For now I tried to include a SwiftUI file in Today Widget and open it to edit in Xcode Canvas, and I get:
"xxxwidget.appex" failed to get build settings: unsupportedProductType("com.apple.product-type.app-extension", <Xcode3TargetProduct:0x7f92583d4170:xxxwidget.appex
Is that means SwiftUI is currently not supported in Today Widget? If so, when will it be supported?