Fix for reviews

- Add docs for clear callback
- Add docs for callback signature
- Add tests for rejected promsie, resolved promise,

Author: hrsh7th

doc/vital/Async/Promise.txt

@@ -381,9 +381,15 @@ on_unhandled_rejection({callback})	*Vital.Async.Promise.on_unhandled_rejection*
 
  	Set callback to catch all unhandled rejected promise's result.
 
+	The {callback} is |Funcref|, it's argument can be unhandled thrown error or unhandled rejected value.
+
 	Note:
 	This callback will called even if you using |Vital.Async.Promise.wait()|.
+	If you want to clear callback, you can use following codes.
 
+>
+	call Promise.on_unhandled_rejection(Promise.noop)
+<
 
 is_promise({value})			*Vital.Async.Promise.is_promise()*
 

test/Async/Promise.vimspec

@@ -806,7 +806,12 @@ Describe Async.Promise
   End
 
   Describe .on_unhandled_rejection
-    It should call when promsie does not catch
+
+    After each
+      call P.on_unhandled_rejection(P.noop)
+    End
+
+    It should call when promise throw error but unhandled
       let l = l:
       call P.on_unhandled_rejection({ result -> extend(l, { 'result': result }) })
 
@@ -816,6 +821,16 @@ Describe Async.Promise
       Assert HasKey(result, 'throwpoint')
     End
 
+    It should call when promise rejected but unhandled
+      let l = l:
+      call P.on_unhandled_rejection({ result -> extend(l, { 'result': result }) })
+
+      let p = P.reject({ 'error': 'error' })
+      call s:wait_has_key(l, 'result')
+      Assert HasKey(result, 'error')
+      Assert Equals(result.error, 'error')
+    End
+
     It should call when promise does not catch with finally
       let l = l:
       call P.on_unhandled_rejection({ result -> extend(l, { 'result': result }) })
@@ -853,6 +868,15 @@ Describe Async.Promise
       call P.wait(Wait(100))
       Assert KeyNotExists(l, 'result')
     End
+
+    It should not call when promise does not throw error
+      let l = l:
+      call P.on_unhandled_rejection({ result -> extend(l, { 'result': result }) })
+
+      let p = P.resolve().then({ -> { 'success': 'success' } })
+      call P.wait(Wait(100))
+      Assert KeyNotExists(l, 'result')
+    End
   End
 End