fix: Make sure the vector search feature is null-safe, too. (#3044)

This change introduces the necessary checks and annotations to make a build utilising Nullaway succeed:

```
./mvnw clean verify -Pnullaway
```

Also, `VectorSearchFragment` has been made `public`, as it is exposed via constructor of the public class `QueryFragmentsAndParameters`.

Signed-off-by: Michael Simons <michael@simons.ac>

Author: michael-simons

src/main/java/org/springframework/data/neo4j/core/Neo4jTemplate.java

@@ -449,7 +449,7 @@ public <T> T save(T instance) {
 		});
 	}
 
-	private <T> T saveImpl(T instance, Collection<PropertyFilter.ProjectedPath> includedProperties,
+	private <T> T saveImpl(T instance, @Nullable Collection<PropertyFilter.ProjectedPath> includedProperties,
 			@Nullable NestedRelationshipProcessingStateMachine stateMachine) {
 
 		if (stateMachine != null && stateMachine.hasProcessedValue(instance)) {
@@ -1489,12 +1489,7 @@ private Optional<Neo4jClient.RecordFetchSpec<T>> createFetchSpec() {
 					statement = nodesAndRelationshipsById.toStatement(entityMetaData);
 				}
 				else {
-					if (queryFragmentsAndParameters.hasVectorSearchFragment()) {
-						statement = queryFragments.toStatement(queryFragmentsAndParameters.getVectorSearchFragment());
-					}
-					else {
-						statement = queryFragments.toStatement();
-					}
+					statement = queryFragmentsAndParameters.toStatement();
 				}
 				cypherQuery = Neo4jTemplate.this.renderer.render(statement);
 				finalParameters = TemplateSupport.mergeParameters(statement, finalParameters);

src/main/java/org/springframework/data/neo4j/core/ReactiveNeo4jTemplate.java

@@ -469,13 +469,13 @@ <T, R> Flux<R> doSave(Iterable<R> instances, Class<T> domainType) {
 		});
 	}
 
-	private <T> Mono<T> saveImpl(T instance, Collection<PropertyFilter.ProjectedPath> includedProperties,
+	private <T> Mono<T> saveImpl(T instance, @Nullable Collection<PropertyFilter.ProjectedPath> includedProperties,
 			@Nullable NestedRelationshipProcessingStateMachine stateMachine) {
 		return saveImpl(instance, includedProperties, stateMachine, new HashSet<>());
 	}
 
 	@SuppressWarnings("deprecation")
-	private <T> Mono<T> saveImpl(T instance, Collection<PropertyFilter.ProjectedPath> includedProperties,
+	private <T> Mono<T> saveImpl(T instance, @Nullable Collection<PropertyFilter.ProjectedPath> includedProperties,
 			@Nullable NestedRelationshipProcessingStateMachine stateMachine, Collection<Object> knownRelationshipsIds) {
 
 		if (stateMachine != null && stateMachine.hasProcessedValue(instance)) {
@@ -1408,13 +1408,7 @@ public <T> Mono<ExecutableQuery<T>> toExecutableQuery(PreparedQuery<T> preparedQ
 							return new DefaultReactiveExecutableQuery<>(preparedQuery, fetchSpec);
 						});
 				}
-				Statement statement = null;
-				if (queryFragmentsAndParameters.hasVectorSearchFragment()) {
-					statement = queryFragments.toStatement(queryFragmentsAndParameters.getVectorSearchFragment());
-				}
-				else {
-					statement = queryFragments.toStatement();
-				}
+				Statement statement = queryFragmentsAndParameters.toStatement();
 				cypherQuery = this.renderer.render(statement);
 				finalParameters = TemplateSupport.mergeParameters(statement, finalParameters);
 			}

src/main/java/org/springframework/data/neo4j/core/TemplateSupport.java

@@ -137,10 +137,10 @@ else if (candidate != type) {
 		return candidate;
 	}
 
-	static PropertyFilter computeIncludePropertyPredicate(Collection<PropertyFilter.ProjectedPath> includedProperties,
-			NodeDescription<?> nodeDescription) {
+	static PropertyFilter computeIncludePropertyPredicate(
+			@Nullable Collection<PropertyFilter.ProjectedPath> includedProperties, NodeDescription<?> nodeDescription) {
 
-		return PropertyFilter.from(includedProperties, nodeDescription);
+		return PropertyFilter.from(Objects.requireNonNullElseGet(includedProperties, List::of), nodeDescription);
 	}
 
 	static void updateVersionPropertyIfPossible(Neo4jPersistentEntity<?> entityMetaData,
@@ -207,8 +207,8 @@ static Map<String, Object> mergeParameters(Statement statement, Map<String, Obje
 	 * @return a new binder function that only works on the included properties.
 	 */
 	static <T> FilteredBinderFunction<T> createAndApplyPropertyFilter(
-			Collection<PropertyFilter.ProjectedPath> includedProperties, Neo4jPersistentEntity<?> entityMetaData,
-			Function<T, Map<String, Object>> binderFunction) {
+			@Nullable Collection<PropertyFilter.ProjectedPath> includedProperties,
+			Neo4jPersistentEntity<?> entityMetaData, Function<T, Map<String, Object>> binderFunction) {
 
