HSEARCH-4253 Implement merging of custom mapping as a post-processing…

… step

To separate concerns. No need to think about it while building the
index model, nor while adding Hibernate-specific metadata: it's just a
post-processing step.

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/document/model/dsl/impl/ElasticsearchIndexObjectFieldBuilder.java

@@ -95,12 +95,7 @@ public void contribute(ElasticsearchIndexNodeCollector collector,
 
 		PropertyMapping mapping = fieldNode.type().createMapping( dynamicType );
 
-		if ( parentMapping.getProperties() != null && parentMapping.getProperties().containsKey( relativeFieldName ) ) {
-			// If the object (node) property is already present on both sides,
-			// we will take the one from the user:
-			mapping = parentMapping.getProperties().get( relativeFieldName );
-		}
-		else if ( IndexFieldInclusion.INCLUDED.equals( fieldNode.inclusion() ) ) {
+		if ( IndexFieldInclusion.INCLUDED.equals( fieldNode.inclusion() ) ) {
 			parentMapping.addProperty( relativeFieldName, mapping );
 		}
 

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/document/model/dsl/impl/ElasticsearchIndexRootBuilder.java

@@ -110,11 +110,17 @@ public void addSchemaRootContributor(IndexSchemaRootContributor schemaRootContri
 	public ElasticsearchIndexModel build() {
 		IndexIdentifier identifier = new IndexIdentifier( idDslConverter, idProjectionConverter );
 
-		RootTypeMapping mapping = rootTypeMapping();
+		RootTypeMapping mapping = new RootTypeMapping();
+		if ( routing != null ) {
+			mapping.setRouting( routing );
+		}
+
 		for ( IndexSchemaRootContributor schemaRootContributor : schemaRootContributors ) {
 			schemaRootContributor.contribute( mapping );
 		}
 
+		mapping.setDynamic( resolveSelfDynamicType( defaultDynamicType ) );
+
 		Map<String, ElasticsearchIndexField> staticFields = new HashMap<>();
 		List<AbstractElasticsearchIndexFieldTemplate<?>> fieldTemplates = new ArrayList<>();
 
@@ -151,7 +157,7 @@ public void collect(NamedDynamicTemplate templateForMapping) {
 
 		return new ElasticsearchIndexModel( indexNames, mappedTypeName, identifier,
 				rootNode, staticFields, fieldTemplates,
-				analysisDefinitionRegistry, customIndexSettings, mapping );
+				analysisDefinitionRegistry, customIndexSettings, mapping, customIndexMapping );
 	}
 
 	@Override
@@ -167,17 +173,4 @@ String getAbsolutePath() {
 	EventContext getIndexEventContext() {
 		return indexEventContext;
 	}
-
-	private RootTypeMapping rootTypeMapping() {
-		if ( customIndexMapping != null ) {
-			return customIndexMapping;
-		}
-
-		RootTypeMapping mapping = new RootTypeMapping();
-		if ( routing != null ) {
-			mapping.setRouting( routing );
-		}
-		mapping.setDynamic( resolveSelfDynamicType( defaultDynamicType ) );
-		return mapping;
-	}
 }

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/document/model/dsl/impl/ElasticsearchIndexValueFieldBuilder.java

@@ -84,11 +84,7 @@ public void contribute(ElasticsearchIndexNodeCollector collector,
 		staticChildrenByNameForParent.put( relativeFieldName, fieldNode );
 		collector.collect( absoluteFieldPath, fieldNode );
 
-		if ( IndexFieldInclusion.INCLUDED.equals( fieldNode.inclusion() ) &&
-				// If the value (leaf) property is already present on both sides,
-				// we will take the one from the user:
-				( parentMapping.getProperties() == null ||
-						!parentMapping.getProperties().containsKey( relativeFieldName ) ) ) {
+		if ( IndexFieldInclusion.INCLUDED.equals( fieldNode.inclusion() ) ) {
 			parentMapping.addProperty( relativeFieldName, type.mapping() );
 		}
 

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/document/model/impl/ElasticsearchIndexModel.java

@@ -28,18 +28,20 @@ public class ElasticsearchIndexModel
 	private final ElasticsearchAnalysisDefinitionRegistry analysisDefinitionRegistry;
 	private final IndexSettings customIndexSettings;
 	private final RootTypeMapping mapping;
+	private final RootTypeMapping customMapping;
 
 	public ElasticsearchIndexModel(IndexNames names, String mappedTypeName,
 			IndexIdentifier identifier,
 			ElasticsearchIndexRoot rootNode, Map<String, ElasticsearchIndexField> staticFields,
 			List<AbstractElasticsearchIndexFieldTemplate<?>> fieldTemplates,
 			ElasticsearchAnalysisDefinitionRegistry analysisDefinitionRegistry, IndexSettings customIndexSettings,
-			RootTypeMapping mapping) {
+			RootTypeMapping mapping, RootTypeMapping customMapping) {
 		super( names.hibernateSearchIndex(), mappedTypeName, identifier, rootNode, staticFields, fieldTemplates );
 		this.names = names;
 		this.analysisDefinitionRegistry = analysisDefinitionRegistry;
 		this.customIndexSettings = customIndexSettings;
 		this.mapping = mapping;
+		this.customMapping = customMapping;
 	}
 
