Menu not updating (SwiftUI bug?) - swift

Question

I'm using macOS Montery Beta 4 along with Xcode 13 Beta 4, and I think I've discovered a bug in SwiftUI.
When using a CommandGroup along with a button that is enabled/disabled based on a condition, the CommandGroup doesn't update. CommandMenu does however.
Reproduction:
Create a new SwiftUI macOS project
Paste the following code in the App file:
class Test: ObservableObject {
#Published var num = 0
}
#main
struct TestApp: App {
#StateObject private var test = Test()
var body: some Scene {
WindowGroup {
ContentView()
.environmentObject(test)
}
.commands {
CommandGroup(after: .newItem) {
Button(action: {}) {
Text("Test menu item")
}
.disabled(test.num == 0)
}
}
}
}
Paste the following code in the ContentView file:
struct ContentView: View {
#EnvironmentObject var test: Test
var body: some View {
Button(action: {
test.num += 1
}) {
Text(String(test.num) + " ---------")
}
}
}
Run the app, and click on the File menu. You should see that "Test menu item" is disabled as expected.
Click on the button. This simply increments a number by 1. However, "Test menu item" is still disabled, even though test.num != 0.
The thing is, replacing the CommandGroup with CommandMenu("Test menu") fixes it.
All the app does is have a menu item that is disabled if a number is zero. Pressing the button makes that number not zero, but the menu item stays disabled.
Is anybody able to reproduce this, and is this a bug on my part?

Answer 1

a minor variation of #George_E answer, is this:
CommandGroup(after: .newItem) {
TestView(test: test)
}
struct TestView: View {
#ObservedObject var test: Test
var body: some View {
Button(action: {}) {
Text("Test menu item")
}
.disabled(test.num == 0)
}
}

Answer 2

I wouldn't expect that to be intended behaviour. However, I have found a workaround to fix this.
It's odd that onChange(of:perform:) isn't run when test.num changes, but we can still detect the publisher. So I split this into a separate view and when the view receives a new value, the button is updated.
Code:
CommandGroup(after: .newItem) {
TestView(pub: test.$num)
}
struct TestView: View {
let pub: Published<Int>.Publisher
#State private var disabled = true
var body: some View {
Button(action: {}) {
Text("Test menu item")
}
.disabled(disabled)
.onReceive(pub) { new in
disabled = new == 0
}
}
}