From 989b810a6c6e04b69e1f429bbbfdc9b0ddb86e66 Mon Sep 17 00:00:00 2001
From: Alena Yuryeva <nimfetrisa@gmail.com>
Date: Mon, 14 Oct 2019 02:20:55 +0300
Subject: [PATCH] src/core/components/keep-alive.js from Vue
 https://github.com/vuejs/vue/blob/215f877/src/core/components/keep-alive.js

---
 keep-alive.js | 124 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 124 insertions(+)
 create mode 100644 keep-alive.js

diff --git a/keep-alive.js b/keep-alive.js
new file mode 100644
index 0000000..fb4cf1e
--- /dev/null
+++ b/keep-alive.js
@@ -0,0 +1,124 @@
+/* @flow */
+
+import { isRegExp, remove } from 'shared/util'
+import { getFirstComponentChild } from 'core/vdom/helpers/index'
+
+type VNodeCache = { [key: string]: ?VNode };
+
+function getComponentName (opts: ?VNodeComponentOptions): ?string {
+  return opts && (opts.Ctor.options.name || opts.tag)
+}
+
+function matches (pattern: string | RegExp | Array<string>, name: string): boolean {
+  if (Array.isArray(pattern)) {
+    return pattern.indexOf(name) > -1
+  } else if (typeof pattern === 'string') {
+    return pattern.split(',').indexOf(name) > -1
+  } else if (isRegExp(pattern)) {
+    return pattern.test(name)
+  }
+  /* istanbul ignore next */
+  return false
+}
+
+function pruneCache (keepAliveInstance: any, filter: Function) {
+  const { cache, keys, _vnode } = keepAliveInstance
+  for (const key in cache) {
+    const cachedNode: ?VNode = cache[key]
+    if (cachedNode) {
+      const name: ?string = getComponentName(cachedNode.componentOptions)
+      if (name && !filter(name)) {
+        pruneCacheEntry(cache, key, keys, _vnode)
+      }
+    }
+  }
+}
+
+function pruneCacheEntry (
+  cache: VNodeCache,
+  key: string,
+  keys: Array<string>,
+  current?: VNode
+) {
+  const cached = cache[key]
+  if (cached && (!current || cached.tag !== current.tag)) {
+    cached.componentInstance.$destroy()
+  }
+  cache[key] = null
+  remove(keys, key)
+}
+
+const patternTypes: Array<Function> = [String, RegExp, Array]
+
+export default {
+  name: 'keep-alive',
+  abstract: true,
+
+  props: {
+    include: patternTypes,
+    exclude: patternTypes,
+    max: [String, Number]
+  },
+
+  created () {
+    this.cache = Object.create(null)
+    this.keys = []
+  },
+
+  destroyed () {
+    for (const key in this.cache) {
+      pruneCacheEntry(this.cache, key, this.keys)
+    }
+  },
+
+  mounted () {
+    this.$watch('include', val => {
+      pruneCache(this, name => matches(val, name))
+    })
+    this.$watch('exclude', val => {
+      pruneCache(this, name => !matches(val, name))
+    })
+  },
+
+  render () {
+    const slot = this.$slots.default
+    const vnode: VNode = getFirstComponentChild(slot)
+    const componentOptions: ?VNodeComponentOptions = vnode && vnode.componentOptions
+    if (componentOptions) {
+      // check pattern
+      const name: ?string = getComponentName(componentOptions)
+      const { include, exclude } = this
+      if (
+        // not included
+        (include && (!name || !matches(include, name))) ||
+        // excluded
+        (exclude && name && matches(exclude, name))
+      ) {
+        return vnode
+      }
+
+      const { cache, keys } = this
+      const key: ?string = vnode.key == null
+        // same constructor may get registered as different local components
+        // so cid alone is not enough (#3269)
+        ? componentOptions.Ctor.cid + (componentOptions.tag ? `::${componentOptions.tag}` : '')
+        : vnode.key
+      if (cache[key]) {
+        vnode.componentInstance = cache[key].componentInstance
+        // make current key freshest
+        remove(keys, key)
+        keys.push(key)
+      } else {
+        cache[key] = vnode
+        keys.push(key)
+        // prune oldest entry
+        if (this.max && keys.length > parseInt(this.max)) {
+          pruneCacheEntry(cache, keys[0], keys, this._vnode)
+        }
+      }
+
+      vnode.data.keepAlive = true
+    }
+    return vnode || (slot && slot[0])
+  }
+}