feat: add component_properties to manage_prefabs modify_contents (#793)

MCPForUnity/Editor/Tools/Prefabs/ManagePrefabs.cs

@@ -758,6 +758,52 @@ private static (bool modified, ErrorResponse error) ApplyModificationsToPrefabOb
                 }
             }
 
+            // Set properties on existing components
+            JObject componentProperties = @params["componentProperties"] as JObject ?? @params["component_properties"] as JObject;
+            if (componentProperties != null && componentProperties.Count > 0)
+            {
+                var errors = new List<string>();
+
+                foreach (var entry in componentProperties.Properties())
+                {
+                    string typeName = entry.Name;
+                    if (!ComponentResolver.TryResolve(typeName, out Type componentType, out string resolveError))
+                    {
+                        errors.Add($"{typeName}: type not found — {resolveError}");
+                        continue;
+                    }
+
+                    Component component = targetGo.GetComponent(componentType);
+                    if (component == null)
+                    {
+                        errors.Add($"{typeName}: not found on '{targetGo.name}'");
+                        continue;
+                    }
+
+                    if (entry.Value is not JObject props || !props.HasValues)
+                    {
+                        continue;
+                    }
+
+                    foreach (var prop in props.Properties())
+                    {
+                        if (!ComponentOps.SetProperty(component, prop.Name, prop.Value, out string setError))
+                        {
+                            errors.Add($"{typeName}.{prop.Name}: {setError}");
+                        }
+                        else
+                        {
+                            modified = true;
+                        }
+                    }
+                }
+
+                if (errors.Count > 0)
+                {
+                    return (false, new ErrorResponse($"Failed to set component properties (no changes saved): {string.Join("; ", errors)}"));
+                }
+            }
+
             return (modified, null);
         }
 

Server/src/services/tools/manage_prefabs.py

@@ -29,6 +29,9 @@
         "(single object or array for batch creation in one save). "
         "Example: create_child=[{\"name\": \"Child1\", \"primitive_type\": \"Sphere\", \"position\": [1,0,0]}, "
         "{\"name\": \"Child2\", \"primitive_type\": \"Cube\", \"parent\": \"Child1\"}]. "
+        "Use component_properties with modify_contents to set serialized fields on existing components "
+        "(e.g. component_properties={\"Rigidbody\": {\"mass\": 5.0}, \"MyScript\": {\"health\": 100}}). "
+        "Supports object references via {\"guid\": \"...\"}, {\"path\": \"Assets/...\"}, or {\"instanceID\": 123}. "
         "Use manage_asset action=search filterType=Prefab to list prefabs."
     ),
     annotations=ToolAnnotations(
@@ -64,6 +67,7 @@ async def manage_prefabs(
     components_to_add: Annotated[list[str], "Component types to add in modify_contents."] | None = None,
     components_to_remove: Annotated[list[str], "Component types to remove in modify_contents."] | None = None,
     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,
+    component_properties: Annotated[dict[str, dict[str, Any]], "Set properties on existing components in modify_contents. Keys are component type names, values are dicts of property name to value. Example: {\"Rigidbody\": {\"mass\": 5.0}, \"MyScript\": {\"health\": 100}}. Supports object references via {\"guid\": \"...\"}, {\"path\": \"Assets/...\"}, or {\"instanceID\": 123}."] | None = None,
 ) -> dict[str, Any]:
     # Back-compat: map 'name' → 'target' for create_from_gameobject (Unity accepts both)
     if action == "create_from_gameobject" and target is None and name is not None:
@@ -148,6 +152,8 @@ async def manage_prefabs(
             params["componentsToAdd"] = components_to_add
         if components_to_remove is not None:
             params["componentsToRemove"] = components_to_remove
+        if component_properties is not None:
+            params["componentProperties"] = component_properties
         if create_child is not None:
             # Normalize vector fields within create_child (handles single object or array)
             def normalize_child_params(child: Any, index: int | None = None) -> tuple[dict | None, str | None]:

