add @PlaydateMain macro to remove eventHandler boilerplate

[simonomi]

the macro generates the game variable and eventHandler function, using the declaration it's attached to as the PlaydateGame. the name @PlaydateMain calls back to@main as it fills the same role.

providing a macro does add a dependency on Swift Syntax, but as of Swift 6.2, SwiftPM distributes Swift Syntax pre-built, so it shouldn't impact compile times too much.

finally, i have a question about PlaydateGame. in the examples, the Game type is always defined as a class, but i'm not sure i see any reason it needs to be? given that the protocol doesn't inherit from AnyObject, the macro supports being used on structs, classes, and even enums. since Swift generally recommends using structs over classes unless necessary, can we switch the examples to use a struct instead?

P.S. see also finnvoor/PlaydateKitTemplate#5

[finnvoor]

apologies for the delay, this looks great. I think the main reason I used classes instead of structs was just because it seemed likely to store game state in the Game class, and a struct would require marking a bunch of methods as mutating. I think it's nice to give people the option to use a struct though. We could put the macro in a separate target if anyone complains about compile time, but yeah I think it's probably not going to make much of a difference. Mind updating the examples to use this macro?

thanks!

[simonomi]

alright! the examples have been updated and i went back and added some documentation to the macro. while i personally would prefer a struct with mutating methods over a class, i think you're right that a final class is the correct default!