From a687b1409c52ba6434d357067793b4c13732f872 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Yoann=20Rodi=C3=A8re?= <yoann@hibernate.org>
Date: Wed, 10 Jun 2020 14:36:25 +0200
Subject: [PATCH] HSEARCH-3476 Use a dedicated object to store the context for
 the projection DSL

Mainly for consistency with all the other search DSLs.
---
 .../elasticsearch/ElasticsearchExtension.java | 12 +++---
 ...sticsearchSearchProjectionFactoryImpl.java | 13 +++---
 .../backend/lucene/LuceneExtension.java       | 12 +++---
 .../LuceneSearchProjectionFactoryImpl.java    | 11 ++---
 .../scope/impl/MappedIndexScopeImpl.java      |  5 ++-
 .../dsl/SearchProjectionFactoryExtension.java |  6 +--
 .../CompositeProjectionOptionsStepImpl.java   | 20 +++++----
 .../impl/DefaultSearchProjectionFactory.java  | 34 ++++++++-------
 ...istanceToFieldProjectionValueStepImpl.java |  7 ++--
 ...entReferenceProjectionOptionsStepImpl.java |  6 +--
 .../impl/EntityProjectionOptionsStepImpl.java |  6 +--
 ...ityReferenceProjectionOptionsStepImpl.java |  6 +--
 .../impl/FieldProjectionValueStepImpl.java    |  7 ++--
 .../impl/ScoreProjectionOptionsStepImpl.java  |  6 +--
 .../impl/SearchProjectionDslContextImpl.java  | 41 +++++++++++++++++++
 .../SearchProjectionFactoryExtensionStep.java | 10 ++---
 .../dsl/spi/SearchProjectionDslContext.java   | 24 +++++++++++
 .../spi/AbstractSearchQuerySelectStep.java    |  5 ++-
 .../search/projection/SearchProjectionIT.java | 10 ++---
 19 files changed, 160 insertions(+), 81 deletions(-)
 create mode 100644 engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/SearchProjectionDslContextImpl.java
 create mode 100644 engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/spi/SearchProjectionDslContext.java

diff --git a/backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/ElasticsearchExtension.java b/backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/ElasticsearchExtension.java
index c77f20baf9b..99440138918 100644
--- a/backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/ElasticsearchExtension.java
+++ b/backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/ElasticsearchExtension.java
@@ -41,7 +41,7 @@
 import org.hibernate.search.engine.search.predicate.dsl.spi.SearchPredicateDslContext;
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactory;
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactoryExtension;
-import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 import org.hibernate.search.engine.search.query.SearchQuery;
 import org.hibernate.search.engine.search.query.SearchQueryExtension;
 import org.hibernate.search.engine.search.query.dsl.SearchQueryDslExtension;
@@ -186,11 +186,13 @@ public Optional<ElasticsearchSearchSortFactory> extendOptional(
 	 * {@inheritDoc}
 	 */
 	@Override
-	public Optional<ElasticsearchSearchProjectionFactory<R, E>> extendOptional(
-			SearchProjectionFactory<R, E> original, SearchProjectionBuilderFactory factory) {
-		if ( factory instanceof ElasticsearchSearchProjectionBuilderFactory ) {
+	@SuppressWarnings("unchecked") // If the factory is an instance of ElasticsearchSearchProjectionBuilderFactory, the cast is safe
+	public Optional<ElasticsearchSearchProjectionFactory<R, E>> extendOptional(SearchProjectionFactory<R, E> original,
+			SearchProjectionDslContext<?> dslContext) {
+		if ( dslContext.builderFactory() instanceof ElasticsearchSearchProjectionBuilderFactory ) {
 			return Optional.of( new ElasticsearchSearchProjectionFactoryImpl<>(
-					original, (ElasticsearchSearchProjectionBuilderFactory) factory
+					original,
+					(SearchProjectionDslContext<ElasticsearchSearchProjectionBuilderFactory>) dslContext
 			) );
 		}
 		else {
diff --git a/backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/search/projection/dsl/impl/ElasticsearchSearchProjectionFactoryImpl.java b/backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/search/projection/dsl/impl/ElasticsearchSearchProjectionFactoryImpl.java
index d1fff45887f..4835cfddaf1 100644
--- a/backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/search/projection/dsl/impl/ElasticsearchSearchProjectionFactoryImpl.java
+++ b/backend/elasticsearch/src/main/java/org/hibernate/search/backend/elasticsearch/search/projection/dsl/impl/ElasticsearchSearchProjectionFactoryImpl.java
@@ -11,6 +11,7 @@
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactory;
 import org.hibernate.search.engine.search.projection.dsl.ProjectionFinalStep;
 import org.hibernate.search.engine.search.projection.dsl.spi.DelegatingSearchProjectionFactory;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 import org.hibernate.search.engine.search.projection.dsl.spi.StaticProjectionFinalStep;
 
 import com.google.gson.JsonObject;
@@ -19,26 +20,26 @@ public class ElasticsearchSearchProjectionFactoryImpl<R, E>
 		extends DelegatingSearchProjectionFactory<R, E>
 		implements ElasticsearchSearchProjectionFactory<R, E> {
 
