[Nullability] NSView.Window & SuperView should be allowed to be null

[snechaev]

xamarin-macios/src/appkit.cs

Lines 16088 to 16097 in 9ea3cff

	partial interface NSView : NSDraggingDestination, NSAnimatablePropertyContainer, NSUserInterfaceItemIdentification, NSAppearanceCustomization, NSAccessibilityElementProtocol, NSAccessibility, NSObjectAccessibilityExtensions {
	[DesignatedInitializer]
	[Export ("initWithFrame:")]
	NativeHandle Constructor (CGRect frameRect);
	[Export ("window")]
	NSWindow Window { get; }
	[Export ("superview")]
	NSView Superview { get; }

The current implementation of the NSView.Window marked as non-nullable. But the Apple docs states that:

The value of this property is nil if the view is not currently installed in a window.

The same thing with a NSView.SuperView - the docs:

The value of this property is nil when the view is not installed in a view hierarchy.

[tipa]

This change would finally resolve the false-positive warnings I get in Rider (at least partly): https://youtrack.jetbrains.com/issue/RSRP-494672

I believe the launchOptions parameter for application:didFinishLaunchingWithOptions: should also be annotated as nullable. Plus there's a whole lot more here or here. If it's just a missing annotation that could resolve it, like in the linked PR, it shouldn't be too difficult to resolve all these. Would have certainly prevented some crashes in my case :)

[snechaev]

I believe the launchOptions parameter for application:didFinishLaunchingWithOptions: should also be annotated as nullable.

I don't see this declaration anywhere except in the templates

xamarin-macios/dotnet/Templates/Microsoft.iOS.Templates/ios-tabbed/AppDelegate.cs

Lines 10 to 11 in 9ea3cff

	[Export ("application:didFinishLaunchingWithOptions:")]
	public bool FinishedLaunching (UIApplication application, NSDictionary launchOptions)

So it looks like this can be manually annotated when creating the project (the template should be fixed to avoid manual fixes in the future). @tipa, am I missing some use case (I have no experience with iOS)?

[snechaev]

by the way, the #21599 will only fix this for macos, not ios. I can add commits in the existing PR or create the new one.

https://github.com/xamarin/xamarin-macios/blob/9ea3cff36c86b1c3c46fb0872543165046b507a8/src/uikit.cs#L16921-L16929

[rolfbjarne]

by the way, the #21599 will only fix this for macos, not ios. I can add commits in the existing PR or create the new one.

9ea3cff/src/uikit.cs#L16921-L16929

I've created a PR for iOS as well.