From 70f906045a5279add172d69a3fb258c52425ca6b Mon Sep 17 00:00:00 2001
From: Gavin King <gavin@hibernate.org>
Date: Sun, 31 Mar 2024 14:38:04 +0200
Subject: [PATCH] when CDI is missing, do still add an @Inject annotation on
 the constructor

at least when jakarta.inject is available

Signed-off-by: Gavin King <gavin@hibernate.org>
---
 .../annotation/AnnotationMetaEntity.java      | 19 +++++++++++++++--
 .../annotation/RepositoryConstructor.java     | 21 ++++++++++++++++---
 2 files changed, 35 insertions(+), 5 deletions(-)

diff --git a/tooling/metamodel-generator/src/main/java/org/hibernate/processor/annotation/AnnotationMetaEntity.java b/tooling/metamodel-generator/src/main/java/org/hibernate/processor/annotation/AnnotationMetaEntity.java
index 89e2055675..d74cdaa34c 100644
--- a/tooling/metamodel-generator/src/main/java/org/hibernate/processor/annotation/AnnotationMetaEntity.java
+++ b/tooling/metamodel-generator/src/main/java/org/hibernate/processor/annotation/AnnotationMetaEntity.java
@@ -535,13 +535,28 @@ public class AnnotationMetaEntity extends AnnotationMeta {
 				sessionType = HIB_STATELESS_SESSION;
 				addDaoConstructor( null );
 			}
-			if ( jakartaDataRepository && !quarkusInjection
-					&& context.addDependentAnnotation() ) {
+			if ( needsDefaultConstructor() ) {
 				addDefaultConstructor();
 			}
 		}
 	}
 
+	/**
+	 * For usage with CDI, but outside Quarkus, Jakarta Data
+	 * repositories use {@code @PersistenceUnit} to obtain an
+	 * {@code EntityManagerFactory} via field injection. So in
+	 * that case we will need a {@link DefaultConstructor default
+	 * constructor}. We don't do this in Quarkus, because there
+	 * we can just inject the {@code StatelessSession} directly,
+	 * and so in Quarkus we don't need the default constructor
+	 * at all.
+	 */
+	boolean needsDefaultConstructor() {
+		return jakartaDataRepository
+			&& !quarkusInjection
+			&& context.addDependentAnnotation();
+	}
+
 	private @Nullable ExecutableElement findSessionGetter(TypeElement type) {
 		if ( !hasAnnotation( type, ENTITY, MAPPED_SUPERCLASS, EMBEDDABLE )
 				|| isPanacheType( type ) ) {
diff --git a/tooling/metamodel-generator/src/main/java/org/hibernate/processor/annotation/RepositoryConstructor.java b/tooling/metamodel-generator/src/main/java/org/hibernate/processor/annotation/RepositoryConstructor.java
index 5523047706..cf285b697d 100644
--- a/tooling/metamodel-generator/src/main/java/org/hibernate/processor/annotation/RepositoryConstructor.java
+++ b/tooling/metamodel-generator/src/main/java/org/hibernate/processor/annotation/RepositoryConstructor.java
@@ -17,7 +17,7 @@ import org.hibernate.processor.util.Constants;
  * @author Gavin King
  */
 public class RepositoryConstructor implements MetaAttribute {
-	private final Metamodel annotationMetaEntity;
+	private final AnnotationMetaEntity annotationMetaEntity;
 	private final String constructorName;
 	private final String methodName;
 	private final String sessionTypeName;
@@ -30,7 +30,7 @@ public class RepositoryConstructor implements MetaAttribute {
 	private final boolean quarkusInjection;
 
 	public RepositoryConstructor(
-			Metamodel annotationMetaEntity,
+			AnnotationMetaEntity annotationMetaEntity,
 			String constructorName,
 			String methodName,
 			String sessionTypeName,
@@ -135,6 +135,11 @@ public class RepositoryConstructor implements MetaAttribute {
 		return declaration.toString();
 	}
 
+	/**
+	 * In Quarkus we use the Quarkus-specific {@code @PersistenceUnit}
+	 * CDI qualifier annotation to inject the {@code StatelessSession}
+	 * directly.
+	 */
 	private void qualifier(StringBuilder declaration) {
 		if ( addInjectAnnotation && quarkusInjection && dataStore != null ) {
 			declaration
@@ -146,13 +151,23 @@ public class RepositoryConstructor implements MetaAttribute {
 		}
 	}
 
+	/**
+	 * In Quarkus we inject the {@code StatelessSession}
+	 * directly via the constructor. But this doesn't work
+	 * in other CDI implementations, where we need to use
+	 * the JPA {@code @PersistenceUnit} annotation for
+	 * field injection of an {@code EntityManager}. In
+	 * that case, CDI will instantiate the repository via
+	 * a {@link DefaultConstructor default constructor},
+	 * so we don't need to mark this one {@code @Inject}.
+	 */
 	private void inject(StringBuilder declaration) {
 		// Jakarta Data repositories are instantiated
 		// via the default constructor, so in that
 		// case, this one is just for testing, unless
 		// we are in Quarkus where we can use
 		// constructor injection
-		if ( addInjectAnnotation && (!dataRepository || quarkusInjection) ) {
+		if ( addInjectAnnotation && !annotationMetaEntity.needsDefaultConstructor() ) {
 			declaration
 					.append('@')
 					.append(annotationMetaEntity.importType("jakarta.inject.Inject"))