Adding a reason field to expectAsync and expectAsyncUntil

pkg/unittest/lib/src/spread_args_helper.dart

 part of unittest;
 
 const _PLACE_HOLDER = const _ArgPlaceHolder();
 
 /// Used to track unused positional args.
 class _ArgPlaceHolder {
   const _ArgPlaceHolder();
 }
 
 /// Simulates spread arguments using named arguments.
 class _SpreadArgsHelper {
   final Function callback;
   final int minExpectedCalls;
   final int maxExpectedCalls;
   final Function isDone;
   final String id;
+  final String reason;
   int actualCalls = 0;
   final TestCase testCase;
   bool complete;
 
   _SpreadArgsHelper(Function callback, int minExpected, int maxExpected,
-      String id, {bool isDone()})
+      String id, String reason, {bool isDone()})
       : this.callback = callback,
         minExpectedCalls = minExpected,
         maxExpectedCalls = (maxExpected == 0 && minExpected > 0)
             ? minExpected
             : maxExpected,
         this.isDone = isDone,
+        this.reason = reason == null ? '' : '\n$reason',
         this.testCase = currentTestCase,
         this.id = _makeCallbackId(id, callback) {
     ensureInitialized();
     if (testCase == null) {
       throw new StateError("No valid test. Did you forget to run your test "
           "inside a call to test()?");
     }
 
     if (isDone != null || minExpected > 0) {
       testCase._callbackFunctionsOutstanding++;
@@ skipping 27 matching lines @@
   bool shouldCallBack() {
     ++actualCalls;
     if (testCase.isComplete) {
       // Don't run if the test is done. We don't throw here as this is not
       // the current test, but we do mark the old test as having an error
       // if it previously passed.
       if (testCase.result == PASS) {
         testCase._error(
             'Callback ${id}called ($actualCalls) after test case '
             '${testCase.description} has already been marked as '
-            '${testCase.result}.');
+            '${testCase.result}.$reason');
       }
       return false;
     } else if (maxExpectedCalls >= 0 && actualCalls > maxExpectedCalls) {
       throw new TestFailure('Callback ${id}called more times than expected '
-                            '($maxExpectedCalls).');
+                            '($maxExpectedCalls).$reason');
     }
     return true;
   }
 
   void after() {
     if (!complete) {
       if (minExpectedCalls > 0 && actualCalls < minExpectedCalls) return;
       if (isDone != null && !isDone()) return;
 
       // Mark this callback as complete and remove it from the testcase
@@ skipping 63 matching lines @@
   }
 }
 
 typedef _Func0();
 typedef _Func1(a);
 typedef _Func2(a, b);
 typedef _Func3(a, b, c);
 typedef _Func4(a, b, c, d);
 typedef _Func5(a, b, c, d, e);
 typedef _Func6(a, b, c, d, e, f);