HHH-13756 simplify EntityGraphNavigator's navigate() to never return null value

hibernate-core/src/main/java/org/hibernate/loader/ast/internal/LoaderSelectBuilder.java

@@ -431,12 +431,10 @@ public class LoaderSelectBuilder {
 
 			// 'entity graph' takes precedence over 'fetch profile'
 			if ( entityGraphNavigator != null) {
-				navigation = entityGraphNavigator.navigateIfApplicable( fetchParent, fetchable, isKeyFetchable );
+				navigation = entityGraphNavigator.navigate( fetchParent, fetchable, isKeyFetchable );
-				if ( navigation != null ) {
 				fetchTiming = navigation.getFetchStrategy();
 				joined = navigation.isJoined();
 			}
-			}
 			else if ( loadQueryInfluencers.hasEnabledFetchProfiles() ) {
 				if ( fetchParent instanceof EntityResultGraphNode ) {
 					final EntityResultGraphNode entityFetchParent = (EntityResultGraphNode) fetchParent;
@@ -493,7 +491,7 @@ public class LoaderSelectBuilder {
 				if ( !( fetchable instanceof BasicValuedModelPart ) ) {
 					fetchDepth--;
 				}
-				if ( entityGraphNavigator != null && navigation != null ) {
+				if ( entityGraphNavigator != null ) {
 					entityGraphNavigator.backtrack( navigation.getPreviousContext() );
 				}
 			}

hibernate-core/src/main/java/org/hibernate/query/sqm/sql/internal/StandardSqmSelectTranslator.java

@@ -307,12 +307,10 @@ public class StandardSqmSelectTranslator
 			alias = null;
 
 			if ( entityGraphNavigator != null ) {
-				navigation = entityGraphNavigator.navigateIfApplicable( fetchParent, fetchable, isKeyFetchable );
+				navigation = entityGraphNavigator.navigate( fetchParent, fetchable, isKeyFetchable );
-				if ( navigation != null ) {
 				fetchTiming = navigation.getFetchStrategy();
 				joined = navigation.isJoined();
 			}
-			}
 			else if ( fetchInfluencers.hasEnabledFetchProfiles() ) {
 				if ( fetchParent instanceof EntityResultGraphNode ) {
 					final EntityResultGraphNode entityFetchParent = (EntityResultGraphNode) fetchParent;

hibernate-core/src/main/java/org/hibernate/sql/results/graph/EntityGraphNavigator.java

@@ -52,19 +52,18 @@ public interface EntityGraphNavigator {
 	 * Mainly reset the current context entity graph node to the passed method parameter.
 	 *
 	 * @param previousContext The stored previous invocation result; should not be null
-	 * @see #navigateIfApplicable(FetchParent, Fetchable, boolean)
+	 * @see #navigate(FetchParent, Fetchable, boolean)
 	 */
 	void backtrack(GraphImplementor previousContext);
 
 	/**
-	 * Tries to navigate from parent to child node within entity graph and returns non-null {@code NavigateResult}
+	 * Tries to navigate from parent to child node within entity graph and returns non-null {@code NavigateResult}.
-	 * if applicable. Returns null value if not applicable.
 	 *
 	 * @apiNote If applicable, internal state will be mutated. Not thread safe and should be used within single thread.
 	 * @param parent The FetchParent
 	 * @param fetchable The Fetchable
 	 * @param exploreKeySubgraph true if only key sub graph is explored; false if key sub graph is excluded
-	 * @return {@link Navigation} if applicable; null otherwise
+	 * @return resulting {@link Navigation}; never null
 	 */
-	Navigation navigateIfApplicable(FetchParent parent, Fetchable fetchable, boolean exploreKeySubgraph);
+	Navigation navigate(FetchParent parent, Fetchable fetchable, boolean exploreKeySubgraph);
 }

hibernate-core/src/main/java/org/hibernate/sql/results/internal/StandardEntityGraphNavigatorImpl.java

@@ -49,7 +49,7 @@ public class StandardEntityGraphNavigatorImpl implements EntityGraphNavigator {
 	}
 
 	@Override
-	public Navigation navigateIfApplicable(FetchParent fetchParent, Fetchable fetchable, boolean exploreKeySubgraph) {
+	public Navigation navigate(FetchParent fetchParent, Fetchable fetchable, boolean exploreKeySubgraph) {
 		final GraphImplementor previousContextRoot = currentGraphContext;
 		FetchTiming fetchTiming = null;
 		boolean joined = false;
@@ -65,7 +65,6 @@ public class StandardEntityGraphNavigatorImpl implements EntityGraphNavigator {
 				if ( fetchable instanceof PluralAttributeMapping ) {
 					PluralAttributeMapping pluralAttributeMapping = (PluralAttributeMapping) fetchable;
 
-					// avoid '^' bitwise operator to improve code readability
 					assert exploreKeySubgraph && isJpaMapCollectionType( pluralAttributeMapping )
 							|| !exploreKeySubgraph && !isJpaMapCollectionType( pluralAttributeMapping );
 
@@ -83,17 +82,20 @@ public class StandardEntityGraphNavigatorImpl implements EntityGraphNavigator {
 					subgraphMap = attributeNode.getSubGraphMap();
 					subgraphMapKey = fetchable.getJavaTypeDescriptor().getJavaType();
 				}
-				if ( subgraphMap == null || subgraphMapKey == null ) {
+				if ( subgraphMap != null && subgraphMapKey != null ) {
-					currentGraphContext = null;
-				}
-				else {
 					currentGraphContext = subgraphMap.get( subgraphMapKey );
 				}
+				else {
+					currentGraphContext = null;
+				}
 			}
 			else {
 				currentGraphContext = null;
 			}
 		}
+		else {
+			currentGraphContext = null;
+		}
 		if ( fetchTiming == null ) {
 			if ( graphSemantic == GraphSemantic.FETCH ) {
 				fetchTiming = FetchTiming.DELAYED;

hibernate-core/src/test/java/org/hibernate/orm/test/loading/entitygraph/EntityGraphLoadPlanBuilderTest.java

