@StateObject is initialized twice for the same view instance?

This looks like a SwiftUI bug, but maybe I'm doing something wrong.

The documentation for @StateObject says: "SwiftUI creates a new instance of the object only once for each instance of the structure that declares the object. "

However, in some cases a @StateObject can be initialized more than once.

For example, this view:

Code Block 
struct DetailView: View {
	@StateObject private var someState = SomeState()
	var body: some View {
		Group {
			Text("Detail view")
		}
		.navigationTitle("Detail View")
		.onAppear {
			logger.debug("On Appear")
		}
	}
}
class SomeState: ObservableObject {
	init() {
		logger.debug("init")
	}
}

when pushed onto a NavigationView using a NavigationLink inside a List, like this:

Code Block 
struct ContentView: View {
	var body: some View {
		NavigationView {
			List {
				NavigationLink(destination: DetailView()
				) {
					Text("Hello World")
				}
			}
		}.navigationViewStyle(DoubleColumnNavigationViewStyle())
	}
}

The output produced is:

[app] init
[app] On Appear
[app] init

As you can see, the SomeState initializer was called twice, when according to the documentation it should only be called once.

If you don't wrap the NavigationLink in a List:

Code Block 
var body: some View {
		NavigationView {
				NavigationLink(destination: DetailView()
				) {
					Text("Hello World")
				}
		}.navigationViewStyle(DoubleColumnNavigationViewStyle())
	}

Then the output is

[app] init
[app] On Appear

Which is as expected.


I have also seen a similar case where onAppear also gets called twice for what should be only one instance of a view