 		PropertyFilter includeProperty = TemplateSupport.computeIncludePropertyPredicate(includedProperties,
 				entityMetaData);

src/main/java/org/springframework/data/neo4j/repository/query/CypherQueryCreator.java

@@ -208,7 +208,7 @@ protected QueryFragmentsAndParameters complete(@Nullable Condition condition, So
 		if (this.keysetRequiresSort && theSort.isUnsorted()) {
 			throw new UnsupportedOperationException("Unsorted keyset based scrolling is not supported.");
 		}
-		if (this.queryMethod.hasVectorSearchAnnotation()) {
+		if (this.queryMethod.hasVectorSearchAnnotation() && this.vectorSearchParameter != null) {
 			var vectorSearchAnnotation = this.queryMethod.getVectorSearchAnnotation().orElseThrow();
 			var indexName = vectorSearchAnnotation.indexName();
 			var numberOfNodes = vectorSearchAnnotation.numberOfNodes();
@@ -219,9 +219,8 @@ protected QueryFragmentsAndParameters complete(@Nullable Condition condition, So
 			}
 			var vectorSearchFragment = new VectorSearchFragment(indexName, numberOfNodes,
 					(this.scoreParameter != null) ? this.scoreParameter.getValue() : null);
-			var queryFragmentsAndParameters = new QueryFragmentsAndParameters(this.nodeDescription, queryFragments,
-					vectorSearchFragment, convertedParameters, theSort);
-			return queryFragmentsAndParameters;
+			return new QueryFragmentsAndParameters(this.nodeDescription, queryFragments, vectorSearchFragment,
+					convertedParameters, theSort);
 		}
 		return new QueryFragmentsAndParameters(this.nodeDescription, queryFragments, convertedParameters, theSort);
 	}

src/main/java/org/springframework/data/neo4j/repository/query/QueryFragments.java

@@ -208,7 +208,7 @@ public Statement toStatement(VectorSearchFragment vectorSearchFragment) {
 			.with(Cypher.name("node").as(((Node) this.matchOn.get(0)).getRequiredSymbolicName().getValue()),
 					Cypher.name("score").as(Constants.NAME_OF_SCORE));
 
-		StatementBuilder.OngoingReadingWithoutWhere match = null;
+		StatementBuilder.OngoingReadingWithoutWhere match;
 		if (vectorSearchFragment.hasScore()) {
 			match = vectorSearch
 				.where(Cypher.raw(Constants.NAME_OF_SCORE)

src/main/java/org/springframework/data/neo4j/repository/query/QueryFragmentsAndParameters.java

@@ -33,6 +33,7 @@
 import org.neo4j.cypherdsl.core.PatternElement;
 import org.neo4j.cypherdsl.core.RelationshipPattern;
 import org.neo4j.cypherdsl.core.SortItem;
+import org.neo4j.cypherdsl.core.Statement;
 
 import org.springframework.data.domain.Example;
 import org.springframework.data.domain.KeysetScrollPosition;
@@ -63,6 +64,7 @@ public final class QueryFragmentsAndParameters {
 
 	private final QueryFragments queryFragments;
 
+	@Nullable
 	private final VectorSearchFragment vectorSearchFragment;
 
 	@Nullable
@@ -76,7 +78,7 @@ public final class QueryFragmentsAndParameters {
 	private NodeDescription<?> nodeDescription;
 
 	public QueryFragmentsAndParameters(@Nullable NodeDescription<?> nodeDescription, QueryFragments queryFragments,
-			VectorSearchFragment vectorSearchFragment, Map<String, Object> parameters, @Nullable Sort sort) {
+			@Nullable VectorSearchFragment vectorSearchFragment, Map<String, Object> parameters, @Nullable Sort sort) {
 		this.nodeDescription = nodeDescription;
 		this.queryFragments = queryFragments;
 		this.vectorSearchFragment = vectorSearchFragment;
@@ -402,10 +404,6 @@ public boolean hasVectorSearchFragment() {
 		return this.vectorSearchFragment != null;
 	}
 
-	public VectorSearchFragment getVectorSearchFragment() {
-		return this.vectorSearchFragment;
-	}
-
 	@Nullable public String getCypherQuery() {
 		return this.cypherQuery;
 	}
@@ -418,4 +416,11 @@ public Sort getSort() {
 		return this.sort;
 	}
 
+	public Statement toStatement() {
+		if (this.hasVectorSearchFragment()) {
+			return this.queryFragments.toStatement(Objects.requireNonNull(this.vectorSearchFragment));
+		}
+		return this.queryFragments.toStatement();
+	}
+
 }

src/main/java/org/springframework/data/neo4j/repository/query/VectorSearchFragment.java

@@ -25,7 +25,7 @@
  * @param numberOfNodes number of nodes to fetch from the index search
  * @param score score filter
  */
-record VectorSearchFragment(String indexName, int numberOfNodes, @Nullable Double score) {
+public record VectorSearchFragment(String indexName, int numberOfNodes, @Nullable Double score) {
 
 	boolean hasScore() {
 		return this.score != null;