core: trace object properties handles null properly (#1367)

Author: MykolaGolubyev

webtau-core/src/main/java/org/testingisdocumenting/webtau/data/converters/ObjectProperties.java

@@ -64,7 +64,9 @@ private List<Object> unwrapCollectionProperties(Collection<?> properties) {
     }
 
     private Object unwrappedProperties(Object v) {
-        if (v instanceof Collection) {
+        if (v == null) {
+            return null;
+        } if (v instanceof Collection) {
             return unwrapCollectionProperties((Collection<?>)v);
         } else if (v instanceof Map) {
             return unwrapMapProperties((Map<?, ?>) v);

webtau-core/src/test/groovy/org/testingisdocumenting/webtau/data/converters/ObjectPropertiesTest.groovy

@@ -108,4 +108,18 @@ class ObjectPropertiesTest {
         }
     }
 
+    @Test
+    void "table of objects with nulls"() {
+        def game1 = new GameConfig(null, Paths.get("/games/superA"))
+        def game2 = new GameConfig("duper game", null)
+
+        game1.registerAchievement("id1", "name", null)
+
+        runAndValidateOutput('[tracing] games\n' +
+                '  achievements                                         │ gameName     │ location     \n' +
+                '  [{"description": null, "id": "id1", "name": "name"}] │ null         │ /games/superA\n' +
+                '  []                                                   │ "duper game" │ null         ') {
+            trace("games", propertiesTable([game1, game2]))
+        }
+    }
 }