Unity-Technologies/UnityCsReference · error · ArgumentException

plainGameObjects has no objects

Error message

plainGameObjects has no objects

What it means

PrefabUtility.ConvertToPrefabInstances throws an ArgumentException when plainGameObjects is an empty array. The API requires at least one GameObject to operate on; an empty array is meaningless for prefab conversion.

Source

Thrown at Editor/Mono/Prefabs/PrefabUtility.cs:2394

            }
        }

        public static void ConvertToPrefabInstance(GameObject plainGameObject, GameObject prefabAssetRoot, ConvertToPrefabInstanceSettings settings, InteractionMode mode)
        {
            ThrowIfInvalidArgumentsForConvertToPrefabInstance(plainGameObject, prefabAssetRoot, true, mode);

            ConvertToPrefabInstance_NoInputValidation(plainGameObject, prefabAssetRoot, settings, mode);

            EditorUtility.ForceRebuildInspectors();
        }

        public static void ConvertToPrefabInstances(GameObject[] plainGameObjects, GameObject prefabAssetRoot, ConvertToPrefabInstanceSettings settings, InteractionMode mode)
        {
            if (plainGameObjects == null)
                throw new ArgumentNullException(nameof(plainGameObjects));

            if (plainGameObjects.Length == 0)
                throw new ArgumentException(nameof(plainGameObjects) + " has no objects");

            foreach(var go in plainGameObjects)
                if (go == null)
                    throw new ArgumentException(nameof(plainGameObjects) + " has a null GameObject");

            if (settings == null)
                throw new ArgumentNullException(nameof(settings));

            ThrowIfInvalidAssetForReplacePrefabInstance(prefabAssetRoot, mode);

            var topLevelGameObjects = GetTopLevelGameObjects(plainGameObjects);
            foreach (var go in topLevelGameObjects)
                ThrowIfInvalidArgumentsForConvertToPrefabInstance(go, prefabAssetRoot, false, mode);

            foreach (var go in topLevelGameObjects)
                ConvertToPrefabInstance_NoInputValidation(go, prefabAssetRoot, settings, mode);

            EditorUtility.ForceRebuildInspectors();

View on GitHub (pinned to 225b0fbdb5)

Solutions

1. Check plainGameObjects.Length > 0 before calling the API.
2. Guard with early return: if (gos.Length == 0) return;
3. Use Selection.gameObjects filtered to valid candidates and verify count before proceeding.

Example fix

// before
PrefabUtility.ConvertToPrefabInstances(new GameObject[0], root, settings, InteractionMode.AutomatedAction);
// after
if (gos != null && gos.Length > 0)
    PrefabUtility.ConvertToPrefabInstances(gos, root, settings, InteractionMode.AutomatedAction);

if (plainGameObjects == null || plainGameObjects.Length == 0)
    return;
PrefabUtility.ConvertToPrefabInstances(plainGameObjects, root, settings, mode);

static bool HasObjects(GameObject[] arr) => arr != null && arr.Length > 0;

When it happens

Trigger: Calling ConvertToPrefabInstances with a zero-length GameObject[] (e.g., new GameObject[0], Array.Empty<GameObject>(), or an empty selection).

Common situations: User selected nothing in the Hierarchy, a filter returned zero results, or a bulk-operation pipeline ran with an empty input set.

Related errors

• UnpackPrefabInstance must be called with a Prefab instance.
• UnpackPrefabInstance must be called with a root Prefab insta
• Scene path cannot be null or empty.
• Path {scenePath} is not a scene path. Must end with .unity e
• No material targets provided

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/78d080a6937bace4. Report an issue: GitHub.