@@ -50,6 +50,7 @@ import org.hibernate.testing.orm.junit.DomainModel;
 import org.hibernate.testing.orm.junit.SessionFactory;
 import org.hibernate.testing.orm.junit.SessionFactoryScope;
 import org.junit.jupiter.api.Test;
+import org.junit.platform.commons.util.CollectionUtils;
 
 import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.hamcrest.CoreMatchers.is;
@@ -262,11 +263,11 @@ public class EntityGraphLoadPlanBuilderTest {
 					assertPluralAttributeJoinedGroup( sqlAst, "shipAddresses", tableGroup -> {
 						assertThat( tableGroup.getTableGroupJoins(), hasSize( 1 ) );
 
-						final TableGroup compositeTableGroup = tableGroup.getTableGroupJoins().iterator().next().getJoinedGroup();
+						final TableGroup compositeTableGroup = CollectionUtils.getOnlyElement( tableGroup.getTableGroupJoins() ).getJoinedGroup();
 						assertThat( compositeTableGroup, instanceOf( CompositeTableGroup.class ) );
 						assertThat( compositeTableGroup.getTableGroupJoins(), hasSize( 1 ) );
 
-						final TableGroup countryTableGroup = compositeTableGroup.getTableGroupJoins().iterator().next().getJoinedGroup();
+						final TableGroup countryTableGroup = CollectionUtils.getOnlyElement( compositeTableGroup.getTableGroupJoins() ).getJoinedGroup();
 						assertThat( countryTableGroup.getModelPart().getPartName(), is( "country" ) );
 
 						assertThat( countryTableGroup.getTableGroupJoins(), isEmpty() );
@@ -315,7 +316,7 @@ public class EntityGraphLoadPlanBuilderTest {
 		final TableGroup rootTableGroup = fromClause.getRoots().get( 0 );
 		assertThat( rootTableGroup.getTableGroupJoins(), hasSize( 1 ) );
 
-		final TableGroup joinedGroup = rootTableGroup.getTableGroupJoins().iterator().next().getJoinedGroup();
+		final TableGroup joinedGroup = CollectionUtils.getOnlyElement( rootTableGroup.getTableGroupJoins() ).getJoinedGroup();
 		assertThat( joinedGroup.getModelPart().getPartName(), is( expectedAttributeName ) );
 		assertThat( joinedGroup.getModelPart().getJavaTypeDescriptor().getJavaType(), assignableTo( expectedEntityJpaClass ) );
 		assertThat( joinedGroup.getModelPart(), instanceOf( EntityValuedModelPart.class ) );
@@ -330,7 +331,7 @@ public class EntityGraphLoadPlanBuilderTest {
 		final TableGroup root = fromClause.getRoots().get( 0 );
 		assertThat( root.getTableGroupJoins(), hasSize( 1 ) );
 
-		final TableGroup joinedGroup = root.getTableGroupJoins().iterator().next().getJoinedGroup();
+		final TableGroup joinedGroup = CollectionUtils.getOnlyElement( root.getTableGroupJoins() ).getJoinedGroup();
 		assertThat( joinedGroup.getModelPart().getPartName(), is( expectedPluralAttributeName ) );
 		assertThat( joinedGroup.getModelPart(), instanceOf( PluralAttributeMapping.class ) );
 		tableGroupConsumer.accept( joinedGroup );
@@ -339,7 +340,7 @@ public class EntityGraphLoadPlanBuilderTest {
 	private void assertPersonHomeAddressJoinedGroup(TableGroup tableGroup) {
 		assertThat( tableGroup.getTableGroupJoins(), hasSize( 1 ) );
 
-		final TableGroup joinedGroup = tableGroup.getTableGroupJoins().iterator().next().getJoinedGroup();
+		final TableGroup joinedGroup = CollectionUtils.getOnlyElement( tableGroup.getTableGroupJoins() ).getJoinedGroup();
 		assertThat( joinedGroup.getModelPart().getPartName(), is( "homeAddress" ) );
 		assertThat( joinedGroup.getModelPart(), instanceOf( EmbeddedAttributeMapping.class ) );
 		assertThat( joinedGroup, instanceOf( CompositeTableGroup.class ) );

hibernate-core/src/test/java/org/hibernate/orm/test/query/hql/entitygraph/HqlEntityGraphTest.java

@@ -28,7 +28,6 @@ import org.hibernate.graph.spi.RootGraphImplementor;
 import org.hibernate.metamodel.mapping.EntityValuedModelPart;
 import org.hibernate.metamodel.mapping.PluralAttributeMapping;
 import org.hibernate.metamodel.mapping.internal.EmbeddedAttributeMapping;
-import org.hibernate.orm.test.loading.entitygraph.EntityGraphLoadPlanBuilderTest;
 import org.hibernate.query.hql.spi.HqlQueryImplementor;
 import org.hibernate.query.spi.QueryImplementor;
 import org.hibernate.query.sqm.internal.QuerySqmImpl;
@@ -440,7 +439,7 @@ public class HqlEntityGraphTest {
 
 	@Embeddable
 	public static class Address {
-		@ManyToOne(fetch = FetchType.EAGER)
+		@ManyToOne
 		Country country;
 	}