContentBuilder builder) throws IOException {
+            builder.field(SYNTHETIC_SOURCE_KEEP_PARAM, name);
+        }
+
         private final String name;
     }
 

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

@@ -174,7 +174,7 @@ public abstract class MetadataFieldMapper extends FieldMapper {
     }
 
     protected MetadataFieldMapper(MappedFieldType mappedFieldType) {
-        super(mappedFieldType.name(), mappedFieldType, MultiFields.empty(), CopyTo.empty(), false, null);
+        super(mappedFieldType.name(), mappedFieldType, BuilderParams.empty());
     }
 
     @Override

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

@@ -100,7 +100,10 @@ public class NumberFieldMapper extends FieldMapper {
         private final Parameter<Number> nullValue;
 
         private final Parameter<Script> script = Parameter.scriptParam(m -> toType(m).script);
-        private final Parameter<OnScriptError> onScriptError = Parameter.onScriptErrorParam(m -> toType(m).onScriptError, script);
+        private final Parameter<OnScriptError> onScriptErrorParam = Parameter.onScriptErrorParam(
+            m -> toType(m).builderParams.onScriptError(),
+            script
+        );
 
         /**
          * Parameter that marks this field as a time series dimension.
@@ -253,7 +256,7 @@ public class NumberFieldMapper extends FieldMapper {
                 coerce,
                 nullValue,
                 script,
-                onScriptError,
+                onScriptErrorParam,
                 meta,
                 dimension,
                 metric };
@@ -266,14 +269,9 @@ public class NumberFieldMapper extends FieldMapper {
             }
 
             MappedFieldType ft = new NumberFieldType(context.buildFullName(leafName()), this);
-            return new NumberFieldMapper(
+            hasScript = script.get() != null;
-                leafName(),
+            onScriptError = onScriptErrorParam.getValue();
-                ft,
+            return new NumberFieldMapper(leafName(), ft, builderParams(this, context), context.isSourceSynthetic(), this);
-                multiFieldsBuilder.build(this, context),
-                copyTo,
-                context.isSourceSynthetic(),
-                this
-            );
         }
     }
 
@@ -1841,12 +1839,11 @@ public class NumberFieldMapper extends FieldMapper {
     private NumberFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         boolean storeMalformedFields,
         Builder builder
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, builder.script.get() != null, builder.onScriptError.getValue());
+        super(simpleName, mappedFieldType, builderParams);
         this.type = builder.type;
         this.indexed = builder.indexed.getValue();
         this.hasDocValues = builder.hasDocValues.getValue();
@@ -2000,7 +1997,7 @@ public class NumberFieldMapper extends FieldMapper {
         if (hasScript()) {
             return SourceLoader.SyntheticFieldLoader.NOTHING;
         }
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (builderParams.copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

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

@@ -91,7 +91,7 @@ public class PlaceHolderFieldMapper extends FieldMapper {
         @Override
         public PlaceHolderFieldMapper build(MapperBuilderContext context) {
             PlaceHolderFieldType mappedFieldType = new PlaceHolderFieldType(context.buildFullName(leafName()), type, Map.of());
-            return new PlaceHolderFieldMapper(leafName(), mappedFieldType, multiFieldsBuilder.build(this, context), copyTo, unknownParams);
+            return new PlaceHolderFieldMapper(leafName(), mappedFieldType, builderParams(this, context), unknownParams);
         }
     }
 
@@ -262,11 +262,10 @@ public class PlaceHolderFieldMapper extends FieldMapper {
     public PlaceHolderFieldMapper(
         String simpleName,
         PlaceHolderFieldType fieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         Map<String, Object> unknownParams
     ) {
-        super(simpleName, fieldType, multiFields, copyTo);
+        super(simpleName, fieldType, builderParams);
         this.unknownParams.putAll(unknownParams);
     }
 

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

@@ -167,7 +167,7 @@ public class RangeFieldMapper extends FieldMapper {
         @Override
         public RangeFieldMapper build(MapperBuilderContext context) {
             RangeFieldType ft = setupFieldType(context);
-            return new RangeFieldMapper(leafName(), ft, multiFieldsBuilder.build(this, context), copyTo, type, this);
+            return new RangeFieldMapper(leafName(), ft, builderParams(this, context), type, this);
         }
     }
 
