Unity-Technologies/UnityCsReference · error · NotImplementedException

Don't know how to display value.

Error message

Don't know how to display value.

What it means

Thrown when DefaultPluginImporterExtension.OnGUI encounters a property whose Type is not one of the handled primitives (bool, enum, string). The inspector only knows how to render a closed set of types via EditorGUILayout; anything else raises NotImplementedException.

Source

Thrown at Editor/Mono/Modules/DefaultPluginImporterExtension.cs:87

            internal virtual void Apply(PluginImporterInspector inspector)
            {
                string valueString = type == typeof(bool) ? value.ToString().ToLower() : value.ToString();
                inspector.importer.SetPlatformData(platformName, key, valueString);
            }

            internal virtual void OnGUI(PluginImporterInspector inspector)
            {
                if (type == typeof(bool)) value = EditorGUILayout.Toggle(name, (bool)value);
                else if (type.IsEnum)
                {
                    if (type.IsDefined(typeof(FlagsAttribute), false))
                        value = EditorGUILayout.EnumFlagsField(name, (Enum)value);
                    else
                        value = EditorGUILayout.EnumPopup(name, (Enum)value);
                }
                else if (type == typeof(string)) value = EditorGUILayout.TextField(name, (string)value);
                else throw new NotImplementedException("Don't know how to display value.");
            }
        }

        internal bool propertiesRefreshed = false;

        public DefaultPluginImporterExtension(Property[] properties)
        {
            this.properties = properties;
        }

        protected virtual Property[] GetPropertiesForInspector(PluginImporterInspector inspector)
        {
            return properties;
        }

        public virtual void ResetValues(PluginImporterInspector inspector)
        {
            hasModified = false;

View on GitHub (pinned to 225b0fbdb5)

Solutions

1. Subclass DefaultPluginImporterExtension and override OnGUI to add handling for the custom type before calling base.OnGUI.
2. Change the Property type to a supported primitive (bool, enum, or string) in the plugin's metadata.
3. If the property is not user-editable, remove it from GetPropertiesForInspector so it is never rendered.

Example fix

// before
else if (type == typeof(string)) value = EditorGUILayout.TextField(name, (string)value);
else throw new NotImplementedException("Don't know how to display value.");
// after: extend the dispatch
else if (type == typeof(float)) value = EditorGUILayout.FloatField(name, (float)value);
else if (type == typeof(int)) value = EditorGUILayout.IntField(name, (int)value);
else throw new NotImplementedException($"Don't know how to display value of type {type}.");

static readonly HashSet<Type> k_Supported = new(){ typeof(bool), typeof(string) };
bool CanDisplay(Type t) => k_Supported.Contains(t) || t.IsEnum;

static bool IsInspectableProperty(Type type) =>
    type == typeof(bool) || type.IsEnum || type == typeof(string);

try { inspector.OnGUI(); }
catch (NotImplementedException) { /* hide the unsupported property row */ }

When it happens

Trigger: A native plugin declares a Property whose Type is, e.g., int, float, Vector3, double, or any custom/struct type, and the plugin importer inspector tries to render it. OnGUI dispatches through if/else chains and hits the final else.

Common situations: Third-party or custom platform plugin returns properties with numeric or struct types that the default inspector GUI does not support. Plugin SDK version change introduces a new property type.

Related errors

• Unexpected mixed value for '{assetPath}', platform: {platfor
• path
• paths
• Cannot call ReportAssetChanged outside of the OnAssetsModifi
• Cannot add dependency on invalid path.

AI-assisted analysis of Unity-Technologies/UnityCsReference@225b0fbdb5 (2026-08-13). Data as JSON: /api/errors/a198b34935f7c767. Report an issue: GitHub.