The tree function of the [Bug Report] table component hides the child nodes of the tree when new nodes are added, as shown in the figure.

[luoshu-open]

Element UI version

2.7.0

OS/Browsers version

win10/chrome71

Vue version

2.6.10

Reproduction Link

https://user-images.githubusercontent.com/18377791/55374933-d2876c80-553c-11e9-866c-fc4304908286.gif

Steps to reproduce

创建一个table组件，使用树表格，使用element 2.7.0，在新增树节点时，已展开的树，会直接关闭掉。详情见下在的gif图
https://user-images.githubusercontent.com/18377791/55374933-d2876c80-553c-11e9-866c-fc4304908286.gif

What is Expected?

期待的行为：新增节点后，原来展开的树，依然展开，不需要合起来

What is actually happening?

实际行为：新增节点时，已展开的内容会关闭掉

[element-bot]

Translation of this issue:

Element UI version

2.7.0

OS/Browsers version

Win10/chrome71

Vue version

2.6.10

Reproduction Link

https://user-images.githubusercontent.com/18377791/55374933-d2876c80-553c-11e9-866c-fc4304908286.gif

Steps to reproduce

Create a table component, use tree tables, use element 2.7.0, when adding tree nodes, the expanded tree will be closed directly. See the GIF chart below for details.

Https://user-images.githubusercontent.com/18377791/55374933-d2876c80-553c-11e9-866c-fc4304908286.gif

What is Expected?

Expected Behavior: When new nodes are added, the trees that were originally deployed are still deployed and do not need to be closed.

What is actually happening?

Actual behavior: When new nodes are added, expanded content is closed

[luoshu-open]

[hytcwangkai]

知道怎么默认展开树嘛，大佬

[yifire]

展开树的子节点，如何自定义操作的按钮？
Expand the child nodes of the tree, how to customize the button of the operation？

[ziyoung]

see #15170

[ziyoung]

2.9 会支持该功能。