#57 - Have MutableAnnotationTarget#applyAnnotationUsage operate as get-or-make

Author: sebersole

src/main/java/org/hibernate/models/spi/MutableAnnotationTarget.java

@@ -27,7 +27,8 @@ public interface MutableAnnotationTarget extends AnnotationTarget {
 	<X extends Annotation> void addAnnotationUsage(AnnotationUsage<X> annotationUsage);
 
 	/**
-	 * Creates a usage and adds it to this target.
+	 * Applies a usage of the given {@code annotationType} to this target.  Will return
+	 * an existing usage, if one, or create a new usage.
 	 */
 	default <A extends Annotation> MutableAnnotationUsage<A> applyAnnotationUsage(
 			AnnotationDescriptor<A> annotationType,
@@ -36,12 +37,22 @@ default <A extends Annotation> MutableAnnotationUsage<A> applyAnnotationUsage(
 	}
 
 	/**
-	 * Creates a usage and adds it to this target, allowing for configuration of the created usage
+	 * Applies a usage of the given {@code annotationType} to this target, allowing
+	 * for configuration of the applied usage.  Will return an existing usage, if one,
+	 * or create a new usage.
 	 */
 	default <A extends Annotation> MutableAnnotationUsage<A> applyAnnotationUsage(
 			AnnotationDescriptor<A> annotationType,
 			Consumer<MutableAnnotationUsage<A>> configuration,
 			SourceModelBuildingContext buildingContext) {
+		final MutableAnnotationUsage<A> existing = (MutableAnnotationUsage<A>) getAnnotationUsage( annotationType );
+		if ( existing != null ) {
+			if ( configuration != null ) {
+				configuration.accept( existing );
+			}
+			return existing;
+		}
+
 		final MutableAnnotationUsage<A> usage = annotationType.createUsage( this, configuration, buildingContext );
 		addAnnotationUsage( usage );
 		return usage;

src/test/java/org/hibernate/models/dynamic/SimpleDynamicModelTests.java

@@ -50,14 +50,32 @@ void testSimpleBasics() {
 				"TheEntity",
 				name -> new DynamicClassDetails( name, buildingContext )
 		);
-		entityDetails.applyAnnotationUsage( JpaAnnotations.ENTITY, buildingContext );
+		final MutableAnnotationUsage<Entity> created = entityDetails.applyAnnotationUsage(
+				JpaAnnotations.ENTITY,
+				buildingContext
+		);
+		final MutableAnnotationUsage<Entity> preExisting = entityDetails.applyAnnotationUsage(
+				JpaAnnotations.ENTITY,
+				buildingContext
+		);
+		assertThat( created ).isSameAs( preExisting );
 
 		entityDetails.applyAttribute(
 				"id",
 				integerTypeDetails,
 				false,
 				false,
-				fieldDetails -> fieldDetails.applyAnnotationUsage( JpaAnnotations.ID, buildingContext ),
+				fieldDetails -> {
+					final MutableAnnotationUsage<Id> first = fieldDetails.applyAnnotationUsage(
+							JpaAnnotations.ID,
+							buildingContext
+					);
+					final MutableAnnotationUsage<Id> second = fieldDetails.applyAnnotationUsage(
+							JpaAnnotations.ID,
+							buildingContext
+					);
+					assertThat( first ).isSameAs( second );
+				},
 				buildingContext
 		);