-	private final ElasticsearchSearchProjectionBuilderFactory factory;
+	private final SearchProjectionDslContext<ElasticsearchSearchProjectionBuilderFactory> dslContext;
 
 	public ElasticsearchSearchProjectionFactoryImpl(SearchProjectionFactory<R, E> delegate,
-			ElasticsearchSearchProjectionBuilderFactory factory) {
+			SearchProjectionDslContext<ElasticsearchSearchProjectionBuilderFactory> dslContext) {
 		super( delegate );
-		this.factory = factory;
+		this.dslContext = dslContext;
 	}
 
 	@Override
 	public ProjectionFinalStep<JsonObject> source() {
-		return new StaticProjectionFinalStep<>( factory.source() );
+		return new StaticProjectionFinalStep<>( dslContext.builderFactory().source() );
 	}
 
 	@Override
 	public ProjectionFinalStep<JsonObject> explanation() {
-		return new StaticProjectionFinalStep<>( factory.explanation() );
+		return new StaticProjectionFinalStep<>( dslContext.builderFactory().explanation() );
 	}
 
 	@Override
 	public ProjectionFinalStep<JsonObject> jsonHit() {
-		return new StaticProjectionFinalStep<>( factory.jsonHit() );
+		return new StaticProjectionFinalStep<>( dslContext.builderFactory().jsonHit() );
 	}
 }
diff --git a/backend/lucene/src/main/java/org/hibernate/search/backend/lucene/LuceneExtension.java b/backend/lucene/src/main/java/org/hibernate/search/backend/lucene/LuceneExtension.java
index 6af07f8bdab..1b1f48f2291 100644
--- a/backend/lucene/src/main/java/org/hibernate/search/backend/lucene/LuceneExtension.java
+++ b/backend/lucene/src/main/java/org/hibernate/search/backend/lucene/LuceneExtension.java
@@ -38,6 +38,7 @@
 import org.hibernate.search.engine.search.predicate.dsl.spi.SearchPredicateDslContext;
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactory;
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactoryExtension;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 import org.hibernate.search.engine.search.query.dsl.SearchQueryDslExtension;
 import org.hibernate.search.engine.search.query.dsl.SearchQuerySelectStep;
 import org.hibernate.search.engine.search.sort.dsl.SearchSortFactory;
@@ -46,7 +47,6 @@
 import org.hibernate.search.engine.backend.scope.spi.IndexScope;
 import org.hibernate.search.engine.search.loading.context.spi.LoadingContext;
 import org.hibernate.search.engine.search.loading.context.spi.LoadingContextBuilder;
-import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
 import org.hibernate.search.engine.search.query.SearchQuery;
 import org.hibernate.search.engine.search.query.SearchQueryExtension;
 import org.hibernate.search.util.common.logging.impl.LoggerFactory;
@@ -186,11 +186,13 @@ public Optional<LuceneSearchSortFactory> extendOptional(
 	 * {@inheritDoc}
 	 */
 	@Override
-	public Optional<LuceneSearchProjectionFactory<R, E>> extendOptional(
-			SearchProjectionFactory<R, E> original, SearchProjectionBuilderFactory factory) {
-		if ( factory instanceof LuceneSearchProjectionBuilderFactory ) {
+	@SuppressWarnings("unchecked") // If the factory is an instance of LuceneSearchProjectionBuilderFactory, the cast is safe
+	public Optional<LuceneSearchProjectionFactory<R, E>> extendOptional(SearchProjectionFactory<R, E> original,
+			SearchProjectionDslContext<?> dslContext) {
+		if ( dslContext.builderFactory() instanceof LuceneSearchProjectionBuilderFactory ) {
 			return Optional.of( new LuceneSearchProjectionFactoryImpl<>(
-					original, (LuceneSearchProjectionBuilderFactory) factory
+					original,
+					(SearchProjectionDslContext<LuceneSearchProjectionBuilderFactory>) dslContext
 			) );
 		}
 		else {
diff --git a/backend/lucene/src/main/java/org/hibernate/search/backend/lucene/search/projection/dsl/impl/LuceneSearchProjectionFactoryImpl.java b/backend/lucene/src/main/java/org/hibernate/search/backend/lucene/search/projection/dsl/impl/LuceneSearchProjectionFactoryImpl.java
index ba84279f785..3b53c21ca81 100644
--- a/backend/lucene/src/main/java/org/hibernate/search/backend/lucene/search/projection/dsl/impl/LuceneSearchProjectionFactoryImpl.java
+++ b/backend/lucene/src/main/java/org/hibernate/search/backend/lucene/search/projection/dsl/impl/LuceneSearchProjectionFactoryImpl.java
@@ -11,6 +11,7 @@
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactory;
 import org.hibernate.search.engine.search.projection.dsl.ProjectionFinalStep;
 import org.hibernate.search.engine.search.projection.dsl.spi.DelegatingSearchProjectionFactory;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 import org.hibernate.search.engine.search.projection.dsl.spi.StaticProjectionFinalStep;
 
 import org.apache.lucene.document.Document;
@@ -20,21 +21,21 @@ public class LuceneSearchProjectionFactoryImpl<R, E>
 		extends DelegatingSearchProjectionFactory<R, E>
 		implements LuceneSearchProjectionFactory<R, E> {
 
