Support project Catalyst

[iamDecode]

Using RxSwift in an iOS app compiled for Mac currently yields nasty errors because UIWebView is deprecated and not supported in UIKit for Mac:

Undefined symbols for architecture x86_64:
  "_OBJC_CLASS_$_UIWebView", referenced from:
      objc-class-ref in RxWebViewDelegateProxy.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)

The official documentation states #if !targetEnvironment(UIKitForMac) is the best way of dealing with these issues (source).

This PR adds some extra conditions to support compiling with project Catalyst.

[freak4pc]

This is excellent! If this works in Xcode 10 and builds, I'm all for it. Let's wait for CI.

[freak4pc]

So, RxCocoa fails build because of a warning that the targetEnvironment is unknown.

I'd really want to find away around this, if you have any ideas.

I thought wrapping it in a #if compiler(>=5.1) would work but it doesn't seem like it.

[iamDecode]

I've stared at this for a while, but I cant seem to find my way around this. It is parsed, even if we do something like #if false && targetEnvironment(UIKitForMac) or nesting as @freak4pc suggested. I was not able to silence that specific warning; that does not seem possible for Swift other than silencing all warnings for the target (relevant source).

[freak4pc]

@iamDecode I opened a bug in Swift Compiler:
https://bugs.swift.org/browse/SR-10973

There seems to be a fix here, we might need to pull this in and bite the bullet, but let me think of options until tomorrow:
swiftlang/swift#25593

[kzaher]

I think it should be ok to just add --allow-warnings to podfile verification.

It's probably better to allow users to use it with warnings than have it fail.

[freak4pc]

Yup. That would be the only option here - it’s a parser but which was fixed but only for Xcode 11. Can you add it to Travis ? @iamDecode

[iamDecode]

@freak4pc sure thing, I updated it! I added a bit of logic to only add --allow-warnings argument for the RxCocoa target, would be a bit much to add it globally.

[freak4pc]

Looks great! Thanks for your patience.