Polishing.

Move auto index create lookup flag to dedicated method and add issue reference to tests.
Original Pull Request: #4275

spring-data-mongodb/src/main/java/org/springframework/data/mongodb/config/MappingMongoConverterParser.java

@@ -59,6 +59,7 @@ import org.springframework.data.mongodb.core.mapping.event.ValidatingMongoEventL
 import org.springframework.lang.Nullable;
 import org.springframework.util.Assert;
 import org.springframework.util.ClassUtils;
+import org.springframework.util.ObjectUtils;
 import org.springframework.util.StringUtils;
 import org.springframework.util.xml.DomUtils;
 import org.w3c.dom.Element;
@@ -94,8 +95,7 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 		String id = element.getAttribute(AbstractBeanDefinitionParser.ID_ATTRIBUTE);
 		id = StringUtils.hasText(id) ? id : DEFAULT_CONVERTER_BEAN_NAME;
 
-		String autoIndexCreation = element.getAttribute("auto-index-creation");
-		boolean autoIndexCreationEnabled = StringUtils.hasText(autoIndexCreation) && Boolean.parseBoolean(autoIndexCreation);
+		boolean autoIndexCreationEnabled = isAutoIndexCreationEnabled(element);
 
 		parserContext.pushContainingComponent(new CompositeComponentDefinition("Mapping Mongo Converter", element));
 
@@ -196,11 +196,33 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 		return new RuntimeBeanReference(validatorName);
 	}
 
+	private static boolean isAutoIndexCreationEnabled(Element element) {
+
+		String autoIndexCreation = element.getAttribute("auto-index-creation");
+		return StringUtils.hasText(autoIndexCreation) && Boolean.parseBoolean(autoIndexCreation);
+	}
+
+	/**
+	 * Create and register the {@link BeanDefinition} for a {@link MongoMappingContext} if not explicitly referenced by a
+	 * given {@literal mapping-context-ref} {@link Element#getAttribute(String) attribuite}.
+	 * 
+	 * @return the mapping context bean name.
+	 * @deprecated since 4.3. Use
+	 *             {@link #potentiallyCreateMappingContext(Element, ParserContext, BeanDefinition, String, boolean)}
+	 *             instead.
+	 */
+	@Deprecated(since = "4.3", forRemoval = true)
 	public static String potentiallyCreateMappingContext(Element element, ParserContext parserContext,
 			@Nullable BeanDefinition conversionsDefinition, @Nullable String converterId) {
 		return potentiallyCreateMappingContext(element, parserContext, conversionsDefinition, converterId, false);
 	}
 
+	/**
+	 * Create and register the {@link BeanDefinition} for a {@link MongoMappingContext} if not explicitly referenced by a
+	 * given {@literal mapping-context-ref} {@link Element#getAttribute(String) attribuite}.
+	 * 
+	 * @return the mapping context bean name.
+	 */
 	public static String potentiallyCreateMappingContext(Element element, ParserContext parserContext,
 			@Nullable BeanDefinition conversionsDefinition, @Nullable String converterId, boolean autoIndexCreation) {
 
@@ -280,8 +302,10 @@ public class MappingMongoConverterParser implements BeanDefinitionParser {
 			ManagedList<BeanMetadataElement> converterBeans = new ManagedList<>();
 			List<Element> converterElements = DomUtils.getChildElementsByTagName(customerConvertersElement, "converter");
 
-			for (Element listenerElement : converterElements) {
-				converterBeans.add(parseConverter(listenerElement, parserContext));
+			if (!ObjectUtils.isEmpty(converterElements)) {
+				for (Element listenerElement : converterElements) {
+					converterBeans.add(parseConverter(listenerElement, parserContext));
+				}
 			}
 
 			// Scan for Converter and GenericConverter beans in the given base-package

spring-data-mongodb/src/test/java/org/springframework/data/mongodb/config/MappingMongoConverterParserIntegrationTests.java

@@ -22,7 +22,6 @@ import java.util.Set;
 
 import org.bson.Document;
 import org.junit.jupiter.api.Test;
-
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.beans.factory.config.BeanReference;
 import org.springframework.beans.factory.parsing.BeanDefinitionParsingException;
@@ -63,22 +62,24 @@ public class MappingMongoConverterParserIntegrationTests {
 		factory.getBean("converter");
 	}
 
-	@Test
+	@Test // GH-4275
+	void defaultsToFalseForAutoIndexCreation() {
+
+		loadValidConfiguration();
+		MongoMappingContext mongoMappingContext = factory.getBean("converter.mongoMappingContext",
+				MongoMappingContext.class);
+		assertThat(mongoMappingContext.isAutoIndexCreation()).isFalse();
+	}
+
+	@Test // GH-4275
 	void allowsToOverrideAutoIndexCreation() {
 
 		loadValidConfiguration();
-		MongoMappingContext mongoMappingContext = factory.getBean("autoIndexCreationConverter.mongoMappingContext", MongoMappingContext.class);
+		MongoMappingContext mongoMappingContext = factory.getBean("autoIndexCreationConverter.mongoMappingContext",
+				MongoMappingContext.class);
 		assertThat(mongoMappingContext.isAutoIndexCreation()).isTrue();
 	}
 
-	@Test
-	void testDefaultValueForAutoIndexCreation() {
-
-		loadValidConfiguration();
-		MongoMappingContext mongoMappingContext = factory.getBean("converter.mongoMappingContext", MongoMappingContext.class);
-		assertThat(mongoMappingContext.isAutoIndexCreation()).isFalse();
-	}
-
 	@Test // DATAMONGO-725
 	void hasCustomTypeMapper() {