-	private final LuceneSearchProjectionBuilderFactory factory;
+	private final SearchProjectionDslContext<LuceneSearchProjectionBuilderFactory> dslContext;
 
 	public LuceneSearchProjectionFactoryImpl(SearchProjectionFactory<R, E> delegate,
-			LuceneSearchProjectionBuilderFactory factory) {
+			SearchProjectionDslContext<LuceneSearchProjectionBuilderFactory> dslContext) {
 		super( delegate );
-		this.factory = factory;
+		this.dslContext = dslContext;
 	}
 
 	@Override
 	public ProjectionFinalStep<Document> document() {
-		return new StaticProjectionFinalStep<>( factory.document() );
+		return new StaticProjectionFinalStep<>( dslContext.builderFactory().document() );
 	}
 
 	@Override
 	public ProjectionFinalStep<Explanation> explanation() {
-		return new StaticProjectionFinalStep<>( factory.explanation() );
+		return new StaticProjectionFinalStep<>( dslContext.builderFactory().explanation() );
 	}
 }
diff --git a/engine/src/main/java/org/hibernate/search/engine/mapper/scope/impl/MappedIndexScopeImpl.java b/engine/src/main/java/org/hibernate/search/engine/mapper/scope/impl/MappedIndexScopeImpl.java
index ba22758994b..694d14fae90 100644
--- a/engine/src/main/java/org/hibernate/search/engine/mapper/scope/impl/MappedIndexScopeImpl.java
+++ b/engine/src/main/java/org/hibernate/search/engine/mapper/scope/impl/MappedIndexScopeImpl.java
@@ -18,6 +18,7 @@
 import org.hibernate.search.engine.search.predicate.dsl.impl.SearchPredicateDslContextImpl;
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactory;
 import org.hibernate.search.engine.search.projection.dsl.impl.DefaultSearchProjectionFactory;
+import org.hibernate.search.engine.search.projection.dsl.impl.SearchProjectionDslContextImpl;
 import org.hibernate.search.engine.search.query.dsl.SearchQuerySelectStep;
 import org.hibernate.search.engine.search.query.dsl.impl.DefaultSearchQuerySelectStep;
 import org.hibernate.search.engine.search.sort.dsl.SearchSortFactory;
@@ -64,7 +65,9 @@ public SearchSortFactory sort() {
 
 	@Override
 	public SearchProjectionFactory<R, E> projection() {
-		return new DefaultSearchProjectionFactory<>( delegate.searchProjectionFactory() );
+		return new DefaultSearchProjectionFactory<>(
+				SearchProjectionDslContextImpl.root( delegate.searchProjectionFactory() )
+		);
 	}
 
 	@Override
diff --git a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/SearchProjectionFactoryExtension.java b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/SearchProjectionFactoryExtension.java
index ad139569c3e..64dd9bf618b 100644
--- a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/SearchProjectionFactoryExtension.java
+++ b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/SearchProjectionFactoryExtension.java
@@ -10,7 +10,7 @@
 import java.util.Optional;
 
 import org.hibernate.search.engine.search.projection.dsl.spi.DelegatingSearchProjectionFactory;
-import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 
 /**
  * An extension to the search projection DSL, allowing the use of non-standard projections in a query.
@@ -36,11 +36,11 @@ public interface SearchProjectionFactoryExtension<T, R, E> {
 	 * <strong>WARNING:</strong> this method is not API, see comments at the type level.
 	 *
 	 * @param original The original, non-extended {@link SearchProjectionFactory}.
-	 * @param factory A {@link SearchProjectionBuilderFactory}.
+	 * @param dslContext A {@link SearchProjectionDslContext}.
 	 * @return An optional containing the extended projection factory ({@link T}) in case
 	 * of success, or an empty optional otherwise.
 	 */
 	Optional<T> extendOptional(SearchProjectionFactory<R, E> original,
-			SearchProjectionBuilderFactory factory);
+			SearchProjectionDslContext<?> dslContext);
 
 }
diff --git a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/CompositeProjectionOptionsStepImpl.java b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/CompositeProjectionOptionsStepImpl.java
index 4595aeb467c..806a604f21e 100644
--- a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/CompositeProjectionOptionsStepImpl.java
+++ b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/CompositeProjectionOptionsStepImpl.java
@@ -12,8 +12,8 @@
 
 import org.hibernate.search.engine.search.projection.SearchProjection;
 import org.hibernate.search.engine.search.projection.dsl.CompositeProjectionOptionsStep;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 import org.hibernate.search.engine.search.projection.spi.CompositeProjectionBuilder;
-import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
 import org.hibernate.search.util.common.function.TriFunction;
 
 
@@ -22,31 +22,33 @@ public class CompositeProjectionOptionsStepImpl<T>
 
 	private final CompositeProjectionBuilder<T> compositeProjectionBuilder;
 
