HSEARCH-5158 Return non-null mass indexer from a standalone search scope

Author: marko-bekhta

integrationtest/mapper/pojo-base/src/test/java/org/hibernate/search/integrationtest/mapper/pojo/massindexing/MassIndexingBaseIT.java

@@ -114,6 +114,51 @@ void defaultMassIndexerStartAndWait() throws Exception {
 		backendMock.verifyExpectationsMet();
 	}
 
+	@Test
+	void defaultMassIndexerFromScopeStartAndWait() throws Exception {
+		try ( SearchSession searchSession = mapping.createSession() ) {
+			MassIndexer indexer = searchSession.scope( Book.class ).massIndexer( (Object) null )
+					// Simulate passing information to connect to a DB, ...
+					.context( StubLoadingContext.class, loadingContext );
+
+			// add operations on indexes can follow any random order,
+			// since they are executed by different threads
+			backendMock.expectWorks(
+					Book.NAME, DocumentCommitStrategy.NONE, DocumentRefreshStrategy.NONE
+			)
+					.add( "1", b -> b
+							.field( "title", TITLE_1 )
+							.field( "author", AUTHOR_1 )
+					)
+					.add( "2", b -> b
+							.field( "title", TITLE_2 )
+							.field( "author", AUTHOR_2 )
+					)
+					.add( "3", b -> b
+							.field( "title", TITLE_3 )
+							.field( "author", AUTHOR_3 )
+					);
+
+			// purgeAtStart and mergeSegmentsAfterPurge are enabled by default,
+			// so we expect 1 purge, 1 mergeSegments and 1 flush calls in this order:
+			backendMock.expectIndexScaleWorks( Book.NAME, searchSession.tenantIdentifierValue() )
+					.purge()
+					.mergeSegments()
+					.flush()
+					.refresh();
+
+			try {
+				indexer.startAndWait();
+			}
+			catch (InterruptedException e) {
+				fail( "Unexpected InterruptedException: " + e.getMessage() );
+			}
+
+		}
+
+		backendMock.verifyExpectationsMet();
+	}
+
 	@Test
 	void dropAndCreateSchemaOnStart() {
 		try ( SearchSession searchSession = mapping.createSession() ) {

mapper/pojo-standalone/src/main/java/org/hibernate/search/mapper/pojo/standalone/scope/impl/SearchScopeImpl.java

@@ -6,6 +6,8 @@
  */
 package org.hibernate.search.mapper.pojo.standalone.scope.impl;
 
+import static org.hibernate.search.util.common.impl.CollectionHelper.asSetIgnoreNull;
+
 import java.util.Collections;
 import java.util.Set;
 import java.util.stream.Collectors;
@@ -33,7 +35,6 @@
 import org.hibernate.search.mapper.pojo.standalone.tenancy.impl.TenancyConfiguration;
 import org.hibernate.search.mapper.pojo.standalone.work.SearchWorkspace;
 import org.hibernate.search.mapper.pojo.standalone.work.impl.SearchWorkspaceImpl;
-import org.hibernate.search.util.common.impl.Contracts;
 
 public class SearchScopeImpl<E> implements SearchScope<E> {
 
@@ -118,13 +119,12 @@ public MassIndexer massIndexer() {
 	@Override
 	@SuppressWarnings("removal")
 	public MassIndexer massIndexer(String tenantId) {
-		Contracts.assertNotNull( tenantId, "tenant identifier" );
-		return massIndexer( Collections.singleton( tenantId ) );
+		return massIndexer( (Object) tenantId );
 	}
 
 	@Override
 	public MassIndexer massIndexer(Object tenantId) {
-		return null;
+		return massIndexer( asSetIgnoreNull( tenantId ) );
 	}
 
 	@Override