@@ -342,12 +342,11 @@ public class RangeFieldMapper extends FieldMapper {
     private RangeFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         RangeType type,
         Builder builder
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo);
+        super(simpleName, mappedFieldType, builderParams);
         this.type = type;
         this.index = builder.index.getValue();
         this.hasDocValues = builder.hasDocValues.getValue();
@@ -478,7 +477,7 @@ public class RangeFieldMapper extends FieldMapper {
                     + "] doesn't support synthetic source because it doesn't have doc values"
             );
         }
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

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

@@ -463,7 +463,6 @@ public final class TextFieldMapper extends FieldMapper {
 
         @Override
         public TextFieldMapper build(MapperBuilderContext context) {
-            MultiFields multiFields = multiFieldsBuilder.build(this, context);
             FieldType fieldType = TextParams.buildFieldType(
                 index,
                 store,
@@ -472,15 +471,16 @@ public final class TextFieldMapper extends FieldMapper {
                 indexCreatedVersion.isLegacyIndexVersion() ? () -> false : norms,
                 termVectors
             );
-            TextFieldType tft = buildFieldType(fieldType, multiFields, context, indexCreatedVersion);
+            BuilderParams builderParams = builderParams(this, context);
+            TextFieldType tft = buildFieldType(fieldType, builderParams.multiFields(), context, indexCreatedVersion);
             SubFieldInfo phraseFieldInfo = buildPhraseInfo(fieldType, tft);
             SubFieldInfo prefixFieldInfo = buildPrefixInfo(context, fieldType, tft);
-            for (Mapper mapper : multiFields) {
+            for (Mapper mapper : builderParams.multiFields()) {
                 if (mapper.fullPath().endsWith(FAST_PHRASE_SUFFIX) || mapper.fullPath().endsWith(FAST_PREFIX_SUFFIX)) {
                     throw new MapperParsingException("Cannot use reserved field name [" + mapper.fullPath() + "]");
                 }
             }
-            return new TextFieldMapper(leafName(), fieldType, tft, prefixFieldInfo, phraseFieldInfo, multiFields, copyTo, this);
+            return new TextFieldMapper(leafName(), fieldType, tft, prefixFieldInfo, phraseFieldInfo, builderParams, this);
         }
     }
 
@@ -1215,11 +1215,10 @@ public final class TextFieldMapper extends FieldMapper {
         TextFieldType mappedFieldType,
         SubFieldInfo prefixFieldInfo,
         SubFieldInfo phraseFieldInfo,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         Builder builder
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, false, null);
+        super(simpleName, mappedFieldType, builderParams);
         assert mappedFieldType.getTextSearchInfo().isTokenized();
         assert mappedFieldType.hasDocValues() == false;
         if (fieldType.indexOptions() == IndexOptions.NONE && fieldType().fielddata()) {
@@ -1428,8 +1427,11 @@ public final class TextFieldMapper extends FieldMapper {
         final Builder b = (Builder) getMergeBuilder();
         b.index.toXContent(builder, includeDefaults);
         b.store.toXContent(builder, includeDefaults);
-        this.multiFields.toXContent(builder, params);
+        multiFields().toXContent(builder, params);
-        this.copyTo.toXContent(builder);
+        copyTo().toXContent(builder);
+        if (sourceKeepMode().isPresent()) {
+            sourceKeepMode().get().toXContent(builder);
+        }
         b.meta.toXContent(builder, includeDefaults);
         b.indexOptions.toXContent(builder, includeDefaults);
         b.termVectors.toXContent(builder, includeDefaults);
@@ -1453,7 +1455,7 @@ public final class TextFieldMapper extends FieldMapper {
 
     @Override
     public SourceLoader.SyntheticFieldLoader syntheticFieldLoader() {
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

server/src/main/java/org/elasticsearch/index/mapper/flattened/FlattenedFieldMapper.java

@@ -216,7 +216,7 @@ public final class FlattenedFieldMapper extends FieldMapper {
                 eagerGlobalOrdinals.get(),
                 dimensions.get()
             );
-            return new FlattenedFieldMapper(leafName(), ft, this);
+            return new FlattenedFieldMapper(leafName(), ft, builderParams(this, context), this);
         }
     }
 
@@ -737,8 +737,8 @@ public final class FlattenedFieldMapper extends FieldMapper {
     private final FlattenedFieldParser fieldParser;
     private final Builder builder;
 
-    private FlattenedFieldMapper(String leafName, MappedFieldType mappedFieldType, Builder builder) {
+    private FlattenedFieldMapper(String leafName, MappedFieldType mappedFieldType, BuilderParams builderParams, Builder builder) {
-        super(leafName, mappedFieldType, MultiFields.empty(), CopyTo.empty());
+        super(leafName, mappedFieldType, builderParams);
         this.builder = builder;
         this.fieldParser = new FlattenedFieldParser(
             mappedFieldType.name(),

server/src/main/java/org/elasticsearch/index/mapper/vectors/DenseVectorFieldMapper.java