-	public CompositeProjectionOptionsStepImpl(SearchProjectionBuilderFactory factory,
+	public CompositeProjectionOptionsStepImpl(SearchProjectionDslContext<?> dslContext,
 			Function<List<?>, T> transformer,
 			SearchProjection<?>[] projections) {
-		this.compositeProjectionBuilder = factory.composite( transformer, projections );
+		this.compositeProjectionBuilder = dslContext.builderFactory().composite( transformer, projections );
 	}
 
-	public <P> CompositeProjectionOptionsStepImpl(SearchProjectionBuilderFactory factory,
+	public <P> CompositeProjectionOptionsStepImpl(SearchProjectionDslContext<?> dslContext,
 			Function<P, T> transformer,
 			SearchProjection<P> projection) {
-		this.compositeProjectionBuilder = factory.composite( transformer, projection );
+		this.compositeProjectionBuilder = dslContext.builderFactory().composite( transformer, projection );
 	}
 
-	public <P1, P2> CompositeProjectionOptionsStepImpl(SearchProjectionBuilderFactory factory,
+	public <P1, P2> CompositeProjectionOptionsStepImpl(SearchProjectionDslContext<?> dslContext,
 			BiFunction<P1, P2, T> transformer,
 			SearchProjection<P1> projection1,
 			SearchProjection<P2> projection2) {
-		this.compositeProjectionBuilder = factory.composite( transformer, projection1, projection2 );
+		this.compositeProjectionBuilder = dslContext.builderFactory()
+				.composite( transformer, projection1, projection2 );
 	}
 
-	public <P1, P2, P3> CompositeProjectionOptionsStepImpl(SearchProjectionBuilderFactory factory,
+	public <P1, P2, P3> CompositeProjectionOptionsStepImpl(SearchProjectionDslContext<?> dslContext,
 			TriFunction<P1, P2, P3, T> transformer,
 			SearchProjection<P1> projection1,
 			SearchProjection<P2> projection2,
 			SearchProjection<P3> projection3) {
-		this.compositeProjectionBuilder = factory.composite( transformer, projection1, projection2, projection3 );
+		this.compositeProjectionBuilder = dslContext.builderFactory()
+				.composite( transformer, projection1, projection2, projection3 );
 	}
 
 	@Override
diff --git a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/DefaultSearchProjectionFactory.java b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/DefaultSearchProjectionFactory.java
index 17cbe900b07..ccf81151d91 100644
--- a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/DefaultSearchProjectionFactory.java
+++ b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/DefaultSearchProjectionFactory.java
@@ -23,7 +23,7 @@
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactoryExtension;
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactoryExtensionIfSupportedStep;
 import org.hibernate.search.engine.search.common.ValueConvert;
-import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 import org.hibernate.search.engine.spatial.GeoPoint;
 import org.hibernate.search.util.common.function.TriFunction;
 import org.hibernate.search.util.common.impl.Contracts;
@@ -31,22 +31,21 @@
 
 public class DefaultSearchProjectionFactory<R, E> implements SearchProjectionFactory<R, E> {
 
-	private final SearchProjectionBuilderFactory factory;
+	private final SearchProjectionDslContext<?> dslContext;
 
-	public DefaultSearchProjectionFactory(SearchProjectionBuilderFactory factory) {
-		this.factory = factory;
+	public DefaultSearchProjectionFactory(SearchProjectionDslContext<?> dslContext) {
+		this.dslContext = dslContext;
 	}
 
 	@Override
 	public DocumentReferenceProjectionOptionsStep<?> documentReference() {
-		return new DocumentReferenceProjectionOptionsStepImpl( factory );
+		return new DocumentReferenceProjectionOptionsStepImpl( dslContext );
 	}
 
 	@Override
 	public <T> FieldProjectionValueStep<?, T> field(String absoluteFieldPath, Class<T> clazz, ValueConvert convert) {
 		Contracts.assertNotNull( clazz, "clazz" );
-
-		return new FieldProjectionValueStepImpl<>( factory, absoluteFieldPath, clazz, convert );
+		return new FieldProjectionValueStepImpl<>( dslContext, absoluteFieldPath, clazz, convert );
 	}
 
 	@Override
@@ -56,24 +55,23 @@ public FieldProjectionValueStep<?, Object> field(String absoluteFieldPath, Value
 
 	@Override
 	public EntityReferenceProjectionOptionsStep<?, R> entityReference() {
-		return new EntityReferenceProjectionOptionsStepImpl<>( factory );
+		return new EntityReferenceProjectionOptionsStepImpl<>( dslContext );
 	}
 
 	@Override
 	public EntityProjectionOptionsStep<?, E> entity() {
-		return new EntityProjectionOptionsStepImpl<>( factory );
+		return new EntityProjectionOptionsStepImpl<>( dslContext );
 	}
 
 	@Override
 	public ScoreProjectionOptionsStep<?> score() {
-		return new ScoreProjectionOptionsStepImpl( factory );
+		return new ScoreProjectionOptionsStepImpl( dslContext );
 	}
 
 	@Override
 	public DistanceToFieldProjectionValueStep<?, Double> distance(String absoluteFieldPath, GeoPoint center) {
 		Contracts.assertNotNull( center, "center" );
-
-		return new DistanceToFieldProjectionValueStepImpl( factory, absoluteFieldPath, center );
+		return new DistanceToFieldProjectionValueStepImpl( dslContext, absoluteFieldPath, center );
 	}
 
