render: function render()

in assets/js/vue.js [8735:8845]

• 70 lines of code
• 26 McCabe index (conditional complexity)

    render: function render (h) {
      var this$1 = this;

      var children = this.$slots.default;
      if (!children) {
        return
      }

      // filter out text nodes (possible whitespaces)
      children = children.filter(isNotTextNode);
      /* istanbul ignore if */
      if (!children.length) {
        return
      }

      // warn multiple elements
      if (children.length > 1) {
        warn(
          '<transition> can only be used on a single element. Use ' +
          '<transition-group> for lists.',
          this.$parent
        );
      }

      var mode = this.mode;

      // warn invalid mode
      if (mode && mode !== 'in-out' && mode !== 'out-in'
      ) {
        warn(
          'invalid <transition> mode: ' + mode,
          this.$parent
        );
      }

      var rawChild = children[0];

      // if this is a component root node and the component's
      // parent container node also has transition, skip.
      if (hasParentTransition(this.$vnode)) {
        return rawChild
      }

      // apply transition data to child
      // use getRealChild() to ignore abstract components e.g. keep-alive
      var child = getRealChild(rawChild);
      /* istanbul ignore if */
      if (!child) {
        return rawChild
      }

      if (this._leaving) {
        return placeholder(h, rawChild)
      }

      // ensure a key that is unique to the vnode type and to this transition
      // component instance. This key will be used to remove pending leaving nodes
      // during entering.
      var id = "__transition-" + (this._uid) + "-";
      child.key = child.key == null
        ? child.isComment
          ? id + 'comment'
          : id + child.tag
        : isPrimitive(child.key)
          ? (String(child.key).indexOf(id) === 0 ? child.key : id + child.key)
          : child.key;

      var data = (child.data || (child.data = {})).transition = extractTransitionData(this);
      var oldRawChild = this._vnode;
      var oldChild = getRealChild(oldRawChild);

      // mark v-show
      // so that the transition module can hand over the control to the directive
      if (child.data.directives && child.data.directives.some(isVShowDirective)) {
        child.data.show = true;
      }

      if (
        oldChild &&
        oldChild.data &&
        !isSameChild(child, oldChild) &&
        !isAsyncPlaceholder(oldChild) &&
        // #6687 component root is a comment node
        !(oldChild.componentInstance && oldChild.componentInstance._vnode.isComment)
      ) {
        // replace old child transition data with fresh one
        // important for dynamic transitions!
        var oldData = oldChild.data.transition = extend({}, data);
        // handle transition mode
        if (mode === 'out-in') {
          // return placeholder node and queue update when leave finishes
          this._leaving = true;
          mergeVNodeHook(oldData, 'afterLeave', function () {
            this$1._leaving = false;
            this$1.$forceUpdate();
          });
          return placeholder(h, rawChild)
        } else if (mode === 'in-out') {
          if (isAsyncPlaceholder(child)) {
            return oldRawChild
          }
          var delayedLeave;
          var performLeave = function () { delayedLeave(); };
          mergeVNodeHook(data, 'afterEnter', performLeave);
          mergeVNodeHook(data, 'enterCancelled', performLeave);
          mergeVNodeHook(oldData, 'delayLeave', function (leave) { delayedLeave = leave; });
        }
      }

      return rawChild
    }