 	@Override
@@ -68,6 +70,7 @@ public void contributeLowLevelMetadata(LowLevelIndexMetadataBuilder builder) {
 		builder.setAnalysisDefinitionRegistry( analysisDefinitionRegistry );
 		builder.setCustomIndexSettings( customIndexSettings );
 		builder.setMapping( mapping );
+		builder.setCustomMapping( customMapping );
 	}
 
 	@Override

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/document/model/lowlevel/impl/LowLevelIndexMetadataBuilder.java

@@ -9,6 +9,8 @@
 import java.util.LinkedHashMap;
 import java.util.Map;
 
+import org.hibernate.search.backend.elasticsearch.gson.impl.GsonUtils;
+import org.hibernate.search.backend.elasticsearch.gson.spi.GsonProvider;
 import org.hibernate.search.backend.elasticsearch.index.layout.impl.IndexNames;
 import org.hibernate.search.backend.elasticsearch.lowlevel.index.aliases.impl.IndexAliasDefinition;
 import org.hibernate.search.backend.elasticsearch.lowlevel.index.impl.IndexMetadata;
@@ -21,13 +23,16 @@
 
 public class LowLevelIndexMetadataBuilder {
 
+	private final GsonProvider gsonProvider;
 	private final ElasticsearchIndexMetadataSyntax syntax;
 	private final IndexNames indexNames;
 	private ElasticsearchAnalysisDefinitionRegistry analysisDefinitionRegistry;
 	private IndexSettings customIndexSettings;
 	private RootTypeMapping mapping;
+	private RootTypeMapping customMapping;
 
-	public LowLevelIndexMetadataBuilder(ElasticsearchIndexMetadataSyntax syntax, IndexNames indexNames) {
+	public LowLevelIndexMetadataBuilder(GsonProvider gsonProvider, ElasticsearchIndexMetadataSyntax syntax, IndexNames indexNames) {
+		this.gsonProvider = gsonProvider;
 		this.syntax = syntax;
 		this.indexNames = indexNames;
 	}
@@ -44,13 +49,17 @@ public void setMapping(RootTypeMapping mapping) {
 		this.mapping = mapping;
 	}
 
+	public void setCustomMapping(RootTypeMapping customMapping) {
+		this.customMapping = customMapping;
+	}
+
 	public IndexMetadata build() {
 		IndexMetadata indexMetadata = new IndexMetadata();
 		indexMetadata.setAliases( buildAliases() );
 
 		indexMetadata.setSettings( buildSettings() );
 
-		indexMetadata.setMapping( mapping );
+		indexMetadata.setMapping( buildMapping() );
 		return indexMetadata;
 	}
 
@@ -90,6 +99,20 @@ private IndexSettings buildSettings() {
 		return settings;
 	}
 
+	private RootTypeMapping buildMapping() {
+		if ( customMapping == null ) {
+			return mapping;
+		}
+		// Avoid side effects: we copy the mappings before modifying them.
+		RootTypeMapping customMappingCopy =
+				GsonUtils.deepCopy( gsonProvider.getGsonNoSerializeNulls(), RootTypeMapping.class, customMapping );
+		RootTypeMapping hibernateSearchMappingCopy =
+				GsonUtils.deepCopy( gsonProvider.getGsonNoSerializeNulls(), RootTypeMapping.class, mapping );
+		// The custom mapping takes precedence over the Hibernate Search one.
+		customMappingCopy.merge( hibernateSearchMappingCopy );
+		return customMappingCopy;
+	}
+
 	/*
 	 * Allows lazy initialization of analysis settings
 	 */

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/gson/impl/GsonUtils.java

@@ -6,6 +6,7 @@
  */
 package org.hibernate.search.backend.elasticsearch.gson.impl;
 
+import com.google.gson.Gson;
 import com.google.gson.JsonArray;
 import com.google.gson.JsonElement;
 import com.google.gson.JsonObject;
@@ -48,4 +49,16 @@ else if ( JsonElementTypes.ARRAY.isInstance( currentValue ) ) {
 		}
 	}
 
+	/**
+	 * Efficiently performs a deep copy of a given object using Gson serialization/deserialization.
+	 * @param gson The {@link Gson} object.
+	 * @param objectType The type of the object to copy.
+	 * @param object The object to copy.
+	 * @param <T> The type of the object to copy.
+	 * @return A deep copy of {@code object}.
+	 */
+	public static <T> T deepCopy(Gson gson, Class<T> objectType, T object) {
+		return gson.fromJson( gson.toJsonTree( object ), objectType );
+	}
+
 }

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/index/impl/IndexManagerBackendContext.java

