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dsarnoclaude
dsarno
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claude
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Add create_child parameter to manage_prefabs modify_contents (#646)
* Add create_child parameter to manage_prefabs modify_contents Enables adding child GameObjects to existing prefabs via headless editing. Supports single object or array for batch creation in one save operation. Features: - Create children with primitive types (Cube, Sphere, etc.) - Set position, rotation, scale on new children - Add components to children - Specify parent within prefab hierarchy for nested children - Set tag, layer, and active state Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> * Address code review feedback for create_child validation - Fix type hint to `tuple[dict | None, str | None]` to match actual returns - Add explicit dict validation with clear error message including actual type - Error on invalid component entries instead of silently ignoring them - Return ErrorResponse for invalid tag/layer instead of just logging warnings Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> * Add unit tests for create_child prefab functionality Tests cover: - Single child with primitive type - Empty GameObject (no primitive_type) - Multiple children from array (batch creation) - Nested parenting within prefab - Error handling for invalid inputs Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com> --------- Co-authored-by: Claude Opus 4.5 <noreply@anthropic.com>
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‎MCPForUnity/Editor/Tools/Prefabs/ManagePrefabs.cs‎

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Original file line numberDiff line numberDiff line change
@@ -723,9 +723,188 @@ private static (bool modified, ErrorResponse error) ApplyModificationsToPrefabOb
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}
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}
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// Create child GameObjects (supports single object or array)
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JToken createChildToken = @params["createChild"] ?? @params["create_child"];
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if (createChildToken != null)
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{
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// Handle array of children
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if (createChildToken is JArray childArray)
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{
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foreach (var childToken in childArray)
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{
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var childResult = CreateSingleChildInPrefab(childToken, targetGo, prefabRoot);
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if (childResult.error != null)
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{
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return (false, childResult.error);
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}
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if (childResult.created)
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{
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modified = true;
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}
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}
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}
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else
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{
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// Handle single child object
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var childResult = CreateSingleChildInPrefab(createChildToken, targetGo, prefabRoot);
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if (childResult.error != null)
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{
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return (false, childResult.error);
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}
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if (childResult.created)
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{
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modified = true;
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}
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}
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}
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return (modified, null);
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}
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/// <summary>
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/// Creates a single child GameObject within the prefab contents.
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/// </summary>
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private static (bool created, ErrorResponse error) CreateSingleChildInPrefab(JToken createChildToken, GameObject defaultParent, GameObject prefabRoot)
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{
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JObject childParams;
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if (createChildToken is JObject obj)
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{
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childParams = obj;
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}
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else
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{
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return (false, new ErrorResponse("'create_child' must be an object with child properties."));
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}
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// Required: name
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string childName = childParams["name"]?.ToString();
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if (string.IsNullOrEmpty(childName))
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{
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return (false, new ErrorResponse("'create_child.name' is required."));
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}
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// Optional: parent (defaults to the target object)
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string parentName = childParams["parent"]?.ToString();
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Transform parentTransform = defaultParent.transform;
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if (!string.IsNullOrEmpty(parentName))
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{
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GameObject parentGo = FindInPrefabContents(prefabRoot, parentName);
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if (parentGo == null)
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{
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return (false, new ErrorResponse($"Parent '{parentName}' not found in prefab for create_child."));
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}
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parentTransform = parentGo.transform;
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}
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// Create the GameObject
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GameObject newChild;
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string primitiveType = childParams["primitiveType"]?.ToString() ?? childParams["primitive_type"]?.ToString();
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if (!string.IsNullOrEmpty(primitiveType))
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{
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try
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{
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PrimitiveType type = (PrimitiveType)Enum.Parse(typeof(PrimitiveType), primitiveType, true);
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newChild = GameObject.CreatePrimitive(type);
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newChild.name = childName;
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}
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catch (ArgumentException)
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{
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return (false, new ErrorResponse($"Invalid primitive type: '{primitiveType}'. Valid types: {string.Join(", ", Enum.GetNames(typeof(PrimitiveType)))}"));
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}
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}
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else
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{
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newChild = new GameObject(childName);
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}
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// Set parent
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newChild.transform.SetParent(parentTransform, false);
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// Apply transform properties
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Vector3? position = VectorParsing.ParseVector3(childParams["position"]);
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Vector3? rotation = VectorParsing.ParseVector3(childParams["rotation"]);
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Vector3? scale = VectorParsing.ParseVector3(childParams["scale"]);
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if (position.HasValue)
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{
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newChild.transform.localPosition = position.Value;
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}
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if (rotation.HasValue)
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{
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newChild.transform.localEulerAngles = rotation.Value;
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}
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if (scale.HasValue)
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{
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newChild.transform.localScale = scale.Value;
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}
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// Add components
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JArray componentsToAdd = childParams["componentsToAdd"] as JArray ?? childParams["components_to_add"] as JArray;
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if (componentsToAdd != null)
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{
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for (int i = 0; i < componentsToAdd.Count; i++)
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{
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var compToken = componentsToAdd[i];
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string typeName = compToken.Type == JTokenType.String
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? compToken.ToString()
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: (compToken as JObject)?["typeName"]?.ToString();
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if (string.IsNullOrEmpty(typeName))
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{
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// Clean up partially created child
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UnityEngine.Object.DestroyImmediate(newChild);
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return (false, new ErrorResponse($"create_child.components_to_add[{i}] must be a string or object with 'typeName' field, got {compToken.Type}"));
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}
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if (!ComponentResolver.TryResolve(typeName, out Type componentType, out string error))
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{
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// Clean up partially created child
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UnityEngine.Object.DestroyImmediate(newChild);
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return (false, new ErrorResponse($"Component type '{typeName}' not found for create_child: {error}"));
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}
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newChild.AddComponent(componentType);
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}
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}
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// Set tag if specified
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string tag = childParams["tag"]?.ToString();
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if (!string.IsNullOrEmpty(tag))
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{
873+
try
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{
875+
newChild.tag = tag;
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}
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catch (Exception ex)
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{
879+
UnityEngine.Object.DestroyImmediate(newChild);
880+
return (false, new ErrorResponse($"Failed to set tag '{tag}' on child '{childName}': {ex.Message}"));
881+
}
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}
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// Set layer if specified
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string layerName = childParams["layer"]?.ToString();
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if (!string.IsNullOrEmpty(layerName))
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{
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int layerId = LayerMask.NameToLayer(layerName);
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if (layerId == -1)
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{
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UnityEngine.Object.DestroyImmediate(newChild);
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return (false, new ErrorResponse($"Invalid layer '{layerName}' for child '{childName}'. Use a valid layer name."));
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}
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newChild.layer = layerId;
895+
}
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897+
// Set active state
898+
bool? setActive = childParams["setActive"]?.ToObject<bool?>() ?? childParams["set_active"]?.ToObject<bool?>();
899+
if (setActive.HasValue)
900+
{
901+
newChild.SetActive(setActive.Value);
902+
}
903+
904+
McpLog.Info($"[ManagePrefabs] Created child '{childName}' under '{parentTransform.name}' in prefab.");
905+
return (true, null);
906+
}
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729908
#endregion
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731910
#region Hierarchy Builder

