customize sidebar group comp & resolve issue with expanding groups

docs/.vuepress/theme/components/SidebarGroup.vue

@@ -0,0 +1,141 @@
+<template>
+  <section
+    class="sidebar-group"
+    :class="[
+      {
+        collapsable,
+        'is-sub-group': depth !== 0
+      },
+      `depth-${depth}`
+    ]"
+  >
+    <RouterLink
+      v-if="item.path"
+      class="sidebar-heading clickable"
+      :class="{
+        open,
+        'active': isActive($route, item.path)
+      }"
+      :to="item.path"
+      @click.native="$emit('toggle')"
+    >
+      <span>{{ item.title }}</span>
+      <span
+        v-if="collapsable"
+        class="arrow"
+        :class="open ? 'down' : 'right'"
+      />
+    </RouterLink>
+
+    <p
+      v-else
+      class="sidebar-heading"
+      :class="{ open }"
+      @click="$emit('toggle')"
+    >
+      <span>{{ item.title }}</span>
+      <span
+        v-if="collapsable"
+        class="arrow"
+        :class="open ? 'down' : 'right'"
+      />
+    </p>
+
+    <DropdownTransition>
+      <SidebarLinks
+        v-if="open || !collapsable || isActive($route, item.path)"
+        class="sidebar-group-items"
+        :items="item.children"
+        :sidebar-depth="item.sidebarDepth"
+        :initial-open-group-index="item.initialOpenGroupIndex"
+        :depth="depth + 1"
+      />
+    </DropdownTransition>
+  </section>
+</template>
+
+<script>
+import { isActive } from '@parent-theme/util'
+import DropdownTransition from '@parent-theme/components/DropdownTransition.vue'
+
+export default {
+  name: 'SidebarGroup',
+
+  components: {
+    DropdownTransition
+  },
+
+  props: [
+    'item',
+    'open',
+    'collapsable',
+    'depth'
+  ],
+
+  // ref: https://vuejs.org/v2/guide/components-edge-cases.html#Circular-References-Between-Components
+  beforeCreate () {
+    this.$options.components.SidebarLinks = require('@theme/components/SidebarLinks.vue').default
+  },
+
+  methods: { isActive }
+}
+</script>
+
+<style lang="stylus">
+.sidebar-group
+  .sidebar-group
+    padding-left 0.5em
+  &:not(.collapsable)
+    .sidebar-heading:not(.clickable)
+      cursor auto
+      color inherit
+  // refine styles of nested sidebar groups
+  &.is-sub-group
+    padding-left 0
+    & > .sidebar-heading
+      font-size 0.95em
+      line-height 1.4
+      font-weight normal
+      padding-left 2rem
+      &:not(.clickable)
+        opacity 0.5
+    & > .sidebar-group-items
+      padding-left 1rem
+      & > li > .sidebar-link
+        font-size: 0.95em;
+        border-left none
+  &.depth-2
+    & > .sidebar-heading
+      border-left none
+
+.sidebar-heading
+  color $textColor
+  transition color .15s ease
+  cursor pointer
+  font-size 1.1em
+  font-weight bold
+  // text-transform uppercase
+  padding 0.35rem 1.5rem 0.35rem 1.25rem
+  width 100%
+  box-sizing border-box
+  margin 0
+  border-left 0.25rem solid transparent
+  &.open, &:hover
+    color inherit
+  .arrow
+    position relative
+    top -0.12em
+    left 0.5em
+  &.clickable
+    &.active
+      font-weight 600
+      color $accentColor
+      border-left-color $accentColor
+    &:hover
+      color $accentColor
+
+.sidebar-group-items
+  transition height .1s ease-out
+  font-size 0.95em
+  overflow hidden
+</style>

docs/.vuepress/theme/components/SidebarLinks.vue

@@ -0,0 +1,106 @@
+<template>
+  <ul
+    v-if="items.length"
+    class="sidebar-links"
+  >
+    <li
+      v-for="(item, i) in items"
+      :key="i"
+    >
+      <SidebarGroup
+        v-if="item.type === 'group'"
+        :item="item"
+        :open="i === openGroupIndex"
+        :collapsable="item.collapsable || item.collapsible"
+        :depth="depth"
+        @toggle="toggleGroup(i)"
+      />
+      <SidebarLink
+        v-else
+        :sidebar-depth="sidebarDepth"
+        :item="item"
+      />
+    </li>
+  </ul>
+</template>
+
+<script>
+import SidebarGroup from '@theme/components/SidebarGroup.vue'
+import SidebarLink from '@parent-theme/components/SidebarLink.vue'
+import { isActive } from '@parent-theme/util'
+
+export default {
+  name: 'SidebarLinks',
+
+  components: { SidebarGroup, SidebarLink },
+
+  props: [
+    'items',
+    'depth',  // depth of current sidebar links
+    'sidebarDepth', // depth of headers to be extracted
+    'initialOpenGroupIndex'
+  ],
+
+  data () {
+    return {
+      openGroupIndex: this.initialOpenGroupIndex || 0
+    }
+  },
+
+  watch: {
+    '$route' () {
+      this.refreshIndex()
+    }
+  },
+
+  created () {
+    this.refreshIndex()
+  },
+
+  methods: {
+    refreshIndex () {
+      const index = resolveOpenGroupIndex(
+        this.$route,
+        this.items
+      )
+      if (index > -1) {
+        this.openGroupIndex = index
+      }
+    },
+
+    toggleGroup (index) {
+      this.openGroupIndex = index === this.openGroupIndex ? -1 : index
+    },
+
+    isActive (page) {
+      return isActive(this.$route, page.regularPath)
+    }
+  }
+}
+
+function resolveOpenGroupIndex (route, items) {
+  for (let i = 0; i < items.length; i++) {
+    const item = items[i]
+    if (descendantIsActive(route, item)) {
+      return i
+    }
+  }
+  return -1
+}
+
+function descendantIsActive (route, item) {
+  if (item.type === 'group') {
+    const childIsActive = item.path && isActive(route, item.path)
+    const grandChildIsActive = item.children.some(child => {
+      if (child.type === 'group') {
+        return descendantIsActive(route, child)
+      } else {
+        return child.type === 'page' && isActive(route, child.path)
+      }
+    })
+
+    return childIsActive || grandChildIsActive
+  }
+  return false
+}
+</script>