Darwin Option 4

Author: johnno1962

Foundation/URLSession/URLSessionTask.swift

@@ -88,7 +88,6 @@ open class URLSessionTask : NSObject, NSCopying {
                 self._protocol = urlProtocol.init(task: self, cachedResponse: nil, client: nil)
             }
         }
-        guard self._protocol != nil else { fatalError("Unable to find protocol handler for \(request)") }
     }
     deinit {
         //TODO: Do we remove the EasyHandle from the session here? This might run on the wrong thread / queue.
@@ -251,7 +250,20 @@ open class URLSessionTask : NSObject, NSCopying {
             self.updateTaskState()
             if self.suspendCount == 0 {
                 self.workQueue.async {
-                    self._protocol?.startLoading()
+                    if let _protocol = self._protocol {
+                        _protocol.startLoading()
+                    }
+                    else {
+                        var userInfo: [String: Any] = [NSLocalizedDescriptionKey: "unsupported URL"]
+                        if let url = self.originalRequest?.url {
+                            userInfo[NSURLErrorFailingURLErrorKey] = url
+                            userInfo[NSURLErrorFailingURLStringErrorKey] = url.absoluteString
+                        }
+                        let error = NSError(domain: NSURLErrorDomain,
+                                            code: URLError.unsupportedURL.rawValue,
+                                            userInfo: userInfo)
+                        _ProtocolClient().urlProtocol(task: self, didFailWithError: error)
+                    }
                 }
             }
         }
@@ -576,6 +588,10 @@ extension _ProtocolClient : URLProtocolClient {
 
     func urlProtocol(_ protocol: URLProtocol, didFailWithError error: Error) {
         guard let task = `protocol`.task else { fatalError() }
+        urlProtocol(task: task, didFailWithError: error)
+    }
+
+    func urlProtocol(task: URLSessionTask, didFailWithError error: Error) {
         guard let session = task.session as? URLSession else { fatalError() }
         switch session.behaviour(for: task) {
         case .taskDelegate(let delegate):