 	@Override
@@ -82,7 +80,7 @@ public <T> CompositeProjectionOptionsStep<?, T> composite(Function<List<?>, T> t
 		Contracts.assertNotNull( transformer, "transformer" );
 		Contracts.assertNotNullNorEmpty( projections, "projections" );
 
-		return new CompositeProjectionOptionsStepImpl<>( factory, transformer, projections );
+		return new CompositeProjectionOptionsStepImpl<>( dslContext, transformer, projections );
 	}
 
 	@Override
@@ -90,7 +88,7 @@ public <P, T> CompositeProjectionOptionsStep<?, T> composite(Function<P, T> tran
 		Contracts.assertNotNull( transformer, "transformer" );
 		Contracts.assertNotNull( projection, "projection" );
 
-		return new CompositeProjectionOptionsStepImpl<>( factory, transformer, projection );
+		return new CompositeProjectionOptionsStepImpl<>( dslContext, transformer, projection );
 	}
 
 	@Override
@@ -100,7 +98,7 @@ public <P1, P2, T> CompositeProjectionOptionsStep<?, T> composite(BiFunction<P1,
 		Contracts.assertNotNull( projection1, "projection1" );
 		Contracts.assertNotNull( projection2, "projection2" );
 
-		return new CompositeProjectionOptionsStepImpl<>( factory, transformer, projection1, projection2 );
+		return new CompositeProjectionOptionsStepImpl<>( dslContext, transformer, projection1, projection2 );
 	}
 
 	@Override
@@ -111,18 +109,18 @@ public <P1, P2, P3, T> CompositeProjectionOptionsStep<?, T> composite(TriFunctio
 		Contracts.assertNotNull( projection2, "projection2" );
 		Contracts.assertNotNull( projection3, "projection3" );
 
-		return new CompositeProjectionOptionsStepImpl<>( factory, transformer, projection1, projection2, projection3 );
+		return new CompositeProjectionOptionsStepImpl<>( dslContext, transformer, projection1, projection2, projection3 );
 	}
 
 	@Override
 	public <T> T extension(SearchProjectionFactoryExtension<T, R, E> extension) {
 		return DslExtensionState.returnIfSupported(
-				extension, extension.extendOptional( this, factory )
+				extension, extension.extendOptional( this, dslContext )
 		);
 	}
 
 	@Override
 	public <T> SearchProjectionFactoryExtensionIfSupportedStep<T, R, E> extension() {
-		return new SearchProjectionFactoryExtensionStep<>( this, factory );
+		return new SearchProjectionFactoryExtensionStep<>( this, dslContext );
 	}
 }
diff --git a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/DistanceToFieldProjectionValueStepImpl.java b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/DistanceToFieldProjectionValueStepImpl.java
index c90e1d34794..336725e916b 100644
--- a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/DistanceToFieldProjectionValueStepImpl.java
+++ b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/DistanceToFieldProjectionValueStepImpl.java
@@ -10,8 +10,8 @@
 
 import org.hibernate.search.engine.search.projection.dsl.DistanceToFieldProjectionOptionsStep;
 import org.hibernate.search.engine.search.projection.dsl.DistanceToFieldProjectionValueStep;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 import org.hibernate.search.engine.search.projection.spi.ListProjectionAccumulator;
-import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
 import org.hibernate.search.engine.search.projection.spi.SingleValuedProjectionAccumulator;
 import org.hibernate.search.engine.spatial.GeoPoint;
 
@@ -19,9 +19,10 @@ public class DistanceToFieldProjectionValueStepImpl
 		extends DistanceToFieldProjectionOptionsStepImpl<Double>
 		implements DistanceToFieldProjectionValueStep<DistanceToFieldProjectionOptionsStepImpl<Double>, Double> {
 
-	DistanceToFieldProjectionValueStepImpl(SearchProjectionBuilderFactory factory, String absoluteFieldPath,
+	DistanceToFieldProjectionValueStepImpl(SearchProjectionDslContext<?> dslContext, String absoluteFieldPath,
 			GeoPoint center) {
-		super( factory.distance( absoluteFieldPath, center ), SingleValuedProjectionAccumulator.provider() );
+		super( dslContext.builderFactory().distance( absoluteFieldPath, center ),
+				SingleValuedProjectionAccumulator.provider() );
 	}
 
 	@Override
diff --git a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/DocumentReferenceProjectionOptionsStepImpl.java b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/DocumentReferenceProjectionOptionsStepImpl.java
index e9d20fd440b..815a5b424ef 100644
--- a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/DocumentReferenceProjectionOptionsStepImpl.java
+++ b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/DocumentReferenceProjectionOptionsStepImpl.java
@@ -9,8 +9,8 @@
 import org.hibernate.search.engine.backend.common.DocumentReference;
 import org.hibernate.search.engine.search.projection.SearchProjection;
 import org.hibernate.search.engine.search.projection.dsl.DocumentReferenceProjectionOptionsStep;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 import org.hibernate.search.engine.search.projection.spi.DocumentReferenceProjectionBuilder;
-import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
 
 
 public class DocumentReferenceProjectionOptionsStepImpl
@@ -18,8 +18,8 @@ public class DocumentReferenceProjectionOptionsStepImpl
 
 	private final DocumentReferenceProjectionBuilder documentReferenceProjectionBuilder;
 
