I'm on High Sierra with Xcode Version 9.0.1 (9A1004). When running
tns doctor I get the following warning:
WARNING: Xcode is not installed or is not configured properly. You will not be able to build your projects for iOS or run them in the iOS Simulator. To be able to build for iOS and run apps in the native emulator, verify that you have installed Xcode.
If I run the installation script, furthermore I get:
xcode-select: error: tool 'xcodebuild' requires Xcode, but active developer directory '/Library/Developer/CommandLineTools' is a command line tools instance Xcode is not installed or not configured properly. Download, install, set it up and run this script again.
As you might have guessed, I have Xcode installed from the app store and I've also installed cocoapods and xcodeproj. This is the only warning that I get.