‎Server/src/services/tools/manage_prefabs.py‎

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Original file line numberDiff line numberDiff line change
@@ -25,6 +25,10 @@
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"Manages Unity Prefab assets via headless operations (no UI, no prefab stages). "
2626
"Actions: get_info, get_hierarchy, create_from_gameobject, modify_contents. "
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"Use modify_contents for headless prefab editing - ideal for automated workflows. "
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"Use create_child parameter with modify_contents to add child GameObjects to a prefab "
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"(single object or array for batch creation in one save). "
30+
"Example: create_child=[{\"name\": \"Child1\", \"primitive_type\": \"Sphere\", \"position\": [1,0,0]}, "
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"{\"name\": \"Child2\", \"primitive_type\": \"Cube\", \"parent\": \"Child1\"}]. "
2832
"Use manage_asset action=search filterType=Prefab to list prefabs."
2933
),
3034
annotations=ToolAnnotations(
@@ -59,6 +63,7 @@ async def manage_prefabs(
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parent: Annotated[str, "New parent object name/path within prefab for modify_contents."] | None = None,
6064
components_to_add: Annotated[list[str], "Component types to add in modify_contents."] | None = None,
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components_to_remove: Annotated[list[str], "Component types to remove in modify_contents."] | None = None,
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create_child: Annotated[dict[str, Any] | list[dict[str, Any]], "Create child GameObject(s) in the prefab. Single object or array of objects, each with: name (required), parent (optional, defaults to target), primitive_type (optional: Cube, Sphere, Capsule, Cylinder, Plane, Quad), position, rotation, scale, components_to_add, tag, layer, set_active."] | None = None,
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) -> dict[str, Any]:
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# Back-compat: map 'name' → 'target' for create_from_gameobject (Unity accepts both)
6469
if action == "create_from_gameobject" and target is None and name is not None:
@@ -143,6 +148,36 @@ async def manage_prefabs(
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params["componentsToAdd"] = components_to_add
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if components_to_remove is not None:
145150
params["componentsToRemove"] = components_to_remove
151+
if create_child is not None:
152+
# Normalize vector fields within create_child (handles single object or array)
153+
def normalize_child_params(child: Any, index: int | None = None) -> tuple[dict | None, str | None]:
154+
prefix = f"create_child[{index}]" if index is not None else "create_child"
155+
if not isinstance(child, dict):
156+
return None, f"{prefix} must be a dict with child properties (name, primitive_type, position, etc.), got {type(child).__name__}"
157+
child_params = dict(child)
158+
for vec_field in ("position", "rotation", "scale"):
159+
if vec_field in child_params and child_params[vec_field] is not None:
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vec_val, vec_err = normalize_vector3(child_params[vec_field], f"{prefix}.{vec_field}")
161+
if vec_err:
162+
return None, vec_err
163+
child_params[vec_field] = vec_val
164+
return child_params, None
165+
166+
if isinstance(create_child, list):
167+
# Array of children
168+
normalized_children = []
169+
for i, child in enumerate(create_child):
170+
child_params, err = normalize_child_params(child, i)
171+
if err:
172+
return {"success": False, "message": err}
173+
normalized_children.append(child_params)
174+
params["createChild"] = normalized_children
175+
else:
176+
# Single child object
177+
child_params, err = normalize_child_params(create_child)
178+
if err:
179+
return {"success": False, "message": err}
180+
params["createChild"] = child_params
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147182
# Send command to Unity
148183
response = await send_with_unity_instance(

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