-	DocumentReferenceProjectionOptionsStepImpl(SearchProjectionBuilderFactory factory) {
-		this.documentReferenceProjectionBuilder = factory.documentReference();
+	DocumentReferenceProjectionOptionsStepImpl(SearchProjectionDslContext<?> dslContext) {
+		this.documentReferenceProjectionBuilder = dslContext.builderFactory().documentReference();
 	}
 
 	@Override
diff --git a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/EntityProjectionOptionsStepImpl.java b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/EntityProjectionOptionsStepImpl.java
index 23527d3ece5..f68188090f6 100644
--- a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/EntityProjectionOptionsStepImpl.java
+++ b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/EntityProjectionOptionsStepImpl.java
@@ -8,8 +8,8 @@
 
 import org.hibernate.search.engine.search.projection.SearchProjection;
 import org.hibernate.search.engine.search.projection.dsl.EntityProjectionOptionsStep;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 import org.hibernate.search.engine.search.projection.spi.EntityProjectionBuilder;
-import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
 
 
 public class EntityProjectionOptionsStepImpl<E>
@@ -17,8 +17,8 @@ public class EntityProjectionOptionsStepImpl<E>
 
 	private final EntityProjectionBuilder<E> entityProjectionBuilder;
 
-	EntityProjectionOptionsStepImpl(SearchProjectionBuilderFactory factory) {
-		this.entityProjectionBuilder = factory.entity();
+	EntityProjectionOptionsStepImpl(SearchProjectionDslContext<?> dslContext) {
+		this.entityProjectionBuilder = dslContext.builderFactory().entity();
 	}
 
 	@Override
diff --git a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/EntityReferenceProjectionOptionsStepImpl.java b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/EntityReferenceProjectionOptionsStepImpl.java
index 7443780815b..a897c9ba5e1 100644
--- a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/EntityReferenceProjectionOptionsStepImpl.java
+++ b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/EntityReferenceProjectionOptionsStepImpl.java
@@ -8,8 +8,8 @@
 
 import org.hibernate.search.engine.search.projection.SearchProjection;
 import org.hibernate.search.engine.search.projection.dsl.EntityReferenceProjectionOptionsStep;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 import org.hibernate.search.engine.search.projection.spi.EntityReferenceProjectionBuilder;
-import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
 
 
 public class EntityReferenceProjectionOptionsStepImpl<R>
@@ -17,8 +17,8 @@ public class EntityReferenceProjectionOptionsStepImpl<R>
 
 	private final EntityReferenceProjectionBuilder<R> entityReferenceProjectionBuilder;
 
-	EntityReferenceProjectionOptionsStepImpl(SearchProjectionBuilderFactory factory) {
-		this.entityReferenceProjectionBuilder = factory.entityReference();
+	EntityReferenceProjectionOptionsStepImpl(SearchProjectionDslContext<?> dslContext) {
+		this.entityReferenceProjectionBuilder = dslContext.builderFactory().entityReference();
 	}
 
 	@Override
diff --git a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/FieldProjectionValueStepImpl.java b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/FieldProjectionValueStepImpl.java
index af4accf5537..74f20d7eebd 100644
--- a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/FieldProjectionValueStepImpl.java
+++ b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/FieldProjectionValueStepImpl.java
@@ -12,8 +12,8 @@
 import org.hibernate.search.engine.search.projection.SearchProjection;
 import org.hibernate.search.engine.search.projection.dsl.FieldProjectionOptionsStep;
 import org.hibernate.search.engine.search.projection.dsl.FieldProjectionValueStep;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 import org.hibernate.search.engine.search.projection.spi.ListProjectionAccumulator;
-import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
 import org.hibernate.search.engine.search.projection.spi.SingleValuedProjectionAccumulator;
 
 
@@ -21,9 +21,10 @@ public class FieldProjectionValueStepImpl<T>
 		extends FieldProjectionOptionsStepImpl<T, T>
 		implements FieldProjectionValueStep<FieldProjectionOptionsStepImpl<T, T>, T> {
 
-	FieldProjectionValueStepImpl(SearchProjectionBuilderFactory factory, String absoluteFieldPath, Class<T> clazz,
+	FieldProjectionValueStepImpl(SearchProjectionDslContext<?> dslContext, String absoluteFieldPath, Class<T> clazz,
 			ValueConvert convert) {
-		super( factory.field( absoluteFieldPath, clazz, convert ), SingleValuedProjectionAccumulator.provider() );
+		super( dslContext.builderFactory().field( absoluteFieldPath, clazz, convert ),
+				SingleValuedProjectionAccumulator.provider() );
 	}
 
