some cleanup to SQM selection handling

Author: gavinking

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/select/SqmSelectClause.java

@@ -108,24 +108,18 @@ public void setSelection(SqmSelectableNode<?> selectableNode) {
 
 	public JpaSelection<?> resolveJpaSelection() {
 		// NOTE : JPA's `Selection` contract is really better named `Selectable`
-		if ( selections == null || selections.size() != 1 ) {
-			return this;
-		}
-		else {
-			return selections.get( 0 ).getSelectableNode();
-		}
+		return selections != null && selections.size() == 1 ? selections.get( 0 ).getSelectableNode() : this;
 	}
 
 	@Override
 	public List<SqmSelectableNode<?>> getSelectionItems() {
 		final List<SqmSelectableNode<?>> subSelections = new ArrayList<>();
-
-		if ( this.selections != null ) {
-			if ( this.selections.size() == 1 ) {
-				this.selections.get( 0 ).getSelectableNode().visitSubSelectableNodes( subSelections::add );
+		if ( selections != null ) {
+			if ( selections.size() == 1 ) {
+				selections.get( 0 ).getSelectableNode().visitSubSelectableNodes( subSelections::add );
 			}
 			else {
-				for ( SqmSelection<?> selection : this.selections ) {
+				for ( SqmSelection<?> selection : selections ) {
 					selection.getSelectableNode().visitSubSelectableNodes( subSelections::add );
 				}
 			}

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/select/SqmSelectStatement.java

@@ -180,8 +180,7 @@ public SqmQuerySource getQuerySource() {
 	@Override
 	public SqmQuerySpec<T> getQuerySpec() {
 		if ( querySource == CRITERIA ) {
-			final SqmQueryPart<T> queryPart = getQueryPart();
-			if ( queryPart instanceof SqmQuerySpec<T> querySpec ) {
+			if ( getQueryPart() instanceof SqmQuerySpec<T> querySpec ) {
 				return querySpec;
 			}
 			throw new IllegalStateException(
@@ -355,9 +354,8 @@ public SqmSelectStatement<T> multiselect(Selection<?>... selections) {
 				checkSelectionIsJpaCompliant( selection );
 			}
 		}
-
-		final Selection<? extends T> resultSelection = getResultSelection( selections );
-		getQuerySpec().getSelectClause().setSelection( (SqmSelectableNode<?>) resultSelection );
+		getQuerySpec().getSelectClause()
+				.setSelection( (SqmSelectableNode<?>) getResultSelection( selections ) );
 		return this;
 	}
 
@@ -368,32 +366,29 @@ public SqmSelectStatement<T> multiselect(List<Selection<?>> selectionList) {
 				checkSelectionIsJpaCompliant( selection );
 			}
 		}
-		final Selection<? extends T> resultSelection = getResultSelection( selectionList );
-		getQuerySpec().getSelectClause().setSelection( (SqmSelectableNode<?>) resultSelection );
+		getQuerySpec().getSelectClause()
+				.setSelection( (SqmSelectableNode<?>) getResultSelection( selectionList ) );
 		return this;
 	}
 
-	@SuppressWarnings("unchecked")
-	private Selection<? extends T> getResultSelection(List<?> selections) {
+	private JpaSelection<?> getResultSelection(List<Selection<?>> selections) {
 		final Class<T> resultType = getResultType();
 		if ( resultType == null || resultType == Object.class ) {
-			switch ( selections.size() ) {
-				case 0:
-					throw new IllegalArgumentException( "Empty selections passed to criteria query typed as Object" );
-				case 1:
-					return (Selection<? extends T>) selections.get( 0 );
-				default:
-					return (Selection<? extends T>) nodeBuilder().array( (List<Selection<?>>) selections );
-			}
+			return switch ( selections.size() ) {
+				case 0 -> throw new IllegalArgumentException(
+						"empty selections passed to criteria query typed as Object" );
+				case 1 -> (JpaSelection<?>) selections.get( 0 );
+				default -> nodeBuilder().array( selections );
+			};
 		}
 		else if ( Tuple.class.isAssignableFrom( resultType ) ) {
-			return (Selection<? extends T>) nodeBuilder().tuple( (List<Selection<?>>) selections );
+			return nodeBuilder().tuple( selections );
 		}
 		else if ( resultType.isArray() ) {
-			return nodeBuilder().array( resultType, (List<? extends JpaSelection<?>>) selections );
+			return nodeBuilder().array( resultType, selections );
 		}
 		else {
-			return nodeBuilder().construct( resultType, (List<? extends JpaSelection<?>>) selections );
+			return nodeBuilder().construct( resultType, selections );
 		}
 	}
 
