function patchVnode()

in views/vue.js [6098:6167]
61 lines of code
29 McCabe index (conditional complexity)

    function patchVnode(oldVnode, vnode, insertedVnodeQueue, removeOnly) {
      if (oldVnode === vnode) {
        return;
      }

      const elm = (vnode.elm = oldVnode.elm);

      if (isTrue(oldVnode.isAsyncPlaceholder)) {
        if (isDef(vnode.asyncFactory.resolved)) {
          hydrate(oldVnode.elm, vnode, insertedVnodeQueue);
        } else {
          vnode.isAsyncPlaceholder = true;
        }
        return;
      }

      // reuse element for static trees.
      // note we only do this if the vnode is cloned -
      // if the new node is not cloned it means the render functions have been
      // reset by the hot-reload-api and we need to do a proper re-render.
      if (
        isTrue(vnode.isStatic) &&
        isTrue(oldVnode.isStatic) &&
        vnode.key === oldVnode.key &&
        (isTrue(vnode.isCloned) || isTrue(vnode.isOnce))
      ) {
        vnode.componentInstance = oldVnode.componentInstance;
        return;
      }

      let i;
      const data = vnode.data;
      if (isDef(data) && isDef((i = data.hook)) && isDef((i = i.prepatch))) {
        i(oldVnode, vnode);
      }

      const oldCh = oldVnode.children;
      const ch = vnode.children;
      if (isDef(data) && isPatchable(vnode)) {
        for (i = 0; i < cbs.update.length; ++i) {
          cbs.update[i](oldVnode, vnode);
        }
        if (isDef((i = data.hook)) && isDef((i = i.update))) {
          i(oldVnode, vnode);
        }
      }
      if (isUndef(vnode.text)) {
        if (isDef(oldCh) && isDef(ch)) {
          if (oldCh !== ch) {
            updateChildren(elm, oldCh, ch, insertedVnodeQueue, removeOnly);
          }
        } else if (isDef(ch)) {
          if (isDef(oldVnode.text)) {
            nodeOps.setTextContent(elm, "");
          }
          addVnodes(elm, null, ch, 0, ch.length - 1, insertedVnodeQueue);
        } else if (isDef(oldCh)) {
          removeVnodes(elm, oldCh, 0, oldCh.length - 1);
        } else if (isDef(oldVnode.text)) {
          nodeOps.setTextContent(elm, "");
        }
      } else if (oldVnode.text !== vnode.text) {
        nodeOps.setTextContent(elm, vnode.text);
      }
      if (isDef(data)) {
        if (isDef((i = data.hook)) && isDef((i = i.postpatch))) {
          i(oldVnode, vnode);
        }
      }
    }