feat(extension): get exception stacks on promise error (#630)

pkg/download/engine/engine.go

@@ -178,7 +178,15 @@ func resolveResult(value goja.Value) (any, error) {
 			if err, ok := p.Result().Export().(error); ok {
 				return nil, err
 			} else {
-				return nil, errors.New(p.Result().String())
+				stack := p.Result().String()
+				result := p.Result()
+				if ro, ok := result.(*goja.Object); ok {
+					stackVal := ro.Get("stack")
+					if stackVal != nil && stackVal.String() != "" {
+						stack = stackVal.String()
+					}
+				}
+				return nil, errors.New(stack)
 			}
 		}
 	}