@@ -297,10 +297,9 @@ public class DenseVectorFieldMapper extends FieldMapper {
                     indexOptions.getValue(),
                     meta.getValue()
                 ),
+                builderParams(this, context),
                 indexOptions.getValue(),
-                indexVersionCreated,
+                indexVersionCreated
-                multiFieldsBuilder.build(this, context),
-                copyTo
             );
         }
     }
@@ -1963,12 +1962,11 @@ public class DenseVectorFieldMapper extends FieldMapper {
     private DenseVectorFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
+        BuilderParams params,
         IndexOptions indexOptions,
-        IndexVersion indexCreatedVersion,
+        IndexVersion indexCreatedVersion
-        MultiFields multiFields,
-        CopyTo copyTo
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo);
+        super(simpleName, mappedFieldType, params);
         this.indexOptions = indexOptions;
         this.indexCreatedVersion = indexCreatedVersion;
     }
@@ -2015,10 +2013,9 @@ public class DenseVectorFieldMapper extends FieldMapper {
             Mapper update = new DenseVectorFieldMapper(
                 leafName(),
                 updatedDenseVectorFieldType,
+                builderParams,
                 indexOptions,
-                indexCreatedVersion,
+                indexCreatedVersion
-                multiFields(),
-                copyTo
             );
             context.addDynamicMapper(update);
             return;
@@ -2162,7 +2159,7 @@ public class DenseVectorFieldMapper extends FieldMapper {
 
     @Override
     public SourceLoader.SyntheticFieldLoader syntheticFieldLoader() {
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

server/src/main/java/org/elasticsearch/index/mapper/vectors/SparseVectorFieldMapper.java

@@ -69,8 +69,7 @@ public class SparseVectorFieldMapper extends FieldMapper {
             return new SparseVectorFieldMapper(
                 leafName(),
                 new SparseVectorFieldType(context.buildFullName(leafName()), meta.getValue()),
-                multiFieldsBuilder.build(this, context),
+                builderParams(this, context)
-                copyTo
             );
         }
     }
@@ -131,8 +130,8 @@ public class SparseVectorFieldMapper extends FieldMapper {
         }
     }
 
-    private SparseVectorFieldMapper(String simpleName, MappedFieldType mappedFieldType, MultiFields multiFields, CopyTo copyTo) {
+    private SparseVectorFieldMapper(String simpleName, MappedFieldType mappedFieldType, BuilderParams builderParams) {
-        super(simpleName, mappedFieldType, multiFields, copyTo, false, null);
+        super(simpleName, mappedFieldType, builderParams);
     }
 
     @Override

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

@@ -96,7 +96,7 @@ public class MappingLookupInferenceFieldMapperTests extends MapperServiceTestCas
         public static final String CONTENT_TYPE = "test_inference_field";
 
         TestInferenceFieldMapper(String simpleName) {
-            super(simpleName, new TestInferenceFieldMapperFieldType(simpleName), MultiFields.empty(), CopyTo.empty());
+            super(simpleName, new TestInferenceFieldMapperFieldType(simpleName), BuilderParams.empty());
         }
 
         @Override

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

@@ -257,7 +257,7 @@ public class MappingLookupTests extends ESTestCase {
         final String indexedValue;
 
         FakeFieldMapper(FakeFieldType fieldType, String indexedValue) {
-            super(fieldType.name(), fieldType, MultiFields.empty(), CopyTo.empty());
+            super(fieldType.name(), fieldType, BuilderParams.empty());
             this.indexedValue = indexedValue;
         }
 

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

@@ -69,7 +69,7 @@ public class NonDynamicFieldMapperTests extends NonDynamicFieldMapperTestCase {
         }
 
         private NonDynamicFieldMapper(String simpleName, MappedFieldType mappedFieldType) {
-            super(simpleName, mappedFieldType, MultiFields.empty(), CopyTo.empty());
+            super(simpleName, mappedFieldType, BuilderParams.empty());
         }
 