@@ -566,10 +561,12 @@ private <S> void aliasSelections(SqmQueryPart<S> queryPart) {
 			final SqmQuerySpec<S> querySpec = queryPart.getFirstQuerySpec();
 			final LinkedHashSet<JpaSelection<?>> newSelections = new LinkedHashSet<>();
 			aliasSelection( querySpec.getSelection(), newSelections );
+			final JpaSelection<?> selection =
+					newSelections.size() == 1
+							? newSelections.iterator().next()
+							: nodeBuilder().tuple( newSelections.toArray( new JpaSelection<?>[0] ) );
 			//noinspection unchecked
-			querySpec.setSelection( (JpaSelection<S>) ( newSelections.size() == 1 ?
-					newSelections.iterator().next() :
-					nodeBuilder().tuple( newSelections.toArray( new JpaSelection<?>[0] ) ) ) );
+			querySpec.setSelection( (JpaSelection<S>) selection );
 		}
 		else {
 			( (SqmQueryGroup<?>) queryPart ).getQueryParts().forEach( this::aliasSelections );

hibernate-core/src/main/java/org/hibernate/query/sqm/tree/select/SqmSubQuery.java

@@ -274,9 +274,7 @@ public SqmSubQuery<T> select(Expression<T> expression) {
 	@SuppressWarnings("unchecked")
 	public SqmSubQuery<T> multiselect(Selection<?>... selections) {
 		validateComplianceMultiselect();
-
 		final Selection<? extends T> resultSelection = getResultSelection( selections );
-
 		final SqmQuerySpec<T> querySpec = getQuerySpec();
 		if ( querySpec.getSelectClause() == null ) {
 			querySpec.setSelectClause( new SqmSelectClause( false, 1, nodeBuilder() ) );
@@ -286,36 +284,38 @@ public SqmSubQuery<T> multiselect(Selection<?>... selections) {
 	}
 
 	@Override
-	@SuppressWarnings("unchecked")
 	public SqmSubQuery<T> multiselect(List<Selection<?>> selectionList) {
 		validateComplianceMultiselect();
+		final SqmQuerySpec<T> querySpec = getQuerySpec();
+		if ( querySpec.getSelectClause() == null ) {
+			querySpec.setSelectClause( new SqmSelectClause( false, 1, nodeBuilder() ) );
+		}
+		querySpec.setSelection( getResultSelection( selectionList ) );
+		return this;
+	}
 
-		final Selection<? extends T> resultSelection;
+	private JpaSelection<T> getResultSelection(List<Selection<?>> selections) {
 		final Class<T> resultType = getResultType();
-		final List<? extends Selection<?>> selections = (List<? extends JpaSelection<?>>) (List<?>) selectionList;
 		if ( resultType == null || resultType == Object.class ) {
-			resultSelection = switch ( selections.size() ) {
-				case 0 -> throw new IllegalArgumentException( "empty selections passed to criteria query typed as Object" );
-				case 1 -> (Selection<? extends T>) selections.get( 0 );
-				default -> (Selection<? extends T>) nodeBuilder().array( selectionList );
+			final JpaSelection<?> selection = switch ( selections.size() ) {
+				case 0 -> throw new IllegalArgumentException(
+						"empty selections passed to criteria query typed as Object" );
+				case 1 -> (JpaSelection<?>) selections.get( 0 );
+				default -> nodeBuilder().array( selections );
 			};
+			//noinspection unchecked
+			return (JpaSelection<T>) selection;
 		}
 		else if ( Tuple.class.isAssignableFrom( resultType ) ) {
-			resultSelection = ( Selection<? extends T> ) nodeBuilder().tuple( selectionList );
+			//noinspection unchecked
+			return (JpaSelection<T>) nodeBuilder().tuple( selections );
 		}
 		else if ( resultType.isArray() ) {
-			resultSelection = nodeBuilder().array( resultType, selections );
+			return nodeBuilder().array( resultType, selections );
 		}
 		else {
-			resultSelection = nodeBuilder().construct( resultType, selections );
-		}
-		final SqmQuerySpec<T> querySpec = getQuerySpec();
-		if ( querySpec.getSelectClause() == null ) {
-			querySpec.setSelectClause( new SqmSelectClause( false, 1, nodeBuilder() ) );
+			return nodeBuilder().construct( resultType, selections );
 		}
-		querySpec.setSelection( (JpaSelection<T>) resultSelection );
-
-		return this;
 	}
 
 	@Override