support for canonical reference to id and version. consider other entity parts - natural-id, tenant-discriminator, etc

hibernate-core/src/main/antlr/org/hibernate/grammars/hql/HqlLexer.g4

@@ -141,6 +141,10 @@ ARROW :	'->';
 // ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 // Keywords
 
+ID 				: [iI][dD];
+VERSION			: [vV] [eE] [rR] [sS] [iI] [oO] [nN];
+NATURALID		: [nN] [aA] [tT] [uU] [rR] [aA] [lL] [iI] [dD];
+
 ABS					: [aA] [bB] [sS];
 ALL					: [aA] [lL] [lL];
 AND					: [aA] [nN] [dD];

hibernate-core/src/main/antlr/org/hibernate/grammars/hql/HqlParser.g4

@@ -413,6 +413,9 @@ expression
 	| literal									# LiteralExpression
 	| parameter									# ParameterExpression
 	| entityTypeReference						# EntityTypeExpression
+	| entityIdReference							# EntityIdExpression
+	| entityVersionReference					# EntityVersionExpression
+	| entityNaturalIdReference					# EntityNaturalIdExpression
 	| path										# PathExpression
 	| function									# FunctionExpression
 	| LEFT_PAREN subQuery RIGHT_PAREN			# SubQueryExpression
@@ -422,6 +425,18 @@ entityTypeReference
 	: TYPE LEFT_PAREN (path | parameter) RIGHT_PAREN
 	;
 
+entityIdReference
+	: ID LEFT_PAREN path RIGHT_PAREN pathContinuation?
+	;
+
+entityVersionReference
+	: VERSION LEFT_PAREN path RIGHT_PAREN
+	;
+
+entityNaturalIdReference
+	: NATURALID LEFT_PAREN path RIGHT_PAREN pathContinuation?
+	;
+
 caseStatement
 	: simpleCaseStatement
 	| searchedCaseStatement
@@ -987,6 +1002,7 @@ identifier
 	| GREATEST
 	| GROUP
 	| HOUR
+	| ID
 	| IFNULL
 	| IN
 	| INDEX
@@ -1020,6 +1036,7 @@ identifier
 	| MOD
 	| MONTH
 	| NANOSECOND
+	| NATURALID
 	| NEW
 	| NOT
 	| NULLIF
@@ -1056,6 +1073,7 @@ identifier
 	| UPDATE
 	| UPPER
 	| VALUE
+	| VERSION
 	| WEEK
 	| WHERE
 	| WITH

hibernate-core/src/main/java/org/hibernate/query/hql/internal/SemanticQueryBuilder.java

@@ -39,11 +39,13 @@
 import org.hibernate.metamodel.mapping.MappingModelExpressable;
 import org.hibernate.metamodel.model.domain.AllowableFunctionReturnType;
 import org.hibernate.metamodel.model.domain.BasicDomainType;
+import org.hibernate.metamodel.model.domain.DomainType;
 import org.hibernate.metamodel.model.domain.EntityDomainType;
 import org.hibernate.metamodel.model.domain.IdentifiableDomainType;
 import org.hibernate.metamodel.model.domain.ManagedDomainType;
 import org.hibernate.metamodel.model.domain.MapPersistentAttribute;
 import org.hibernate.metamodel.model.domain.PluralPersistentAttribute;
+import org.hibernate.metamodel.model.domain.SingularPersistentAttribute;
 import org.hibernate.query.BinaryArithmeticOperator;
 import org.hibernate.query.ComparisonOperator;
 import org.hibernate.query.PathException;
@@ -1320,6 +1322,70 @@ else if ( ctx.entityTypeReference().path() != null ) {
 		throw new ParsingException( "Could not interpret grammar context as 'entity type' expression : " + ctx.getText() );
 	}
 