         @Override

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

@@ -187,7 +187,7 @@ public final class ObjectMapperMergeTests extends ESTestCase {
         final TextFieldMapper textFieldMapper = (TextFieldMapper) metrics.getMapper("host.name");
         assertEquals("foo.metrics.host.name", textFieldMapper.fullPath());
         assertEquals("host.name", textFieldMapper.leafName());
-        FieldMapper fieldMapper = textFieldMapper.multiFields.iterator().next();
+        FieldMapper fieldMapper = textFieldMapper.multiFields().iterator().next();
         assertEquals("foo.metrics.host.name.keyword", fieldMapper.fullPath());
         assertEquals("keyword", fieldMapper.leafName());
     }
@@ -361,7 +361,7 @@ public final class ObjectMapperMergeTests extends ESTestCase {
         );
         assertEquals("host.name", textKeywordMultiField.leafName());
         assertEquals("foo.metrics.host.name", textKeywordMultiField.fullPath());
-        FieldMapper fieldMapper = textKeywordMultiField.multiFields.iterator().next();
+        FieldMapper fieldMapper = textKeywordMultiField.multiFields().iterator().next();
         assertEquals("keyword", fieldMapper.leafName());
         assertEquals("foo.metrics.host.name.keyword", fieldMapper.fullPath());
         return new ObjectMapper.Builder("foo", ObjectMapper.Defaults.SUBOBJECTS).add(

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

@@ -176,7 +176,7 @@ public class ParametrizedMapperTests extends MapperServiceTestCase {
 
         @Override
         public FieldMapper build(MapperBuilderContext context) {
-            return new TestMapper(leafName(), context.buildFullName(leafName()), multiFieldsBuilder.build(this, context), copyTo, this);
+            return new TestMapper(leafName(), context.buildFullName(leafName()), builderParams(this, context), this);
         }
     }
 
@@ -205,14 +205,8 @@ public class ParametrizedMapperTests extends MapperServiceTestCase {
         private final DummyEnumType enumField;
         private final DummyEnumType restrictedEnumField;
 
-        protected TestMapper(
+        protected TestMapper(String simpleName, String fullName, BuilderParams builderParams, ParametrizedMapperTests.Builder builder) {
-            String simpleName,
+            super(simpleName, new KeywordFieldMapper.KeywordFieldType(fullName), builderParams);
-            String fullName,
-            MultiFields multiFields,
-            CopyTo copyTo,
-            ParametrizedMapperTests.Builder builder
-        ) {
-            super(simpleName, new KeywordFieldMapper.KeywordFieldType(fullName), multiFields, copyTo);
             this.fixed = builder.fixed.getValue();
             this.fixed2 = builder.fixed2.getValue();
             this.variable = builder.variable.getValue();
@@ -433,6 +427,28 @@ public class ParametrizedMapperTests extends MapperServiceTestCase {
             {"field":{"type":"test_mapper","variable":"updated","required":"value"}}""", Strings.toString(noCopyTo));
     }
 
+    public void testStoredSource() {
+        String mapping = """
+            {"type":"test_mapper","variable":"foo","required":"value","synthetic_source_keep":"none"}""";
+        TestMapper mapper = fromMapping(mapping);
+        assertEquals("{\"field\":" + mapping + "}", Strings.toString(mapper));
+
+        mapping = """
+            {"type":"test_mapper","variable":"foo","required":"value","synthetic_source_keep":"arrays"}""";
+        mapper = fromMapping(mapping);
+        assertEquals("{\"field\":" + mapping + "}", Strings.toString(mapper));
+
+        mapping = """
+            {"type":"test_mapper","variable":"foo","required":"value","synthetic_source_keep":"all"}""";
+        mapper = fromMapping(mapping);
+        assertEquals("{\"field\":" + mapping + "}", Strings.toString(mapper));
+
+        String mappingThrows = """
+            {"type":"test_mapper","variable":"foo","required":"value","synthetic_source_keep":"no-such-value"}""";
+        IllegalArgumentException e = expectThrows(IllegalArgumentException.class, () -> fromMapping(mappingThrows));
+        assertEquals("Unknown synthetic_source_keep value [no-such-value], accepted values are [none,arrays,all]", e.getMessage());
+    }
+
     public void testNullables() {
         String mapping = """
             {"type":"test_mapper","fixed":null,"required":"value"}""";

test/framework/src/main/java/org/elasticsearch/index/mapper/MockFieldMapper.java

@@ -21,15 +21,15 @@ public class MockFieldMapper extends FieldMapper {
     }
 
     public MockFieldMapper(MappedFieldType fieldType) {
-        this(findSimpleName(fieldType.name()), fieldType, MultiFields.empty(), CopyTo.empty());
+        this(findSimpleName(fieldType.name()), fieldType, BuilderParams.empty());
     }
 
     public MockFieldMapper(MappedFieldType fieldType, String simpleName) {
-        super(simpleName, fieldType, MultiFields.empty(), CopyTo.empty(), false, null);
+        super(simpleName, fieldType, BuilderParams.empty());
     }
 
