PropertyAttribute/Drawer used to auto-filter ObjectPicker window (showing assets / scene references) by name - Unity, IMGUI

ExampleUsage.cs

// Example usage in some other script

[FilterObjectPicker("Projectile")]
public GameObject projectilePrefab;

// When clicking object field in inspector, would only see gameobjects with "Projectile" in name.
// Can remove filter text at top of object picker to see all gameobjects again.
// To allow scene references, add second param as true. e.g. :

[FilterObjectPicker("Test", true)]
public GameObject someSceneObject;

// (These scripts were created/tested in Unity 2022.2)

FilterObjectPickerAttribute.cs

using UnityEngine;

public class FilterObjectPickerAttribute : PropertyAttribute {

    public string filter;
    public bool allowSceneObjects;

    public FilterObjectPickerAttribute(string filter, bool allowSceneObjects = false){
        this.filter = filter;
        this.allowSceneObjects = allowSceneObjects;
    }
}

FilterObjectPickerPropertyDrawer.cs

// (Put under Editor folder)

using UnityEngine;
using UnityEditor;

[CustomPropertyDrawer(typeof(FilterObjectPickerAttribute))]
public class FilterObjectPickerPropertyDrawer : PropertyDrawer {

    public override void OnGUI(Rect position, SerializedProperty property, GUIContent label) {
        EditorGUI.BeginProperty(position, label, property);

        int controlID = GUIUtility.GetControlID(FocusType.Passive);
        Event e = Event.current;
        if (e.type == EventType.MouseUp && position.Contains(e.mousePosition)) {
            e.Use();
            System.Type type = fieldInfo.FieldType;
            if (type.IsArray){ // e.g. GameObject[]
                type = type.GetElementType();
            }else if (type.IsGenericType && type.GenericTypeArguments.Length > 0){ // e.g. List<GameObject>
                type = type.GenericTypeArguments[0];
            }
            // some common types, feel free to add more if needed.
            // not sure if there's a better way to handle this
            if (type == typeof(GameObject)) {
                ShowObjectPicker<GameObject>(property.objectReferenceValue, controlID);
            } else if (type == typeof(Mesh)) {
                ShowObjectPicker<Mesh>(property.objectReferenceValue, controlID);
            } else if (type == typeof(Material)) {
                ShowObjectPicker<Material>(property.objectReferenceValue, controlID);
            } else if (type == typeof(Texture2D)) {
                ShowObjectPicker<Texture2D>(property.objectReferenceValue, controlID);
            } else if (type == typeof(Sprite)) {
                ShowObjectPicker<Sprite>(property.objectReferenceValue, controlID);
            } else if (type.BaseType == typeof(ScriptableObject)) {
                // will show all scriptable object types, but better than showing other assets
                ShowObjectPicker<ScriptableObject>(property.objectReferenceValue, controlID);
            } else {
                // a different type, have to just show all assets... :\
                ShowObjectPicker<Object>(property.objectReferenceValue, controlID);
            }
        } else if (e.type == EventType.ExecuteCommand && e.commandName == "ObjectSelectorUpdated" && controlID == EditorGUIUtility.GetObjectPickerControlID()) {
            e.Use();
            property.objectReferenceValue = EditorGUIUtility.GetObjectPickerObject();
        }
        EditorGUI.PropertyField(position, property, label);
        EditorGUI.EndProperty();
    }

    public void ShowObjectPicker<T>(Object obj, int controlID) where T : Object {
        var att = (FilterObjectPickerAttribute)attribute;
        EditorGUIUtility.ShowObjectPicker<T>(obj, att.allowSceneObjects, att.filter, controlID);
    }
}