vue2.7 keep-alive removed component no memory free

[mjsong07]

Version

2.7.12

Reproduction link

github.com

Steps to reproduce

1. npm install
2. npm run serve
3. Open the browser and input the http://localhost:8080/
4. Click the add button to create a1-component.
5. Click the add button to create a2-component.
6. Click the add button to create a3-component.
7. Click the add button to create a4-component .
8. Click the a4-component delete button to remove a4-component

What is expected?

click the a4-component delete button ，I expected the usedJSHeapSize total is 250mb，but it didn't happen.

What is actually happening?

the usedJSHeapSize total still is about 330mb.

---

When you click the add button ,the usedJSHeapSize will increase about 80mb.
click four times ,the usedJSHeapSize total is about 330mb.
next click the a4-component delete button ，the usedJSHeapSize Should be reduce 80mb，expected is about 250mb.
but usedJSHeapSize total still is about 330mb.
you can view operating_steps.gif Steps to reproduce and view memory_analysis.gif to find the memory leak reason.
use the chrome memory tool and analysis report ，We can find The bug because
the a3-component.componentInstance.$vnode.parent.componentOptions.children[0] is a4-component.so the a4-component can not be Memory free.
If you can read chinese ，Open the link for https://juejin.cn/post/7153186266300252168

[mjsong07]

Steps to reproduce

We can find The bug because
the a3-component.componentInstance.$vnode.parent.componentOptions.children[0] is a4-component.so the a4-component can not be Memory free.

[xztl]

问题遇到+1

[mjsong07]

问题遇到+1

看来遇到的人不多，只能换方案去解决了 keepalive的问题 >_<

[vela666]

惊现 面试官

[ning0825]

你好，问题解决了么~

[mjsong07]

你好，问题解决了么~

内存问题没解决，用别的思路规避大量重复创建组件带来的大量内存占用问题。比如共用同一个页签组件不销毁，只是切换data数据。

[DeiviA]

I have the same issue. Any updates on this?

[Sapphire2k]

Any updates on this?

[erlangera]

我推测的主要原因是在 /src/core/components/keep-alive.ts里面清除缓存的方法里面有个判断 if (entry && (!current || entry.tag !== current.tag)) {导致如果要清除的Entry的tag与当前实例tag相同则跳过了强制destroy，个人认为这里应该使用vnode的key进行进一步判断。如 if (entry && (!current || entry.tag !== current.tag || entry.componentInstance.$vnode.key !== current.key)) {

function pruneCacheEntry(
  cache: CacheEntryMap,
  key: string,
  keys: Array<string>,
  current?: VNode
) {
  const entry = cache[key]
  if (entry && (!current || entry.tag !== current.tag)) {
    // @ts-expect-error can be undefined
    entry.componentInstance.$destroy()
  }
  cache[key] = null
  remove(keys, key)
}``` 

[a1mersnow]

I just found that, if you use transition with keep-alive, the issue is more severe.
However, if you only use keep-alive, this commit(which was already released in 2.7.16) is indeed enough to solve the issue.

[xztl]

您好，我已收到您的来信，我会尽快回复您！