 	@Override
diff --git a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/ScoreProjectionOptionsStepImpl.java b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/ScoreProjectionOptionsStepImpl.java
index 23ecea359aa..80188f77423 100644
--- a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/ScoreProjectionOptionsStepImpl.java
+++ b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/ScoreProjectionOptionsStepImpl.java
@@ -8,8 +8,8 @@
 
 import org.hibernate.search.engine.search.projection.SearchProjection;
 import org.hibernate.search.engine.search.projection.dsl.ScoreProjectionOptionsStep;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 import org.hibernate.search.engine.search.projection.spi.ScoreProjectionBuilder;
-import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
 
 
 public class ScoreProjectionOptionsStepImpl
@@ -17,8 +17,8 @@ public class ScoreProjectionOptionsStepImpl
 
 	private final ScoreProjectionBuilder scoreProjectionBuilder;
 
-	ScoreProjectionOptionsStepImpl(SearchProjectionBuilderFactory factory) {
-		this.scoreProjectionBuilder = factory.score();
+	ScoreProjectionOptionsStepImpl(SearchProjectionDslContext<?> dslContext) {
+		this.scoreProjectionBuilder = dslContext.builderFactory().score();
 	}
 
 	@Override
diff --git a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/SearchProjectionDslContextImpl.java b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/SearchProjectionDslContextImpl.java
new file mode 100644
index 00000000000..2adc3df9bfe
--- /dev/null
+++ b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/SearchProjectionDslContextImpl.java
@@ -0,0 +1,41 @@
+/*
+ * Hibernate Search, full-text search for your domain model
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.search.engine.search.projection.dsl.impl;
+
+import java.util.function.Function;
+
+import org.hibernate.search.engine.mapper.scope.spi.MappedIndexScope;
+import org.hibernate.search.engine.search.projection.SearchProjection;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
+import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
+import org.hibernate.search.engine.search.query.dsl.SearchQueryOptionsStep;
+
+/**
+ * A DSL context used when building a {@link SearchProjection} object,
+ * either when calling {@link MappedIndexScope#sort()} from a search scope
+ * or when calling {@link SearchQueryOptionsStep#sort(Function)} to build the sort using a lambda
+ * (in which case the lambda may retrieve the resulting {@link SearchProjection} object and cache it).
+ */
+public final class SearchProjectionDslContextImpl<F extends SearchProjectionBuilderFactory>
+		implements SearchProjectionDslContext<F> {
+
+	public static <F extends SearchProjectionBuilderFactory>
+			SearchProjectionDslContext root(F factory) {
+		return new SearchProjectionDslContextImpl<>( factory );
+	}
+
+	private final F factory;
+
+	private SearchProjectionDslContextImpl(F factory) {
+		this.factory = factory;
+	}
+
+	@Override
+	public F builderFactory() {
+		return factory;
+	}
+}
diff --git a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/SearchProjectionFactoryExtensionStep.java b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/SearchProjectionFactoryExtensionStep.java
index 8c8070995ca..acd4988ee0b 100644
--- a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/SearchProjectionFactoryExtensionStep.java
+++ b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/impl/SearchProjectionFactoryExtensionStep.java
@@ -13,27 +13,27 @@
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactoryExtension;
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactoryExtensionIfSupportedMoreStep;
 import org.hibernate.search.engine.search.projection.dsl.ProjectionFinalStep;
-import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 
 public class SearchProjectionFactoryExtensionStep<P, R, E> implements
 		SearchProjectionFactoryExtensionIfSupportedMoreStep<P, R, E> {
 
 	private final SearchProjectionFactory<R, E> parent;
-	private final SearchProjectionBuilderFactory factory;
+	private final SearchProjectionDslContext<?> dslContext;
 
 	private final DslExtensionState<ProjectionFinalStep<P>> state = new DslExtensionState<>();
 
 	SearchProjectionFactoryExtensionStep(SearchProjectionFactory<R, E> parent,
-			SearchProjectionBuilderFactory factory) {
+			SearchProjectionDslContext<?> dslContext) {
 		this.parent = parent;
-		this.factory = factory;
+		this.dslContext = dslContext;
 	}
 
 	@Override
 	public <T> SearchProjectionFactoryExtensionIfSupportedMoreStep<P, R, E> ifSupported(
 			SearchProjectionFactoryExtension<T, R, E> extension,
 			Function<T, ? extends ProjectionFinalStep<P>> projectionContributor) {
-		state.ifSupported( extension, extension.extendOptional( parent, factory ), projectionContributor );
+		state.ifSupported( extension, extension.extendOptional( parent, dslContext ), projectionContributor );
 		return this;
 	}
 
