fix issue with Criteria queries not defining selections explicitly. should use the (single) root as the selection.

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

@@ -51,8 +51,10 @@ import org.hibernate.query.sqm.tree.SqmDmlStatement;
 import org.hibernate.query.sqm.tree.SqmStatement;
 import org.hibernate.query.sqm.tree.delete.SqmDeleteStatement;
 import org.hibernate.query.sqm.tree.expression.SqmParameter;
+import org.hibernate.query.sqm.tree.from.SqmRoot;
 import org.hibernate.query.sqm.tree.insert.SqmInsertSelectStatement;
 import org.hibernate.query.sqm.tree.insert.SqmInsertStatement;
+import org.hibernate.query.sqm.tree.select.SqmQuerySpec;
 import org.hibernate.query.sqm.tree.select.SqmSelectStatement;
 import org.hibernate.query.sqm.tree.select.SqmSelection;
 import org.hibernate.query.sqm.tree.update.SqmUpdateStatement;
@@ -178,16 +180,36 @@ public class QuerySqmImpl<R>
 			SharedSessionContractImplementor producer) {
 		super( producer );
 
-		if ( resultType != null ) {
 		if ( sqmStatement instanceof SqmSelectStatement ) {
-				//noinspection unchecked
+			final SqmSelectStatement sqmSelectStatement = (SqmSelectStatement) sqmStatement;
+			final SqmQuerySpec sqmQuerySpec = sqmSelectStatement.getQuerySpec();
+			final List<SqmSelection> sqmSelections = sqmQuerySpec.getSelectClause().getSelections();
+
+			// make sure there is at least one root
+			final List<SqmRoot> sqmRoots = sqmQuerySpec.getFromClause().getRoots();
+			if ( sqmRoots == null || sqmRoots.isEmpty() ) {
+				throw new IllegalArgumentException( "Criteria did not define any query roots" );
+			}
+
+			if ( sqmSelections == null || sqmSelections.isEmpty() ) {
+				// if there is a single root, use that as the selection
+				if ( sqmRoots.size() == 1 ) {
+					final SqmRoot sqmRoot = sqmRoots.get( 0 );
+					sqmQuerySpec.getSelectClause().add( sqmRoot, null );
+				}
+				else {
+					throw new IllegalArgumentException(  );
+				}
+			}
+
+			if ( resultType != null ) {
 				checkQueryReturnType( (SqmSelectStatement<R>) sqmStatement, resultType, producer.getFactory() );
 			}
+		}
 		else {
 			assert sqmStatement instanceof SqmDmlStatement;
 			throw new IllegalArgumentException( "Non-select queries cannot be typed" );
 		}
-		}
 
 		this.hqlString = "<criteria>";
 		this.sqmStatement = sqmStatement;

hibernate-core/src/test/java/org/hibernate/orm/test/query/criteria/BasicCriteriaExecutionTests.java

@@ -16,6 +16,7 @@ import javax.persistence.criteria.CriteriaQuery;
 import javax.persistence.criteria.ParameterExpression;
 import javax.persistence.criteria.Root;
 
+import org.hibernate.IrrelevantEntity;
 import org.hibernate.query.criteria.HibernateCriteriaBuilder;
 import org.hibernate.query.criteria.JpaCriteriaQuery;
 import org.hibernate.query.criteria.JpaRoot;
@@ -51,6 +52,18 @@ public class BasicCriteriaExecutionTests extends BaseNonConfigCoreFunctionalTest
 		);
 	}
 
+	@Test
+	public void testIt() {
+		inSession(
+				session -> {
+					CriteriaBuilder criteriaBuilder = session.getCriteriaBuilder();
+					CriteriaQuery<BasicEntity> criteria = criteriaBuilder.createQuery( BasicEntity.class );
+					criteria.from( BasicEntity.class );
+					List<BasicEntity> results = session.createQuery( criteria ).list();
+				}
+		);
+	}
+
 	@Test
 	public void testExecutingBasicCriteriaQueryInStatelessSession() {
 		final CriteriaBuilder criteriaBuilder = sessionFactory().getCriteriaBuilder();