When redirecting with a relative Location, add the port number to the new url

Foundation/URLSession/http/HTTPURLProtocol.swift

@@ -414,7 +414,12 @@ internal extension _HTTPURLProtocol {
         var components = URLComponents()
         components.scheme = scheme
         components.host = host
-        components.port = port
+        // Use the original port if the new URL does not contain a host
+        // ie Location: /foo => <original host>:<original port>/Foo
+        // but Location: newhost/foo  will ignore the original port
+        if targetURL.host == nil {
+          components.port = port
+        }
         //The path must either begin with "/" or be an empty string.
         if targetURL.relativeString.first != "/" {
             components.path = "/" + targetURL.relativeString

TestFoundation/HTTPServer.swift

@@ -522,6 +522,13 @@ public class TestURLSessionServer {
             let httpResponse = _HTTPResponse(response: .REDIRECT, headers: "Location: \(value)", body: text)
             return httpResponse
         }
+        if uri == "/redirect-with-default-port" {
+            let text = request.getCommaSeparatedHeaders()
+            let host = request.headers[1].components(separatedBy: " ")[1]
+            let ip = host.components(separatedBy: ":")[0]
+            let httpResponse = _HTTPResponse(response: .REDIRECT, headers: "Location: http://\(ip)/redirected-with-default-port", body: text)
+            return httpResponse
+        }
         return _HTTPResponse(response: .OK, body: capitals[String(uri.dropFirst())]!)
     }
 

TestFoundation/TestURLSession.swift

@@ -29,6 +29,7 @@ class TestURLSession : LoopbackServerTest {
             ("test_timeoutInterval", test_timeoutInterval),
             ("test_httpRedirectionWithCompleteRelativePath", test_httpRedirectionWithCompleteRelativePath),
             ("test_httpRedirectionWithInCompleteRelativePath", test_httpRedirectionWithInCompleteRelativePath),
+            ("test_httpRedirectionWithDefaultPort", test_httpRedirectionWithDefaultPort),
             ("test_httpRedirectionTimeout", test_httpRedirectionTimeout),
             ("test_http0_9SimpleResponses", test_http0_9SimpleResponses),
             ("test_outOfRangeButCorrectlyFormattedHTTPCode", test_outOfRangeButCorrectlyFormattedHTTPCode),
@@ -345,6 +346,14 @@ class TestURLSession : LoopbackServerTest {
         waitForExpectations(timeout: 12)
     }
 
+    func test_httpRedirectionWithDefaultPort() {
+        let urlString = "http://127.0.0.1:\(TestURLSession.serverPort)/redirect-with-default-port"
+        let url = URL(string: urlString)!
+        let d = HTTPRedirectionDataTask(with: expectation(description: "GET \(urlString): with HTTP redirection"))
+        d.run(with: url)
+        waitForExpectations(timeout: 12)
+    }
+
      // temporarily disabled (https://bugs.swift.org/browse/SR-5751)
     func test_httpRedirectionTimeout() {
         let urlString = "http://127.0.0.1:\(TestURLSession.serverPort)/UnitedStates"
@@ -915,6 +924,11 @@ extension HTTPRedirectionDataTask : URLSessionTaskDelegate {
     public func urlSession(_ session: URLSession, task: URLSessionTask, willPerformHTTPRedirection response: HTTPURLResponse, newRequest request: URLRequest, completionHandler: @escaping (URLRequest?) -> Void) {
         XCTAssertNotNil(response)
         XCTAssertEqual(302, response.statusCode, "HTTP response code is not 302")
+        if let url = response.url, url.path.hasSuffix("/redirect-with-default-port") {
+            XCTAssertEqual(request.url?.absoluteString, "http://127.0.0.1/redirected-with-default-port")
+            // Dont follow the redirect as the test server is not running on port 80
+            return
+        }
         completionHandler(request)
     }
 }