feat: Implemented customizable implementation of URLSession.dataTask in a given HTTPRequest

Author: Fabrizio Scarano

Sources/RealHTTP/Client/HTTPRequest/HTTPRequest.swift

@@ -170,6 +170,13 @@ public class HTTPRequest: CustomStringConvertible {
     /// running in a specified `HTTPClient` instance.
     public var urlRequestModifier: RequestModifier?
 
+    /// Defines a default or custom implementation of `URLSession.dataTask(with:)` to execute
+    /// when using a `.default` transfer mode.
+    ///
+    /// Unless set with a custom implementation (using `.modified(DataTask)` enum case), the request
+    /// executes on the default implementation.
+    public var dataTaskModifier: DataTaskModifier = .default
+    
     // MARK: - Private Properties
 
     /// Current network attempt. Use `maxRetries` to set the number of attempts
@@ -429,7 +436,7 @@ extension HTTPRequest {
         } else {
             switch transferMode {
             case .default:
-                task = client.session.dataTask(with: urlRequest)
+                task = dataTaskModifier.dataTask(with: urlRequest, on: client.session)
             case .largeData:
                 if let partialData = partialData {
                     task = client.session.downloadTask(withResumeData: partialData)
@@ -518,6 +525,25 @@ extension HTTPRequest {
         case largeData
     }
 
+    /// Defines a default or custom implementation of `URLSession.dataTask(with:)`.
+    ///
+    /// - `default`: Uses the default `URLSession.dataTask(with:)` implementation.
+    /// - `modifier`: Uses the custom implementation given in its associated value.
+    public enum DataTaskModifier {
+        public typealias DataTask = (URLRequest, URLSession) -> URLSessionDataTask
+        
+        case `default`
+        case modifier(DataTask)
+        
+        public func dataTask(with urlRequest: URLRequest, on session: URLSession) -> URLSessionDataTask {
+            switch self {
+            case .default:
+                session.dataTask(with: urlRequest)
+            case .modifier(let dataTask):
+                dataTask(urlRequest, session)
+            }
+        }
+    }
 }
 
 extension URLComponents {