Remove @Nullable from VectorStore similaritySearch (#3613)

The VectorStore#similaritySearch methods never return null, but there's
a data flow issue in AbstractObservationVectorStore caused by Micrometer's
Observation#observe being marked as @nullable. The returned value is
actually controlled by Spring AI's supplier, which never returns null.

Fixes #3613
Auto-cherry-pick to 1.0.x

Signed-off-by: Filip Hrisafov <[email protected]>

Author: filiphr

spring-ai-vector-store/src/main/java/org/springframework/ai/vectorstore/VectorStore.java

@@ -27,7 +27,6 @@
 import org.springframework.ai.vectorstore.filter.Filter;
 import org.springframework.ai.vectorstore.observation.DefaultVectorStoreObservationConvention;
 import org.springframework.ai.vectorstore.observation.VectorStoreObservationConvention;
-import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 
 /**
@@ -91,7 +90,6 @@ default void delete(String filterExpression) {
 	 * topK, similarity threshold and metadata filter expressions.
 	 * @return Returns documents th match the query request conditions.
 	 */
-	@Nullable
 	List<Document> similaritySearch(SearchRequest request);
 
 	/**
@@ -101,7 +99,6 @@ default void delete(String filterExpression) {
 	 * @return Returns a list of documents that have embeddings similar to the query text
 	 * embedding.
 	 */
-	@Nullable
 	default List<Document> similaritySearch(String query) {
 		return this.similaritySearch(SearchRequest.builder().query(query).build());
 	}

spring-ai-vector-store/src/main/java/org/springframework/ai/vectorstore/observation/AbstractObservationVectorStore.java

@@ -111,7 +111,9 @@ public void delete(Filter.Expression filterExpression) {
 	}
 
 	@Override
-	@Nullable
+	// Micrometer Observation#observe returns the value of the Supplier, which is never
+	// null
+	@SuppressWarnings("DataFlowIssue")
 	public List<Document> similaritySearch(SearchRequest request) {
 
 		VectorStoreObservationContext searchObservationContext = this

vector-stores/spring-ai-azure-cosmos-db-store/src/main/java/org/springframework/ai/vectorstore/cosmosdb/CosmosDBVectorStore.java

@@ -434,15 +434,13 @@ public List<Document> doSimilaritySearch(SearchRequest request) {
 			}
 
 			// Convert JsonNode to Document
-			List<Document> docs = documents.stream()
+			return documents.stream()
 				.map(doc -> Document.builder()
 					.id(doc.get("id").asText())
 					.text(doc.get("content").asText())
 					.metadata(docFields)
 					.build())
 				.collect(Collectors.toList());
-
-			return docs != null ? docs : List.of();
 		}
 		catch (Exception e) {
 			logger.error("Error during similarity search: {}", e.getMessage());

vector-stores/spring-ai-chroma-store/src/main/java/org/springframework/ai/chroma/vectorstore/ChromaVectorStore.java

@@ -45,7 +45,6 @@
 import org.springframework.ai.vectorstore.observation.AbstractObservationVectorStore;
 import org.springframework.ai.vectorstore.observation.VectorStoreObservationContext;
 import org.springframework.beans.factory.InitializingBean;
-import org.springframework.lang.NonNull;
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.CollectionUtils;
@@ -148,7 +147,7 @@ public void afterPropertiesSet() throws Exception {
 	}
 
 	@Override
-	public void doAdd(@NonNull List<Document> documents) {
+	public void doAdd(List<Document> documents) {
 		Assert.notNull(documents, "Documents must not be null");
 		if (CollectionUtils.isEmpty(documents)) {
 			return;
@@ -202,8 +201,7 @@ protected void doDelete(Filter.Expression expression) {
 	}
 
 	@Override
-	@NonNull
-	public List<Document> doSimilaritySearch(@NonNull SearchRequest request) {
+	public List<Document> doSimilaritySearch(SearchRequest request) {
 
 		String query = request.getQuery();
 		Assert.notNull(query, "Query string must not be null");

vector-stores/spring-ai-gemfire-store/src/main/java/org/springframework/ai/vectorstore/gemfire/GemFireVectorStore.java

@@ -243,7 +243,6 @@ public void doDelete(List<String> idList) {
 	}
 
 	@Override
-	@Nullable
 	public List<Document> doSimilaritySearch(SearchRequest request) {
 		if (request.hasFilterExpression()) {
 			throw new UnsupportedOperationException("GemFire currently does not support metadata filter expressions.");