refactor: integrate isLayoutExists and isPageExists

packages/@vuepress/core/lib/client/components/Content.js

@@ -8,7 +8,7 @@ export default {
   },
   render (h) {
     const pageKey = this.pageKey || this.$parent.$page.key
-    if (this.$vuepress.isPageExists(pageKey)) {
+    if (this.$hasComponent(pageKey)) {
       return h(pageKey)
     }
     return h('')

packages/@vuepress/core/lib/client/components/GlobalLayout.vue

@@ -7,7 +7,7 @@ export default {
   computed: {
     layout () {
       if (this.$page.path) {
-        if (this.$vuepress.isLayoutExists(this.$page.frontmatter.layout)) {
+        if (this.$hasComponent(this.$page.frontmatter.layout)) {
           return this.$page.frontmatter.layout
         }
         return 'Layout'

packages/@vuepress/core/lib/client/plugins/Store.d.ts

@@ -1,15 +1,13 @@
 import Vue from 'Vue'
 
 export declare class Store {
-  store: Vue;
+  store: Vue
 
-  $get(key: string): any;
+  $get(key: string): any
 
-  $set(key: string, value: any): void;
+  $set(key: string, value: any): void
 
-  $emit: typeof Vue.prototype.$emit;
+  $emit: typeof Vue.prototype.$emit
 
-  $on: typeof Vue.prototype.$on;
+  $on: typeof Vue.prototype.$on
 }
-
-

packages/@vuepress/core/lib/client/plugins/VuePress.d.ts

@@ -1,14 +1,8 @@
-import { Store } from './Store';
-import { AsyncComponent } from 'vue'
+import { Store } from './Store'
 
-declare class VuePress extends Store {
-  isPageExists (pageKey: string): boolean;
-
-  isLayoutExists (pageKey: string): boolean;
-}
-
-declare module "vue/types/vue" {
+declare module 'vue/types/vue' {
   export interface Vue {
-    $vuepress: VuePress;
+    $vuepress: Store
+    $hasComponent (key: string): boolean
   }
 }

packages/@vuepress/core/lib/client/plugins/VuePress.js

@@ -1,4 +1,3 @@
-import Vue from 'vue'
 import Store from './Store'
 
 // TODO: reuse this function in shared-utils
@@ -14,20 +13,11 @@ function cached (fn) {
 
 const pascalize = cached((str = '') => str.replace(/(^|-)\w/g, s => s.slice(-1).toUpperCase()))
 
-class VuePress extends Store {
-  isPageExists (pageKey) {
-    return Boolean(Vue.component(pascalize(pageKey)))
-  }
-
-  isLayoutExists (layout) {
-    return Boolean(Vue.component(pascalize(layout)))
-  }
-}
-
 export default {
   install (Vue) {
-    const ins = new VuePress()
-    Vue.$vuepress = ins
-    Vue.prototype.$vuepress = ins
+    const vuepress = new Store()
+    Vue.$vuepress = vuepress
+    Vue.prototype.$vuepress = vuepress
+    Vue.prototype.$hasComponent = key => Boolean(Vue.component(pascalize(key)))
   }
 }

packages/docs/docs/theme/option-api.md

@@ -111,7 +111,7 @@ export default {
   computed: {
     layout () {
       if (this.$page.path) {
-        if (this.$vuepress.isLayoutExists(this.$frontmatter.layout)) {
+        if (this.$hasComponent(this.$frontmatter.layout)) {
           return this.$frontmatter.layout
         }
         return 'Layout'

packages/docs/docs/zh/theme/option-api.md

@@ -111,7 +111,7 @@ export default {
   computed: {
     layout () {
       if (this.$page.path) {
-        if (this.$vuepress.isLayoutExists(this.$frontmatter.layout)) {
+        if (this.$hasComponent(this.$frontmatter.layout)) {
           return this.$frontmatter.layout
         }
         return 'Layout'