@@ -177,6 +177,7 @@ EventContext getEventContext() {
 	ElasticsearchIndexSchemaManager createSchemaManager(ElasticsearchIndexModel model,
 			ElasticsearchIndexLifecycleExecutionOptions lifecycleExecutionOptions) {
 		LowLevelIndexMetadataBuilder builder = new LowLevelIndexMetadataBuilder(
+				link.getGsonProvider(),
 				link.getIndexMetadataSyntax(),
 				model.names()
 		);

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/lowlevel/index/mapping/impl/AbstractTypeMapping.java

@@ -75,4 +75,43 @@ public void setExtraAttributes(Map<String, JsonElement> extraAttributes) {
 	public String toString() {
 		return new GsonBuilder().setPrettyPrinting().create().toJson( this );
 	}
+
+	/**
+	 * Merge this mapping with another mapping generated by Hibernate Search:
+	 *
+	 * <ol>
+	 * <li>Mapping parameters other than {@code properties} will be
+	 * those from {@code this}; those from {@code other} will be ignored.
+	 * <li>The mapping parameter {@code properties} will be merged, using properties defined in both {@code this}
+	 * and {@code other}.
+	 * <li>If a property is defined on both sides, it will be merged recursively as described in item 1 and 2.
+	 * </ol>
+	 *
+	 * @param other The other mapping.
+	 */
+	public void merge(AbstractTypeMapping other) {
+		if ( other == null ) {
+			// nothing to do
+			return;
+		}
+
+		Map<String, PropertyMapping> otherProperties = other.properties;
+		if ( otherProperties == null ) {
+			return;
+		}
+
+		for ( Map.Entry<String, PropertyMapping> entry : otherProperties.entrySet() ) {
+			String name = entry.getKey();
+			PropertyMapping thisProperty = properties == null ? null : properties.get( name );
+			PropertyMapping otherProperty = entry.getValue();
+			if ( thisProperty != null ) {
+				// Merge common properties recursively
+				thisProperty.merge( otherProperty );
+			}
+			else {
+				// Add missing properties
+				addProperty( name, otherProperty );
+			}
+		}
+	}
 }

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/mapping/impl/DiscriminatorTypeNameMapping.java

@@ -65,11 +65,6 @@ private static final class TypeNameDiscriminatorSchemaRootContributor
 			implements IndexSchemaRootContributor {
 		@Override
 		public void contribute(RootTypeMapping rootTypeMapping) {
-			if ( rootTypeMapping.getProperties() != null && rootTypeMapping.getProperties().containsKey( MAPPED_TYPE_FIELD_NAME ) ) {
-				// do not override if the property is defined in the user custom mapping
-				return;
-			}
-
 			PropertyMapping mappedTypePropertyMapping = new PropertyMapping();
 			mappedTypePropertyMapping.setType( DataTypes.KEYWORD );
 			mappedTypePropertyMapping.setIndex( false );

backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/multitenancy/impl/DiscriminatorMultiTenancyStrategy.java

@@ -82,23 +82,17 @@ public DiscriminatorMultiTenancyIdProjectionExtractionHelper idProjectionExtract
 	private static class DiscriminatorMultiTenancyIndexSchemaRootContributor implements IndexSchemaRootContributor {
 		@Override
 		public void contribute(RootTypeMapping rootTypeMapping) {
-			// do not override if the property is defined in the user custom mapping
-			if ( rootTypeMapping.getProperties() == null || !rootTypeMapping.getProperties().containsKey( ID_FIELD_NAME ) ) {
-				PropertyMapping idPropertyMapping = new PropertyMapping();
-				idPropertyMapping.setType( DataTypes.KEYWORD );
-				idPropertyMapping.setIndex( false );
-				idPropertyMapping.setDocValues( true );
-				rootTypeMapping.addProperty( ID_FIELD_NAME, idPropertyMapping );
-			}
-
-			// do not override if the property is defined in the user custom mapping
-			if ( rootTypeMapping.getProperties() == null || !rootTypeMapping.getProperties().containsKey( TENANT_ID_FIELD_NAME ) ) {
-				PropertyMapping tenantIdPropertyMapping = new PropertyMapping();
-				tenantIdPropertyMapping.setType( DataTypes.KEYWORD );
-				tenantIdPropertyMapping.setIndex( true );
-				tenantIdPropertyMapping.setDocValues( true );
-				rootTypeMapping.addProperty( TENANT_ID_FIELD_NAME, tenantIdPropertyMapping );
-			}
+			PropertyMapping idPropertyMapping = new PropertyMapping();
+			idPropertyMapping.setType( DataTypes.KEYWORD );
+			idPropertyMapping.setIndex( false );
+			idPropertyMapping.setDocValues( true );
+			rootTypeMapping.addProperty( ID_FIELD_NAME, idPropertyMapping );
+
+			PropertyMapping tenantIdPropertyMapping = new PropertyMapping();
+			tenantIdPropertyMapping.setType( DataTypes.KEYWORD );
+			tenantIdPropertyMapping.setIndex( true );
+			tenantIdPropertyMapping.setDocValues( true );
+			rootTypeMapping.addProperty( TENANT_ID_FIELD_NAME, tenantIdPropertyMapping );
 		}
 	}