Server/tests/test_manage_prefabs.py

@@ -0,0 +1,38 @@
+"""Tests for manage_prefabs tool - component_properties parameter."""
+
+import inspect
+
+from services.tools.manage_prefabs import manage_prefabs
+
+
+class TestManagePrefabsComponentProperties:
+    """Tests for the component_properties parameter on manage_prefabs."""
+
+    def test_component_properties_parameter_exists(self):
+        """The manage_prefabs tool should have a component_properties parameter."""
+        sig = inspect.signature(manage_prefabs)
+        assert "component_properties" in sig.parameters
+
+    def test_component_properties_parameter_is_optional(self):
+        """component_properties should default to None."""
+        sig = inspect.signature(manage_prefabs)
+        param = sig.parameters["component_properties"]
+        assert param.default is None
+
+    def test_tool_description_mentions_component_properties(self):
+        """The tool description should mention component_properties."""
+        from services.registry import get_registered_tools
+        tools = get_registered_tools()
+        prefab_tool = next(
+            (t for t in tools if t["name"] == "manage_prefabs"), None
+        )
+        assert prefab_tool is not None
+        # Description is stored at top level or in kwargs depending on how the decorator stores it
+        desc = prefab_tool.get("description") or prefab_tool.get("kwargs", {}).get("description", "")
+        assert "component_properties" in desc
+
+    def test_required_params_include_modify_contents(self):
+        """modify_contents should be a valid action requiring prefab_path."""
+        from services.tools.manage_prefabs import REQUIRED_PARAMS
+        assert "modify_contents" in REQUIRED_PARAMS
+        assert "prefab_path" in REQUIRED_PARAMS["modify_contents"]

TestProjects/UnityMCPTests/Assets/Tests/EditMode/Tools/ManagePrefabsCrudTests.cs

@@ -722,6 +722,204 @@ public void ModifyContents_CreateChild_ReturnsErrorForInvalidInput()
 
