Polish 'Add origin support for empty YAML list and map'

See gh-21704

spring-boot-project/spring-boot/src/main/java/org/springframework/boot/env/OriginTrackedYamlLoader.java

@@ -105,15 +105,15 @@ class OriginTrackedYamlLoader extends YamlProcessor {
 
 		@Override
 		protected Object constructObject(Node node) {
+			if (node instanceof CollectionNode && ((CollectionNode<?>) node).getValue().isEmpty()) {
+				return constructTrackedObject(node, super.constructObject(node));
+			}
 			if (node instanceof ScalarNode) {
 				if (!(node instanceof KeyScalarNode)) {
 					return constructTrackedObject(node, super.constructObject(node));
 				}
 			}
-			else if (node instanceof CollectionNode && ((CollectionNode<?>) node).getValue().isEmpty()) {
-				return constructTrackedObject(node, super.constructObject(node));
-			}
-			else if (node instanceof MappingNode) {
+			if (node instanceof MappingNode) {
 				replaceMappingNodeKeys((MappingNode) node);
 			}
 			return super.constructObject(node);

spring-boot-project/spring-boot/src/test/java/org/springframework/boot/env/OriginTrackedYamlLoaderTests.java

@@ -125,8 +125,8 @@ class OriginTrackedYamlLoaderTests {
 	void processEmptyListAndMap() {
 		OriginTrackedValue emptymap = getValue("emptymap");
 		OriginTrackedValue emptylist = getValue("emptylist");
-		assertThat(emptymap.getValue()).isEqualTo(Collections.EMPTY_MAP);
-		assertThat(emptylist.getValue()).isEqualTo(Collections.EMPTY_LIST);
+		assertThat(emptymap.getValue()).isEqualTo(Collections.emptyMap());
+		assertThat(emptylist.getValue()).isEqualTo(Collections.emptyList());
 	}
 
 	@Test