[Experiment] Debugging Reducers in SwiftUI Previews

[tgrapperon]

Hello!

While working on hyper-modularized projects, it can be sometimes inconvenient to spin an app to inspect things a little closer (even dedicated feature apps). I'm aware that you can hook the debugger onto the Previews' process, but this is also quite inconvenient to do.

These helpers allow to print the result of .debug() reducers to live SwiftUI Previews (which are the default mode starting from Xcode 14). You only need to use .debugUI() instead of .debug() on the reducers you want to inspect, and use the .debugUI() view modifier in your previews. This .debugUI modifier optionally allows to specify an alignment (.top or .bottom for example) as well as a height or the font size for the virtual console. It displays it as a static overlay on top of its view.

I made the feature so it can run on iOS 13, with the smallest footprint possible. It is self-contained in a 200 lines single file that you can use in your projects, whatever branch of TCA you're using right now.

It is obvious that SwiftUI could allow even more than simple logs, especially with protocol reducers, but I feel that this already helps a lot.

What do you think about it?

[tgrapperon]

I've added some button to toggle the console's visibility and a printUI(_ message: String, color: Color? = nil)
"command" that you can use to manually print in the console.

Since this is a View, you can use it anywhere, including in bodies. You can also use it in .task or .run effects. Using a single struct that starts with a lowercase letter is a little hackish. It is of course possible to define a free function and a PrintUI view instead. This printUI utility can probably be overloaded to match Swift.print API.