-    public MockFieldMapper(String fullName, MappedFieldType fieldType, MultiFields multifields, CopyTo copyTo) {
+    public MockFieldMapper(String fullName, MappedFieldType fieldType, BuilderParams params) {
-        super(findSimpleName(fullName), fieldType, multifields, copyTo, false, null);
+        super(findSimpleName(fullName), fieldType, params);
     }
 
     @Override
@@ -91,8 +91,7 @@ public class MockFieldMapper extends FieldMapper {
 
         @Override
         public MockFieldMapper build(MapperBuilderContext context) {
-            MultiFields multiFields = multiFieldsBuilder.build(this, context);
+            return new MockFieldMapper(leafName(), fieldType, builderParams(this, context));
-            return new MockFieldMapper(leafName(), fieldType, multiFields, copyTo);
         }
     }
 }

test/framework/src/main/java/org/elasticsearch/index/mapper/NumberFieldMapperTests.java

@@ -75,7 +75,7 @@ public abstract class NumberFieldMapperTests extends MapperTestCase {
                 minimalMapping(b);
                 b.field("script", "test");
                 b.field("on_script_error", "continue");
-            }, m -> assertThat((m).onScriptError, is(OnScriptError.CONTINUE)));
+            }, m -> assertThat((m).builderParams.onScriptError(), is(OnScriptError.CONTINUE)));
         }
     }
 

x-pack/plugin/analytics/src/main/java/org/elasticsearch/xpack/analytics/mapper/HistogramFieldMapper.java

@@ -98,8 +98,7 @@ public class HistogramFieldMapper extends FieldMapper {
             return new HistogramFieldMapper(
                 leafName(),
                 new HistogramFieldType(context.buildFullName(leafName()), meta.getValue()),
-                multiFieldsBuilder.build(this, context),
+                builderParams(this, context),
-                copyTo,
                 this
             );
         }
@@ -113,14 +112,8 @@ public class HistogramFieldMapper extends FieldMapper {
     private final Explicit<Boolean> ignoreMalformed;
     private final boolean ignoreMalformedByDefault;
 
-    public HistogramFieldMapper(
+    public HistogramFieldMapper(String simpleName, MappedFieldType mappedFieldType, BuilderParams builderParams, Builder builder) {
-        String simpleName,
+        super(simpleName, mappedFieldType, builderParams);
-        MappedFieldType mappedFieldType,
-        MultiFields multiFields,
-        CopyTo copyTo,
-        Builder builder
-    ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo);
         this.ignoreMalformed = builder.ignoreMalformed.getValue();
         this.ignoreMalformedByDefault = builder.ignoreMalformed.getDefaultValue().value();
     }
@@ -513,7 +506,7 @@ public class HistogramFieldMapper extends FieldMapper {
 
     @Override
     public SourceLoader.SyntheticFieldLoader syntheticFieldLoader() {
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [histogram] doesn't support synthetic source because it declares copy_to"
             );

x-pack/plugin/inference/src/main/java/org/elasticsearch/xpack/inference/mapper/SemanticTextFieldMapper.java

@@ -170,13 +170,13 @@ public class SemanticTextFieldMapper extends FieldMapper implements InferenceFie
                     indexVersionCreated,
                     meta.getValue()
                 ),
-                copyTo
+                builderParams(this, context)
             );
         }
     }
 
-    private SemanticTextFieldMapper(String simpleName, MappedFieldType mappedFieldType, CopyTo copyTo) {
+    private SemanticTextFieldMapper(String simpleName, MappedFieldType mappedFieldType, BuilderParams builderParams) {
-        super(simpleName, mappedFieldType, MultiFields.empty(), copyTo);
+        super(simpleName, mappedFieldType, builderParams);
     }
 
     @Override

x-pack/plugin/mapper-aggregate-metric/src/main/java/org/elasticsearch/xpack/aggregatemetric/mapper/AggregateDoubleMetricFieldMapper.java

@@ -267,7 +267,7 @@ public class AggregateDoubleMetricFieldMapper extends FieldMapper {
             metricFieldType.setMetricFields(metricFields);
             metricFieldType.setDefaultMetric(defaultMetric.getValue());
 
-            return new AggregateDoubleMetricFieldMapper(leafName(), metricFieldType, metricMappers, this);
+            return new AggregateDoubleMetricFieldMapper(leafName(), metricFieldType, metricMappers, builderParams(this, context), this);
         }
     }
 
