feat(theme): auto open collapsed sidebar on entering (#1094)

src/client/theme-default/components/VPSidebarGroup.vue

@@ -1,6 +1,8 @@
 <script lang="ts" setup>
 import type { DefaultTheme } from 'vitepress/theme'
 import { ref, watchEffect } from 'vue'
+import { useData } from 'vitepress'
+import { isActive } from '../support/utils'
 import VPIconPlusSquare from './icons/VPIconPlusSquare.vue'
 import VPIconMinusSquare from './icons/VPIconMinusSquare.vue'
 import VPSidebarLink from './VPSidebarLink.vue'
@@ -17,6 +19,13 @@ watchEffect(() => {
   collapsed.value = !!(props.collapsible && props.collapsed)
 })
 
+const { page } = useData()
+watchEffect(() => {
+  if(props.items.some((item) => { return isActive(page.value.relativePath, item.link) })){
+    collapsed.value = false
+  }
+})
+
 function toggle() {
   if (props.collapsible) {
     collapsed.value = !collapsed.value