TestURLSession: Fix test_cancelTask()

- Add a delay into the test server response so that the task will always
  be cancelled before the server returns the complete response.

Author: spevans

TestFoundation/HTTPServer.swift

@@ -313,6 +313,16 @@ struct _HTTPRequest {
         return allHeaders
     }
 
+    public func getHeader(for key: String) -> String? {
+        let lookup = key.lowercased()
+        for header in headers {
+            let parts = header.components(separatedBy: ":")
+            if parts[0].lowercased() == lookup {
+                return parts[1].trimmingCharacters(in: CharacterSet(charactersIn: " "))
+            }
+        }
+        return nil
+    }
 }
 
 struct _HTTPResponse {
@@ -365,6 +375,13 @@ public class TestURLSessionServer {
 
     public func readAndRespond() throws {
         let req = try httpServer.request()
+
+        if let value = req.getHeader(for: "x-pause") {
+            if let wait = Double(value), wait > 0 {
+                Thread.sleep(forTimeInterval: wait)
+            }
+        }
+
         if req.uri.hasPrefix("/LandOfTheLostCities/") {
             /* these are all misbehaving servers */
             try httpServer.respondWithBrokenResponses(uri: req.uri)

TestFoundation/TestURLSession.swift

@@ -22,14 +22,14 @@ class TestURLSession : LoopbackServerTest {
             ("test_finishTaskAndInvalidate", test_finishTasksAndInvalidate),
             ("test_taskError", test_taskError),
             ("test_taskCopy", test_taskCopy),
-            //("test_cancelTask", test_cancelTask), // Breaks on Ubuntu18.04, doesnt always cancel
+            ("test_cancelTask", test_cancelTask),
             ("test_taskTimeout", test_taskTimeout),
             ("test_verifyRequestHeaders", test_verifyRequestHeaders),
             ("test_verifyHttpAdditionalHeaders", test_verifyHttpAdditionalHeaders),
             ("test_timeoutInterval", test_timeoutInterval),
             ("test_httpRedirectionWithCompleteRelativePath", test_httpRedirectionWithCompleteRelativePath),
-            ("test_httpRedirectionWithInCompleteRelativePath", test_httpRedirectionWithInCompleteRelativePath), /* temporarily disabled. Needs HTTPServer rework */
-            ("test_httpRedirectionTimeout", test_httpRedirectionTimeout), /* temporarily disabled (https://bugs.swift.org/browse/SR-5751) */
+            ("test_httpRedirectionWithInCompleteRelativePath", test_httpRedirectionWithInCompleteRelativePath),
+            ("test_httpRedirectionTimeout", test_httpRedirectionTimeout),
             ("test_http0_9SimpleResponses", test_http0_9SimpleResponses),
             ("test_outOfRangeButCorrectlyFormattedHTTPCode", test_outOfRangeButCorrectlyFormattedHTTPCode),
             ("test_missingContentLengthButStillABody", test_missingContentLengthButStillABody),
@@ -231,10 +231,11 @@ class TestURLSession : LoopbackServerTest {
         XCTFail("Intermittent failures on Android")
 #else
         let urlString = "http://127.0.0.1:\(TestURLSession.serverPort)/Peru"
-        let url = URL(string: urlString)!
+        var urlRequest = URLRequest(url: URL(string: urlString)!)
+        urlRequest.setValue("2.0", forHTTPHeaderField: "X-Pause")
         let d = DataTask(with: expectation(description: "GET \(urlString): task cancelation"))
         d.cancelExpectation = expectation(description: "GET \(urlString): task canceled")
-        d.run(with: url)
+        d.run(with: urlRequest)
         d.cancel()
         waitForExpectations(timeout: 12)
 #endif