Fix NPE from trailing comma in module.txt dependencies

gestalt-module/src/main/java/org/terasology/gestalt/module/ModuleMetadataJsonAdapter.java

@@ -42,6 +42,7 @@
 import java.lang.reflect.Type;
 import java.util.List;
 import java.util.Map;
+import java.util.Objects;
 import java.util.Set;
 
 /**
@@ -183,7 +184,12 @@ public ModuleMetadata deserialize(JsonElement json, Type typeOfT, JsonDeserializ
                         metadata.setDescription(context.<I18nMap>deserialize(entry.getValue(), I18nMap.class));
                         break;
                     case ModuleMetadata.DEPENDENCIES:
-                        metadata.getDependencies().addAll((List<DependencyInfo>) context.deserialize(entry.getValue(), DEPENDENCY_LIST_TYPE));
+                        // Trailing comma -> Gson emits a phantom null element; strip it (#133).
+                        List<DependencyInfo> dependencyInfos = context.deserialize(entry.getValue(), DEPENDENCY_LIST_TYPE);
+                        if (dependencyInfos != null) {
+                            dependencyInfos.removeIf(Objects::isNull);
+                            metadata.getDependencies().addAll(dependencyInfos);
+                        }
                         break;
                     case ModuleMetadata.REQUIRED_PERMISSIONS:
                         metadata.getRequiredPermissions().addAll((Set<String>) context.deserialize(entry.getValue(), STRING_SET_TYPE));

gestalt-module/src/test/java/org/terasology/gestalt/module/ModuleMetadataJsonAdapterTest.java

@@ -66,4 +66,22 @@ public void testReadWrite() {
 
         Assert.assertEquals(meta, parsedMeta);
     }
+
+    @Test
+    public void testTrailingCommaInDependenciesDoesNotProduceNullElement() {
+        // Gson's lenient reader accepts this invalid JSON (trailing comma) and would
+        // otherwise leave a null element in the dependencies list. See #133.
+        String json = "{"
+                + "\"id\": \"ModuleNameId\","
+                + "\"dependencies\": ["
+                + "{\"id\": \"myDependency\", \"minVersion\": \"1.0.0\", \"maxVersion\": \"2.0.0\"},"
+                + "]"
+                + "}";
+
+        ModuleMetadataJsonAdapter adapter = new ModuleMetadataJsonAdapter();
+        ModuleMetadata parsedMeta = adapter.read(new StringReader(json));
+
+        Assert.assertEquals(1, parsedMeta.getDependencies().size());
+        Assert.assertFalse(parsedMeta.getDependencies().contains(null));
+    }
 }