@@ -543,9 +543,10 @@ public class AggregateDoubleMetricFieldMapper extends FieldMapper {
         String simpleName,
         MappedFieldType mappedFieldType,
         EnumMap<Metric, NumberFieldMapper> metricFieldMappers,
+        BuilderParams builderParams,
         Builder builder
     ) {
-        super(simpleName, mappedFieldType, MultiFields.empty(), CopyTo.empty());
+        super(simpleName, mappedFieldType, builderParams);
         this.ignoreMalformed = builder.ignoreMalformed.getValue();
         this.ignoreMalformedByDefault = builder.ignoreMalformed.getDefaultValue();
         this.metrics = builder.metrics.getValue();

x-pack/plugin/mapper-constant-keyword/src/main/java/org/elasticsearch/xpack/constantkeyword/mapper/ConstantKeywordFieldMapper.java

@@ -111,7 +111,8 @@ public class ConstantKeywordFieldMapper extends FieldMapper {
             }
             return new ConstantKeywordFieldMapper(
                 leafName(),
-                new ConstantKeywordFieldType(context.buildFullName(leafName()), value.getValue(), meta.getValue())
+                new ConstantKeywordFieldType(context.buildFullName(leafName()), value.getValue(), meta.getValue()),
+                builderParams(this, context)
             );
         }
     }
@@ -301,8 +302,8 @@ public class ConstantKeywordFieldMapper extends FieldMapper {
 
     }
 
-    ConstantKeywordFieldMapper(String simpleName, MappedFieldType mappedFieldType) {
+    ConstantKeywordFieldMapper(String simpleName, MappedFieldType mappedFieldType, BuilderParams builderParams) {
-        super(simpleName, mappedFieldType, MultiFields.empty(), CopyTo.empty());
+        super(simpleName, mappedFieldType, builderParams);
     }
 
     @Override
@@ -321,7 +322,7 @@ public class ConstantKeywordFieldMapper extends FieldMapper {
 
         if (fieldType().value == null) {
             ConstantKeywordFieldType newFieldType = new ConstantKeywordFieldType(fieldType().name(), value, fieldType().meta());
-            Mapper update = new ConstantKeywordFieldMapper(leafName(), newFieldType);
+            Mapper update = new ConstantKeywordFieldMapper(leafName(), newFieldType, builderParams);
             boolean dynamicMapperAdded = context.addDynamicMapper(update);
             // the mapper is already part of the mapping, we're just updating it with the new value
             assert dynamicMapperAdded;

x-pack/plugin/mapper-counted-keyword/src/main/java/org/elasticsearch/xpack/countedkeyword/CountedKeywordFieldMapper.java

@@ -307,8 +307,7 @@ public class CountedKeywordFieldMapper extends FieldMapper {
                     meta.getValue(),
                     countFieldMapper.fieldType()
                 ),
-                multiFieldsBuilder.build(this, context),
+                builderParams(this, context),
-                copyTo,
                 countFieldMapper
             );
         }
@@ -323,11 +322,10 @@ public class CountedKeywordFieldMapper extends FieldMapper {
         String simpleName,
         FieldType fieldType,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         BinaryFieldMapper countFieldMapper
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo);
+        super(simpleName, mappedFieldType, builderParams);
         this.fieldType = fieldType;
         this.countFieldMapper = countFieldMapper;
     }

x-pack/plugin/mapper-unsigned-long/src/main/java/org/elasticsearch/xpack/unsignedlong/UnsignedLongFieldMapper.java

@@ -210,14 +210,7 @@ public class UnsignedLongFieldMapper extends FieldMapper {
                 metric.getValue(),
                 indexMode
             );
-            return new UnsignedLongFieldMapper(
+            return new UnsignedLongFieldMapper(leafName(), fieldType, builderParams(this, context), context.isSourceSynthetic(), this);
-                leafName(),
-                fieldType,
-                multiFieldsBuilder.build(this, context),
-                copyTo,
-                context.isSourceSynthetic(),
-                this
-            );
         }
     }
 
@@ -577,12 +570,11 @@ public class UnsignedLongFieldMapper extends FieldMapper {
     private UnsignedLongFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         boolean isSourceSynthetic,
         Builder builder
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo);
+        super(simpleName, mappedFieldType, builderParams);
         this.isSourceSynthetic = isSourceSynthetic;
         this.indexed = builder.indexed.getValue();
         this.hasDocValues = builder.hasDocValues.getValue();
@@ -776,7 +768,7 @@ public class UnsignedLongFieldMapper extends FieldMapper {
                     + "] doesn't support synthetic source because it doesn't have doc values"
             );
         }
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

x-pack/plugin/mapper-version/src/main/java/org/elasticsearch/xpack/versionfield/VersionStringFieldMapper.java

