Swift URL returns nil when the url contains an internationalized domain name (IDN) - swift

Question

I was wondering why this piece of code always exit with 1:
import Foundation
// an idn domain:
let uLabel = "համընդհանուր-ընկալում-թեստ.հայ"
let urlStr = "https://" + uLabel
guard let url = URL(string: urlStr) else { exit(1) }
exit(0)
Since Apple's browser Safari does support well IDN domains, I was surprised their URL library does not... I tried to urlencode the string beforehand, but it is not helping.
======EDIT======
After fixing the piece above upon Matt's suggestion, I faced another problem during fetching the website data:
import Foundation
let uLabel = "համընդհանուր-ընկալում-թեստ.հայ"
let scheme = "https"
var comps = URLComponents()
comps.scheme = scheme
comps.host = uLabel
guard let url = comps.url else { exit(1) }
let task = URLSession.shared.dataTask(with: url) { data, response, error in
guard let rawContent = data else { exit(1) }
guard let content = String(data: rawContent, encoding: String.Encoding.utf8) else { exit(1) }
if content.contains("UASG Testbed Landing Page") {
// successfully fetch content of the page
exit(0)
} else {
// error during fetching
exit(1)
}
}
task.resume()
RunLoop.main.run()
The program still exits with 1. It seems the domain is not converted to an A-LABEL as it is on Safari, as the error suggests (the certificate is valid, the error is misleading):
NSLocalizedDescription=The certificate for this server is invalid. You might be connecting to a server that is pretending to be “համընդհանուր-ընկալում-թեստ.հայ” which could put your confidential information at risk., NSErrorFailingURLKey=https://%d5%b0%d5%a1%d5%b4%d5%a8%d5%b6%d5%a4%d5%b0%d5%a1%d5%b6%d5%b8%d6%82%d6%80-%d5%a8%d5%b6%d5%af%d5%a1%d5%ac%d5%b8%d6%82%d5%b4-%d5%a9%d5%a5%d5%bd%d5%bf.%d5%b0%d5%a1%d5%b5/,

Answer 1

I don't know why you're having trouble, but rule number one is never never never call URL(string). Use URLComponents. That's what it's for.
let uLabel = "համընդհանուր-ընկալում-թեստ.հայ"
let scheme = "https"
var comps = URLComponents()
comps.scheme = scheme
comps.host = uLabel
let url = comps.url // works for me

Answer 2

Until, someone can find a way to tell the URL framework to correctly represent the URL "https://համընդհանուր-ընկալում-թեստ.հայ", it is possible to translate the domain part to an A-LABEL before passing it to the URL constructor and elude its wrong internal representation:
import Foundation
import IDNA
// an idn domain:
let uLabel = "համընդհանուր-ընկալում-թեստ.հայ"
guard let aLabel = uLabel.idnaEncoded else { exit(1) }
let supportedUrl = "https://" + aLabel
guard let url = URL(string: supportedUrl) else { exit(1) }
let task = URLSession.shared.dataTask(with: url) { data, response, error in
guard let rawContent = data else { exit(1) }
guard let content = String(data: rawContent, encoding: String.Encoding.utf8) else { exit(1) }
if content.contains("UASG Testbed Landing Page") {
// successfully fetch content of the page
exit(0)
} else {
// error during fetching
exit(1)
}
}
task.resume()
RunLoop.main.run()
This piece of code does exit 0. The IDNA library is there (ensure you take the master branch, because released versions are still on IDNA2003):
https://github.com/Wevah/IDNA-Cocoa