         #endregion
 
+        #region Component Properties Tests
+
+        [Test]
+        public void ModifyContents_ComponentProperties_SetsSimpleProperties()
+        {
+            string prefabPath = CreatePrefabWithComponents("CompPropSimple", typeof(Rigidbody));
+
+            try
+            {
+                var result = ToJObject(ManagePrefabs.HandleCommand(new JObject
+                {
+                    ["action"] = "modify_contents",
+                    ["prefabPath"] = prefabPath,
+                    ["componentProperties"] = new JObject
+                    {
+                        ["Rigidbody"] = new JObject
+                        {
+                            ["mass"] = 42f,
+                            ["useGravity"] = false
+                        }
+                    }
+                }));
+
+                Assert.IsTrue(result.Value<bool>("success"), $"Expected success but got: {result}");
+                Assert.IsTrue(result["data"].Value<bool>("modified"));
+
+                // Verify changes persisted
+                GameObject reloaded = AssetDatabase.LoadAssetAtPath<GameObject>(prefabPath);
+                var rb = reloaded.GetComponent<Rigidbody>();
+                Assert.IsNotNull(rb);
+                Assert.AreEqual(42f, rb.mass, 0.01f);
+                Assert.IsFalse(rb.useGravity);
+            }
+            finally
+            {
+                SafeDeleteAsset(prefabPath);
+            }
+        }
+
+        [Test]
+        public void ModifyContents_ComponentProperties_SetsMultipleComponents()
+        {
+            string prefabPath = CreatePrefabWithComponents("CompPropMulti", typeof(Rigidbody), typeof(Light));
+
+            try
+            {
+                var result = ToJObject(ManagePrefabs.HandleCommand(new JObject
+                {
+                    ["action"] = "modify_contents",
+                    ["prefabPath"] = prefabPath,
+                    ["componentProperties"] = new JObject
+                    {
+                        ["Rigidbody"] = new JObject { ["mass"] = 10f },
+                        ["Light"] = new JObject { ["intensity"] = 3.5f }
+                    }
+                }));
+
+                Assert.IsTrue(result.Value<bool>("success"), $"Expected success but got: {result}");
+
+                GameObject reloaded = AssetDatabase.LoadAssetAtPath<GameObject>(prefabPath);
+                Assert.AreEqual(10f, reloaded.GetComponent<Rigidbody>().mass, 0.01f);
+                Assert.AreEqual(3.5f, reloaded.GetComponent<Light>().intensity, 0.01f);
+            }
+            finally
+            {
+                SafeDeleteAsset(prefabPath);
+            }
+        }
+
+        [Test]
+        public void ModifyContents_ComponentProperties_SetsOnChildTarget()
+        {
+            // Create a prefab with a child that has a Rigidbody
+            EnsureFolder(TempDirectory);
+            GameObject root = new GameObject("ChildTargetTest");
+            GameObject child = new GameObject("Child1") { transform = { parent = root.transform } };
+            child.AddComponent<Rigidbody>();
+
+            string prefabPath = Path.Combine(TempDirectory, "ChildTargetTest.prefab").Replace('\\', '/');
+            PrefabUtility.SaveAsPrefabAsset(root, prefabPath, out bool success);
+            UnityEngine.Object.DestroyImmediate(root);
+            AssetDatabase.Refresh();
+            Assert.IsTrue(success);
+
+            try
+            {
+                var result = ToJObject(ManagePrefabs.HandleCommand(new JObject
+                {
+                    ["action"] = "modify_contents",
+                    ["prefabPath"] = prefabPath,
+                    ["target"] = "Child1",
+                    ["componentProperties"] = new JObject
+                    {
+                        ["Rigidbody"] = new JObject { ["mass"] = 99f, ["drag"] = 2.5f }
+                    }
+                }));
+
+                Assert.IsTrue(result.Value<bool>("success"), $"Expected success but got: {result}");
+
+                GameObject reloaded = AssetDatabase.LoadAssetAtPath<GameObject>(prefabPath);
+                var childRb = reloaded.transform.Find("Child1").GetComponent<Rigidbody>();
+                Assert.AreEqual(99f, childRb.mass, 0.01f);
+                Assert.AreEqual(2.5f, childRb.drag, 0.01f);
+            }
+            finally
+            {
+                SafeDeleteAsset(prefabPath);
+            }
+        }
+
+        [Test]
+        public void ModifyContents_ComponentProperties_ReturnsErrorForMissingComponent()
+        {
+            string prefabPath = CreateTestPrefab("CompPropMissing");
+
+            try
+            {
+                var result = ToJObject(ManagePrefabs.HandleCommand(new JObject
+                {
+                    ["action"] = "modify_contents",
+                    ["prefabPath"] = prefabPath,
+                    ["componentProperties"] = new JObject
+                    {
+                        ["Rigidbody"] = new JObject { ["mass"] = 5f }
+                    }
+                }));
+
+                Assert.IsFalse(result.Value<bool>("success"));
+                Assert.IsTrue(result.Value<string>("error").Contains("not found"),
+                    $"Expected 'not found' error but got: {result.Value<string>("error")}");
+            }
+            finally
+            {
+                SafeDeleteAsset(prefabPath);
+            }
+        }
+
+        [Test]
+        public void ModifyContents_ComponentProperties_ReturnsErrorForInvalidType()
+        {
+            string prefabPath = CreateTestPrefab("CompPropInvalidType");
+
+            try
+            {
+                var result = ToJObject(ManagePrefabs.HandleCommand(new JObject
+                {
+                    ["action"] = "modify_contents",
+                    ["prefabPath"] = prefabPath,
+                    ["componentProperties"] = new JObject
+                    {
+                        ["NonexistentComponent"] = new JObject { ["foo"] = "bar" }
+                    }
+                }));
+
+                Assert.IsFalse(result.Value<bool>("success"));
+                Assert.IsTrue(result.Value<string>("error").Contains("not found"),
+                    $"Expected 'not found' error but got: {result.Value<string>("error")}");
+            }
+            finally
+            {
+                SafeDeleteAsset(prefabPath);
+            }
+        }
+
+        [Test]
+        public void ModifyContents_ComponentProperties_CombinesWithOtherModifications()
+        {
+            string prefabPath = CreatePrefabWithComponents("CompPropCombined", typeof(Rigidbody));
+
+            try
+            {
+                var result = ToJObject(ManagePrefabs.HandleCommand(new JObject
+                {
+                    ["action"] = "modify_contents",
+                    ["prefabPath"] = prefabPath,
+                    ["position"] = new JArray(5f, 10f, 15f),
+                    ["name"] = "RenamedWithProps",
+                    ["componentProperties"] = new JObject
+                    {
+                        ["Rigidbody"] = new JObject { ["mass"] = 25f }
+                    }
+                }));
+
+                Assert.IsTrue(result.Value<bool>("success"), $"Expected success but got: {result}");
+
+                GameObject reloaded = AssetDatabase.LoadAssetAtPath<GameObject>(prefabPath);
+                Assert.AreEqual("RenamedWithProps", reloaded.name);
+                Assert.AreEqual(new Vector3(5f, 10f, 15f), reloaded.transform.localPosition);
+                Assert.AreEqual(25f, reloaded.GetComponent<Rigidbody>().mass, 0.01f);
+            }
+            finally
+            {
+                SafeDeleteAsset(prefabPath);
+            }
+        }
+
+        #endregion
+
         #region Error Handling
 
         [Test]
@@ -824,6 +1022,24 @@ private static string CreateNestedTestPrefab(string name)
             return path;
         }
 
+        private static string CreatePrefabWithComponents(string name, params Type[] componentTypes)
+        {
+            EnsureFolder(TempDirectory);
+            GameObject temp = new GameObject(name);
+            foreach (var t in componentTypes)
+            {
+                temp.AddComponent(t);
+            }
+
+            string path = Path.Combine(TempDirectory, name + ".prefab").Replace('\\', '/');
+            PrefabUtility.SaveAsPrefabAsset(temp, path, out bool success);
+            UnityEngine.Object.DestroyImmediate(temp);
+            AssetDatabase.Refresh();
+
+            if (!success) throw new Exception($"Failed to create test prefab at {path}");
+            return path;
+        }
+
         private static string CreateComplexTestPrefab(string name)
         {
             // Creates: Vehicle (root with BoxCollider)