@@ -119,13 +119,7 @@ public class VersionStringFieldMapper extends FieldMapper {
         @Override
         public VersionStringFieldMapper build(MapperBuilderContext context) {
             FieldType fieldtype = new FieldType(Defaults.FIELD_TYPE);
-            return new VersionStringFieldMapper(
+            return new VersionStringFieldMapper(leafName(), fieldtype, buildFieldType(context, fieldtype), builderParams(this, context));
-                leafName(),
-                fieldtype,
-                buildFieldType(context, fieldtype),
-                multiFieldsBuilder.build(this, context),
-                copyTo
-            );
         }
 
         @Override
@@ -361,14 +355,8 @@ public class VersionStringFieldMapper extends FieldMapper {
 
     private final FieldType fieldType;
 
-    private VersionStringFieldMapper(
+    private VersionStringFieldMapper(String simpleName, FieldType fieldType, MappedFieldType mappedFieldType, BuilderParams buildParams) {
-        String simpleName,
+        super(simpleName, mappedFieldType, buildParams);
-        FieldType fieldType,
-        MappedFieldType mappedFieldType,
-        MultiFields multiFields,
-        CopyTo copyTo
-    ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo);
         this.fieldType = freezeAndDeduplicateFieldType(fieldType);
     }
 
@@ -453,7 +441,7 @@ public class VersionStringFieldMapper extends FieldMapper {
 
     @Override
     public SourceLoader.SyntheticFieldLoader syntheticFieldLoader() {
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );

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

@@ -111,7 +111,7 @@ public class GeoShapeWithDocValuesFieldMapper extends AbstractShapeGeometryField
         final Parameter<Explicit<Boolean>> coerce;
         final Parameter<Explicit<Orientation>> orientation = orientationParam(m -> builder(m).orientation.get());
         private final Parameter<Script> script = Parameter.scriptParam(m -> builder(m).script.get());
-        private final Parameter<OnScriptError> onScriptError = Parameter.onScriptErrorParam(m -> builder(m).onScriptError.get(), script);
+        private final Parameter<OnScriptError> onScriptErrorParam = Parameter.onScriptErrorParam(m -> builder(m).onScriptError, script);
         final Parameter<Map<String, String>> meta = Parameter.metaParam();
         private final ScriptCompiler scriptCompiler;
         private final IndexVersion version;
@@ -152,7 +152,7 @@ public class GeoShapeWithDocValuesFieldMapper extends AbstractShapeGeometryField
                 coerce,
                 orientation,
                 script,
-                onScriptError,
+                onScriptErrorParam,
                 meta };
         }
 
@@ -194,29 +194,17 @@ public class GeoShapeWithDocValuesFieldMapper extends AbstractShapeGeometryField
                 geoFormatterFactory,
                 meta.get()
             );
-            if (script.get() == null) {
+            hasScript = script.get() != null;
+            onScriptError = onScriptErrorParam.get();
             return new GeoShapeWithDocValuesFieldMapper(
                 leafName(),
                 ft,
-                    multiFieldsBuilder.build(this, context),
+                builderParams(this, context),
-                    copyTo,
                 new GeoShapeIndexer(orientation.get().value(), ft.name()),
                 parser,
                 this
             );
         }
-            return new GeoShapeWithDocValuesFieldMapper(
-                leafName(),
-                ft,
-                multiFieldsBuilder.build(this, context),
-                copyTo,
-                new GeoShapeIndexer(orientation.get().value(), ft.name()),
-                parser,
-                onScriptError.get(),
-                this
-            );
-        }
-
     }
 
     public static final class GeoShapeWithDocValuesFieldType extends AbstractShapeGeometryFieldType<Geometry> implements GeoShapeQueryable {
@@ -365,8 +353,7 @@ public class GeoShapeWithDocValuesFieldMapper extends AbstractShapeGeometryField
     public GeoShapeWithDocValuesFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         GeoShapeIndexer indexer,
         GeoShapeParser parser,
         Builder builder
@@ -374,33 +361,17 @@ public class GeoShapeWithDocValuesFieldMapper extends AbstractShapeGeometryField
         super(
             simpleName,
             mappedFieldType,
+            builderParams,
             builder.ignoreMalformed.get(),
             builder.coerce.get(),
             builder.ignoreZValue.get(),
             builder.orientation.get(),
-            multiFields,
-            copyTo,
             parser
         );
         this.builder = builder;
         this.indexer = indexer;
     }
 
