SwiftUI modifying state warning - pointing to @main

May be you could show some code ? Or at least the detailed log report.

Here's my custom StoredRoutes type:

import Foundation

final class StoredRoutes: NSObject, NSSecureCoding {
    static var supportsSecureCoding: Bool = true

    func encode(with coder: NSCoder) {
        var routeids: [NSString] = []
        for route in routes {
            routeids.append(NSString(string: route.rawValue))
        }
        coder.encode(NSArray(array: routeids), forKey: "routes")
    }

    init?(coder: NSCoder) {
        if let nsArray = coder.decodeObject(of: NSArray.self, forKey: "routes") {
            self.routes = []
            for id in nsArray {
                self.routes.append(Route(rawValue: id as! String)!)
            }
        } else {
            return nil
        }
    }

    var routes: [Route]

    required init(routes: [Route]) {
        self.routes = routes
    }
}

and my value transformer:

import Foundation

final class StoredRoutesValueTransformer: NSSecureUnarchiveFromDataTransformer {
    
    static var name = NSValueTransformerName(rawValue: "StoredRoutesValueTransformer")
    
    override class func allowsReverseTransformation() -> Bool {
        return true
    }
    
    override class func transformedValueClass() -> AnyClass {
        return StoredRoutes.self
    }
    
    override class var allowedTopLevelClasses: [AnyClass] {
        return [StoredRoutes.self, NSArray.self, NSString.self]
    }
    
    override func transformedValue(_ value: Any?) -> Any? {
        guard let data = value as? Data else {
            fatalError("Wrong data type: value must be of type Data. The type the value recieved was \(type(of: value)).")
        }
        return super.transformedValue(data)
    }
    
    override func reverseTransformedValue(_ value: Any?) -> Any? {
        guard let storedRoutes = value as? StoredRoutes else {
            fatalError("Wrong data type: value must be of type StoredRoutes. The type of the value recieved was \(type(of: value))")
        }
        return super.reverseTransformedValue(storedRoutes)
    }

    public static func register() {
        let transformer = StoredRoutesValueTransformer()
        ValueTransformer.setValueTransformer(transformer, forName: name)
    }
}

I am also experiencing this. I didn't make any changes that effect any kind of state whatsoever. I merely attempted to edit the Entitlements File, and then undid the changes. This error appeared and now it won't go away. Even reverting to previous builds doesn't make it stop