+	@Override
+	public SqmPath visitEntityIdExpression(HqlParser.EntityIdExpressionContext ctx) {
+		return visitEntityIdReference( ctx.entityIdReference() );
+	}
+
+	@Override
+	public SqmPath visitEntityIdReference(HqlParser.EntityIdReferenceContext ctx) {
+		final SqmPath sqmPath = consumeDomainPath( ctx.path() );
+		final DomainType sqmPathType = sqmPath.getReferencedPathSource().getSqmPathType();
+
+		if ( sqmPathType instanceof IdentifiableDomainType ) {
+			//noinspection unchecked
+			final SqmPath idPath = ( (IdentifiableDomainType) sqmPathType ).getIdentifierDescriptor().createSqmPath(
+					sqmPath,
+					this
+			);
+
+			if ( ctx.pathContinuation() == null ) {
+				return idPath;
+			}
+
+			throw new NotYetImplementedFor6Exception( "Path continuation from `id()` reference not yet implemented" );
+		}
+
+		throw new SemanticException( "Path does not reference an identifiable-type : " + sqmPath.getNavigablePath().getFullPath() );
+	}
+
+	@Override
+	public SqmPath visitEntityVersionExpression(HqlParser.EntityVersionExpressionContext ctx) {
+		return visitEntityVersionReference( ctx.entityVersionReference() );
+	}
+
+	@Override
+	public SqmPath visitEntityVersionReference(HqlParser.EntityVersionReferenceContext ctx) {
+		final SqmPath sqmPath = consumeDomainPath( ctx.path() );
+		final DomainType sqmPathType = sqmPath.getReferencedPathSource().getSqmPathType();
+
+		if ( sqmPathType instanceof IdentifiableDomainType ) {
+			final IdentifiableDomainType identifiableType = (IdentifiableDomainType) sqmPathType;
+			final SingularPersistentAttribute versionAttribute = identifiableType.findVersionAttribute();
+			if ( versionAttribute == null ) {
+				throw new SemanticException(
+						"`" + sqmPath.getNavigablePath().getFullPath() + "` resolved to an identifiable-type (`" +
+								identifiableType.getTypeName() + "`) which does not define a version"
+				);
+			}
+
+			//noinspection unchecked
+			return versionAttribute.createSqmPath( sqmPath, this );
+		}
+
+		throw new SemanticException( "Path does not reference an identifiable-type : " + sqmPath.getNavigablePath().getFullPath() );
+	}
+
+	@Override
+	public SqmPath visitEntityNaturalIdExpression(HqlParser.EntityNaturalIdExpressionContext ctx) {
+		return visitEntityNaturalIdReference( ctx.entityNaturalIdReference() );
+	}
+
+	@Override
+	public SqmPath visitEntityNaturalIdReference(HqlParser.EntityNaturalIdReferenceContext ctx) {
+		throw new NotYetImplementedFor6Exception( "Support for HQL natural-id references not yet implemented" );
+	}
+
 	@Override
 	@SuppressWarnings("unchecked")
 	public SqmMapEntryReference visitMapEntrySelection(HqlParser.MapEntrySelectionContext ctx) {
@@ -3551,7 +3617,6 @@ public SqmPath visitMapKeyNavigablePath(HqlParser.MapKeyNavigablePathContext ctx
 		return result;
 	}
 
-
 	private SqmPath consumeDomainPath(HqlParser.PathContext parserPath) {
 		final SemanticPathPart consumedPart = (SemanticPathPart) parserPath.accept( this );
 		if ( consumedPart instanceof SqmPath ) {

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

@@ -7,18 +7,16 @@
 package org.hibernate.orm.test.query.hql;
 
 import java.util.List;
-
 import javax.persistence.Entity;
 import javax.persistence.Id;
 
 import org.hibernate.metamodel.model.domain.EntityDomainType;
 import org.hibernate.metamodel.model.domain.SingularPersistentAttribute;
-import org.hibernate.metamodel.model.domain.internal.SingularAttributeImpl;
 import org.hibernate.orm.test.query.sqm.BaseSqmUnitTest;
 import org.hibernate.orm.test.query.sqm.domain.Person;
 import org.hibernate.query.sqm.tree.domain.SqmEntityValuedSimplePath;
-import org.hibernate.query.sqm.tree.domain.SqmSimplePath;
 import org.hibernate.query.sqm.tree.domain.SqmPath;
+import org.hibernate.query.sqm.tree.domain.SqmSimplePath;
 import org.hibernate.query.sqm.tree.expression.SqmExpression;
 import org.hibernate.query.sqm.tree.from.SqmRoot;
 import org.hibernate.query.sqm.tree.predicate.SqmComparisonPredicate;
@@ -29,8 +27,6 @@
 
 import org.junit.jupiter.api.Test;
 
-import org.hamcrest.CoreMatchers;
-
 import static org.hamcrest.CoreMatchers.instanceOf;
 import static org.hamcrest.CoreMatchers.is;
 import static org.hamcrest.CoreMatchers.not;
@@ -112,8 +108,6 @@ public void testEntityIdReferences() {
 		interpretSelect( "select s.mate from Person s where s.id = ?1" );
 		interpretSelect( "select s.mate from Person s where s.pk = ?1" );
 
-		// NOTE: this next form does not (yet) work...
-		interpretSelect( "select s.mate from Person s where s.{id} = ?1" );
 
 		final EntityDomainType<OddOne> entity = sessionFactory().getRuntimeMetamodels()
 				.getJpaMetamodel()
@@ -131,6 +125,14 @@ public void testEntityIdReferences() {
 		assertThat( ( (SqmPath) pkRef ).getJavaType(), sameInstance( String.class ) );
 	}
 
+	@Test
+	public void testCanonicalReferences() {
+		final SqmSelectStatement sqm = interpretSelect( "select s.mate from Person s where id(s) = ?1" );
+		assertThat( sqm.getQuerySpec().getRestriction(), notNullValue() );
+		final SqmComparisonPredicate restriction = (SqmComparisonPredicate) sqm.getQuerySpec().getRestriction();
+		assertThat( restriction, notNullValue() );
+	}
+
 	@Test
 	public void testManyToOneReference() {
 		final SqmSelectStatement sqm = interpretSelect( "select s.mate from Person s" );