-    protected GeoShapeWithDocValuesFieldMapper(
-        String simpleName,
-        MappedFieldType mappedFieldType,
-        MultiFields multiFields,
-        CopyTo copyTo,
-        GeoShapeIndexer indexer,
-        Parser<Geometry> parser,
-        OnScriptError onScriptError,
-        Builder builder
-    ) {
-        super(simpleName, mappedFieldType, multiFields, builder.coerce.get(), builder.orientation.get(), copyTo, parser, onScriptError);
-        this.builder = builder;
-        this.indexer = indexer;
-    }
-
     @Override
     protected void index(DocumentParserContext context, Geometry geometry) {
         // TODO: Make common with the index method ShapeFieldMapper

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

@@ -116,7 +116,7 @@ public class PointFieldMapper extends AbstractPointGeometryFieldMapper<Cartesian
                 nullValue.get(),
                 meta.get()
             );
-            return new PointFieldMapper(leafName(), ft, multiFieldsBuilder.build(this, context), copyTo, parser, this);
+            return new PointFieldMapper(leafName(), ft, builderParams(this, context), parser, this);
         }
 
     }
@@ -128,19 +128,17 @@ public class PointFieldMapper extends AbstractPointGeometryFieldMapper<Cartesian
     public PointFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         CartesianPointParser parser,
         Builder builder
     ) {
         super(
             simpleName,
             mappedFieldType,
-            multiFields,
+            builderParams,
             builder.ignoreMalformed.get(),
             builder.ignoreZValue.get(),
             builder.nullValue.get(),
-            copyTo,
             parser
         );
         this.builder = builder;

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

@@ -122,7 +122,7 @@ public class ShapeFieldMapper extends AbstractShapeGeometryFieldMapper<Geometry>
                 parser,
                 meta.get()
             );
-            return new ShapeFieldMapper(leafName(), ft, multiFieldsBuilder.build(this, context), copyTo, parser, this);
+            return new ShapeFieldMapper(leafName(), ft, builderParams(this, context), parser, this);
         }
     }
 
@@ -192,20 +192,18 @@ public class ShapeFieldMapper extends AbstractShapeGeometryFieldMapper<Geometry>
     public ShapeFieldMapper(
         String simpleName,
         MappedFieldType mappedFieldType,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         Parser<Geometry> parser,
         Builder builder
     ) {
         super(
             simpleName,
             mappedFieldType,
+            builderParams,
             builder.ignoreMalformed.get(),
             builder.coerce.get(),
             builder.ignoreZValue.get(),
             builder.orientation.get(),
-            multiFields,
-            copyTo,
             parser
         );
         this.builder = builder;

x-pack/plugin/wildcard/src/main/java/org/elasticsearch/xpack/wildcard/mapper/WildcardFieldMapper.java

@@ -246,8 +246,7 @@ public class WildcardFieldMapper extends FieldMapper {
                 ),
                 ignoreAbove.get(),
                 context.isSourceSynthetic(),
-                multiFieldsBuilder.build(this, context),
+                builderParams(this, context),
-                copyTo,
                 nullValue.get(),
                 indexVersionCreated
             );
@@ -902,12 +901,11 @@ public class WildcardFieldMapper extends FieldMapper {
         WildcardFieldType mappedFieldType,
         int ignoreAbove,
         boolean storeIgnored,
-        MultiFields multiFields,
+        BuilderParams builderParams,
-        CopyTo copyTo,
         String nullValue,
         IndexVersion indexVersionCreated
     ) {
-        super(simpleName, mappedFieldType, multiFields, copyTo);
+        super(simpleName, mappedFieldType, builderParams);
         this.nullValue = nullValue;
         this.ignoreAbove = ignoreAbove;
         this.storeIgnored = storeIgnored;
@@ -996,7 +994,7 @@ public class WildcardFieldMapper extends FieldMapper {
 
     @Override
     public SourceLoader.SyntheticFieldLoader syntheticFieldLoader() {
-        if (copyTo.copyToFields().isEmpty() != true) {
+        if (copyTo().copyToFields().isEmpty() != true) {
             throw new IllegalArgumentException(
                 "field [" + fullPath() + "] of type [" + typeName() + "] doesn't support synthetic source because it declares copy_to"
             );