ReactCSSTransitionGroupMixin.less

// Usage:
// .ReactCSSTransitionGroupMixin(
//   {opacity: 0},
//   {opacity: 1},
//   {transition: opacity 300ms linear}
// );
.ReactCSSTransitionGroupMixin(@disabled, @active, @transition) {
  &-enter {
    @disabled();
    &-active {
      @active();
      @transition();
    }
  }
  &-leave {
    @active();
    &-active {
      @disabled();
      @transition();
    }
  }
}