Fixed bug in Task implementation

Add ability to write a task continuation that changes the task result

Author: nikhilk

src/Core/CoreLib/Threading/Task.cs

@@ -50,6 +50,10 @@ public static Task<Task> Any(int timeout, params Task[] tasks) {
             return null;
         }
 
+        public Task<TResult> ChangeWith<TResult>(Func<Task, TResult> continuation) {
+            return null;
+        }
+
         public Task ContinueWith(Action<Task> continuation) {
             return null;
         }
@@ -85,6 +89,10 @@ public T Result {
             }
         }
 
+        public Task<TResult> ChangeWith<TResult>(Func<Task<T>, TResult> continuation) {
+            return null;
+        }
+
         public Task<T> ContinueWith(Action<Task<T>> continuation) {
             return null;
         }

src/Core/Scripts/Runtime/Task.js

@@ -1,7 +1,7 @@
 // Task
 
 function Task(result) {
-  this._continuations = isValue(result) ?
+  this._continuations = result !== undefined ?
                           (this.status = 'done', null) :
                           (this.status = 'pending', []);
   this.result = result;
@@ -11,6 +11,23 @@ var Task$ = {
   get_completed: function() {
     return this.status != 'pending';
   },
+  changeWith: function(continuation) {
+    var task = new Task();
+    this.continueWith(function(t) {
+      var error = t.error;
+      var result;
+      if (!error) {
+        try {
+          result = continuation(t);
+        }
+        catch (e) {
+          error = e;
+        }
+      }
+      _updateTask(task, result, error);
+    });
+    return task;
+  },
   continueWith: function(continuation) {
     if (this._continuations) {
       this._continuations.push(continuation);

tests/TestCases/Basic/Metadata/Baseline.txt

@@ -3669,6 +3669,11 @@ Types:
                 Visibility: Public, Static
                 Generated Name: any
                 Abstract: False
+            Method: ChangeWith
+                AssociatedType: Task`1
+                Visibility: Public
+                Generated Name: changeWith
+                Abstract: False
             Method: ContinueWith
                 AssociatedType: Task
                 Visibility: Public
@@ -3706,6 +3711,11 @@ Types:
                 AssociatedType: T
                 Visibility: Public
                 Generated Name: result
+            Method: ChangeWith
+                AssociatedType: Task`1
+                Visibility: Public
+                Generated Name: changeWith
+                Abstract: False
             Method: ContinueWith
                 AssociatedType: Task`1
                 Visibility: Public