diff --git a/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/spi/SearchProjectionDslContext.java b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/spi/SearchProjectionDslContext.java
new file mode 100644
index 00000000000..01a1f8b97c0
--- /dev/null
+++ b/engine/src/main/java/org/hibernate/search/engine/search/projection/dsl/spi/SearchProjectionDslContext.java
@@ -0,0 +1,24 @@
+/*
+ * Hibernate Search, full-text search for your domain model
+ *
+ * License: GNU Lesser General Public License (LGPL), version 2.1 or later
+ * See the lgpl.txt file in the root directory or <http://www.gnu.org/licenses/lgpl-2.1.html>.
+ */
+package org.hibernate.search.engine.search.projection.dsl.spi;
+
+import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
+
+/**
+ * Represents the current context in the search DSL,
+ * including in particular the projection builder factory.
+ *
+ * @param <F> The type of predicate builder factory.
+ */
+public interface SearchProjectionDslContext<F extends SearchProjectionBuilderFactory> {
+
+	/**
+	 * @return The aggregation builder factory. Will always return the exact same instance.
+	 */
+	F builderFactory();
+
+}
diff --git a/engine/src/main/java/org/hibernate/search/engine/search/query/dsl/spi/AbstractSearchQuerySelectStep.java b/engine/src/main/java/org/hibernate/search/engine/search/query/dsl/spi/AbstractSearchQuerySelectStep.java
index d9cbec4256f..b5fa6614d64 100644
--- a/engine/src/main/java/org/hibernate/search/engine/search/query/dsl/spi/AbstractSearchQuerySelectStep.java
+++ b/engine/src/main/java/org/hibernate/search/engine/search/query/dsl/spi/AbstractSearchQuerySelectStep.java
@@ -11,6 +11,7 @@
 import org.hibernate.search.engine.search.predicate.dsl.SearchPredicateFactory;
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactory;
 import org.hibernate.search.engine.search.projection.dsl.impl.DefaultSearchProjectionFactory;
+import org.hibernate.search.engine.search.projection.dsl.impl.SearchProjectionDslContextImpl;
 import org.hibernate.search.engine.search.query.dsl.SearchQueryOptionsStep;
 import org.hibernate.search.engine.search.query.dsl.SearchQueryDslExtension;
 import org.hibernate.search.engine.search.query.dsl.SearchQuerySelectStep;
@@ -39,7 +40,9 @@ this, indexScope(), sessionContext(), loadingContextBuilder()
 	}
 
 	protected final SearchProjectionFactory<R, E> createDefaultProjectionFactory() {
-		return new DefaultSearchProjectionFactory<>( indexScope().searchProjectionFactory() );
+		return new DefaultSearchProjectionFactory<>(
+				SearchProjectionDslContextImpl.root( indexScope().searchProjectionFactory() )
+		);
 	}
 
 	protected abstract IndexScope<C> indexScope();
diff --git a/integrationtest/backend/tck/src/main/java/org/hibernate/search/integrationtest/backend/tck/search/projection/SearchProjectionIT.java b/integrationtest/backend/tck/src/main/java/org/hibernate/search/integrationtest/backend/tck/search/projection/SearchProjectionIT.java
index 2152da3d3b6..bace9d126b6 100644
--- a/integrationtest/backend/tck/src/main/java/org/hibernate/search/integrationtest/backend/tck/search/projection/SearchProjectionIT.java
+++ b/integrationtest/backend/tck/src/main/java/org/hibernate/search/integrationtest/backend/tck/search/projection/SearchProjectionIT.java
@@ -27,12 +27,12 @@
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactory;
 import org.hibernate.search.engine.search.loading.context.spi.LoadingContext;
 import org.hibernate.search.engine.backend.common.spi.DocumentReferenceConverter;
+import org.hibernate.search.engine.search.projection.dsl.spi.SearchProjectionDslContext;
 import org.hibernate.search.engine.search.query.SearchQuery;
 import org.hibernate.search.engine.search.query.SearchResult;
 import org.hibernate.search.engine.search.projection.dsl.SearchProjectionFactoryExtension;
 import org.hibernate.search.engine.search.projection.dsl.ProjectionFinalStep;
 import org.hibernate.search.engine.search.loading.spi.EntityLoader;
-import org.hibernate.search.engine.search.projection.spi.SearchProjectionBuilderFactory;
 import org.hibernate.search.integrationtest.backend.tck.testsupport.configuration.DefaultAnalysisDefinitions;
 import org.hibernate.search.integrationtest.backend.tck.testsupport.stub.StubDocumentReferenceConverter;
 import org.hibernate.search.integrationtest.backend.tck.testsupport.stub.StubEntityLoader;
@@ -668,9 +668,9 @@ private static class SupportedExtension<R, E>
 			implements SearchProjectionFactoryExtension<MyExtendedFactory<R, E>, R, E> {
 		@Override
 		public Optional<MyExtendedFactory<R, E>> extendOptional(SearchProjectionFactory<R, E> original,
-				SearchProjectionBuilderFactory factory) {
+				SearchProjectionDslContext<?> dslContext) {
 			Assertions.assertThat( original ).isNotNull();
-			Assertions.assertThat( factory ).isNotNull();
+			Assertions.assertThat( dslContext ).isNotNull();
 			return Optional.of( new MyExtendedFactory<>( original ) );
 		}
 	}
@@ -679,9 +679,9 @@ private static class UnSupportedExtension<R, E>
 			implements SearchProjectionFactoryExtension<MyExtendedFactory<R, E>, R, E> {
 		@Override
 		public Optional<MyExtendedFactory<R, E>> extendOptional(SearchProjectionFactory<R, E> original,
-				SearchProjectionBuilderFactory factory) {
+				SearchProjectionDslContext<?> dslContext) {
 			Assertions.assertThat( original ).isNotNull();
-			Assertions.assertThat( factory ).isNotNull();
+			Assertions.assertThat( dslContext ).isNotNull();
 			return Optional.empty();
 		}
 	}