Bug: UnityEvent Wiring Clears m_Calls Instead of Setting Them

[h2v9696]

Description

When attempting to wire custom UnityEvent<T> fields via manage_components with set_property, MCP reports success but clears the m_Calls array instead of populating it with the provided callback data.

This affects both underscore-prefixed fields (_onEditClicked) and likely all UnityEvent fields.

Steps to Reproduce

1. Create a MonoBehaviour with a UnityEvent field:

[SerializeField] private UnityEvent<MyType> _onCustomEvent;

2. Wire the event manually in Unity Inspector (so m_Calls has data)

3. Try to update via MCP:

{
  "tool": "manage_components",
  "params": {
    "action": "set_property",
    "target": 73018,
    "search_method": "by_id",
    "component_type": "NoteSystem.Views.UIRecurringNoteItem",
    "properties": {
      "_onEditClicked": {
        "m_PersistentCalls": {
          "m_Calls": [{
            "m_Target": {"instanceID": 73180},
            "m_TargetAssemblyTypeName": "NoteSystem.Views.UIRecurringNoteList, Assembly-CSharp",
            "m_MethodName": "OnItemEditClicked",
            "m_Mode": 0,
            "m_CallState": 2
          }]
        }
      }
    }
  }
}

4. MCP returns: {"success": true, "message": "Properties set..."}

5. Save scene and check .unity file - the event is now empty:

_onEditClicked:
  m_PersistentCalls:
    m_Calls: []

Expected Behavior

The m_Calls array should be populated with the provided callback:

_onEditClicked:
  m_PersistentCalls:
    m_Calls:
    - m_Target: {fileID: 794262283}
      m_TargetAssemblyTypeName: NoteSystem.Views.UIRecurringNoteList, Assembly-CSharp
      m_MethodName: OnItemEditClicked
      m_Mode: 0
      m_CallState: 2

Actual Behavior

• MCP reports success
• m_Calls array is cleared/emptied
• Previously wired events are lost

Additional Context

• MCP version: Latest from main branch
• Unity version: 6000.1.2f1 (Unity 6)
• The field IS found (no "property not found" error)
• The issue is in serialization of the UnityEvent structure

Suggestion

The UnityEvent serialization likely needs special handling. When setting m_PersistentCalls.m_Calls, the code should:

1. Create proper PersistentCall objects
2. Resolve instanceID to proper Unity object references
3. Use SerializedObject/SerializedProperty API for reliable serialization

Workaround

Edit .unity scene file directly using fileIDs instead of instanceIDs.

[whatevertogo]

Should we refactor all reflection-based logic to consistently use the SerializedProperty API, or should we just apply a targeted patch for this specific issue?

[h2v9696]

@whatevertogo I think a targeted patch would be a good approach. In my coding conventions, and in many other teams, using the SerializedProperty API is considered a must. However, since not all code strictly follows SOLID principles, supporting both approaches would provide better compatibility.