From 547a1df4bd780ce6fe9e27333c474b989bc0fd54 Mon Sep 17 00:00:00 2001
From: Gerrit Meier <meistermeier@gmail.com>
Date: Tue, 3 Nov 2020 08:12:06 +0100
Subject: [PATCH] DATAGRAPH-1420 - Check for TargetNode in
 RelationshipProperties.

---
 .../DefaultNeo4jPersistentProperty.java       |  8 +++-
 .../DefaultNeo4jPersistentEntityTest.java     | 43 +++++++++++++++++++
 2 files changed, 49 insertions(+), 2 deletions(-)

diff --git a/src/main/java/org/springframework/data/neo4j/core/mapping/DefaultNeo4jPersistentProperty.java b/src/main/java/org/springframework/data/neo4j/core/mapping/DefaultNeo4jPersistentProperty.java
index 8cd38209e..45c60bda8 100644
--- a/src/main/java/org/springframework/data/neo4j/core/mapping/DefaultNeo4jPersistentProperty.java
+++ b/src/main/java/org/springframework/data/neo4j/core/mapping/DefaultNeo4jPersistentProperty.java
@@ -154,8 +154,12 @@ final class DefaultNeo4jPersistentProperty extends AnnotationBasedPersistentProp
 
 	@NonNull
 	private Class<?> getRelationshipPropertiesTargetType(Class<?> relationshipPropertiesType) {
-		return this.mappingContext.getPersistentEntity(relationshipPropertiesType)
-				.getPersistentProperty(TargetNode.class).getType();
+		Neo4jPersistentProperty persistentProperty = this.mappingContext.getPersistentEntity(relationshipPropertiesType)
+				.getPersistentProperty(TargetNode.class);
+		if (persistentProperty == null) {
+			throw new MappingException("Missing @TargetNode declaration in " + relationshipPropertiesType);
+		}
+		return persistentProperty.getType();
 	}
 
 	@Override
diff --git a/src/test/java/org/springframework/data/neo4j/core/mapping/DefaultNeo4jPersistentEntityTest.java b/src/test/java/org/springframework/data/neo4j/core/mapping/DefaultNeo4jPersistentEntityTest.java
index a356bc025..bc27f0eab 100644
--- a/src/test/java/org/springframework/data/neo4j/core/mapping/DefaultNeo4jPersistentEntityTest.java
+++ b/src/test/java/org/springframework/data/neo4j/core/mapping/DefaultNeo4jPersistentEntityTest.java
@@ -16,6 +16,7 @@
 package org.springframework.data.neo4j.core.mapping;
 
 import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatExceptionOfType;
 import static org.assertj.core.api.Assertions.assertThatIllegalStateException;
 
 import java.util.Arrays;
@@ -28,12 +29,15 @@ import org.junit.jupiter.api.Nested;
 import org.junit.jupiter.api.Test;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.ValueSource;
+import org.springframework.data.mapping.MappingException;
 import org.springframework.data.neo4j.core.schema.DynamicLabels;
 import org.springframework.data.neo4j.core.schema.GeneratedValue;
 import org.springframework.data.neo4j.core.schema.Id;
 import org.springframework.data.neo4j.core.schema.Node;
 import org.springframework.data.neo4j.core.schema.Property;
 import org.springframework.data.neo4j.core.schema.Relationship;
+import org.springframework.data.neo4j.core.schema.RelationshipProperties;
+import org.springframework.data.neo4j.core.schema.TargetNode;
 
 /**
  * @author Gerrit Meier
@@ -89,6 +93,23 @@ class DefaultNeo4jPersistentEntityTest {
 			schema.setInitialEntitySet(new HashSet<>(Arrays.asList(entityToTest)));
 			assertThatIllegalStateException().isThrownBy(() -> schema.initialize()).withMessageMatching(expectedMessage);
 		}
+
+		@Test // DATAGRAPH-1420
+		void doesNotFailOnCorrectRelationshipProperties() {
+			Neo4jPersistentEntity<?> persistentEntity = new Neo4jMappingContext()
+					.getPersistentEntity(EntityWithCorrectRelationshipProperties.class);
+
+			assertThat(persistentEntity).isNotNull();
+		}
+
+		@Test // DATAGRAPH-1420
+		void doesFailOnRelationshipPropertiesWithMissingTargetNode() {
+
+			assertThatExceptionOfType(MappingException.class)
+					.isThrownBy(() -> new Neo4jMappingContext()
+							.getPersistentEntity(EntityWithInCorrectRelationshipProperties.class))
+					.withMessageContaining("Missing @TargetNode declaration in");
+		}
 	}
 
 	@Nested
@@ -391,4 +412,26 @@ class DefaultNeo4jPersistentEntityTest {
 
 		private Map<String, List<Neo4jMappingContextTest.BikeNode>> bikes2;
 	}
+
+	static class EntityWithCorrectRelationshipProperties {
+		@Id private String id;
+		@Relationship HasTargetNodeRelationshipProperties rel;
+	}
+
+	static class EntityWithInCorrectRelationshipProperties {
+		@Id private String id;
+		@Relationship HasNoTargetNodeRelationshipProperties rel;
+	}
+
+	@RelationshipProperties
+	static class HasTargetNodeRelationshipProperties {
+
+		@TargetNode
+		EntityWithExplicitPrimaryLabel entity;
+	}
+
+	@RelationshipProperties
+	static class HasNoTargetNodeRelationshipProperties {
+
+	}
 }