From 7c989fcc682cefcc723fff01c1d3448c038d604c Mon Sep 17 00:00:00 2001
From: Matias Capeletto <matias.capeletto@gmail.com>
Date: Thu, 26 Nov 2020 07:03:51 +0100
Subject: [PATCH] feat: add $title and $description computed globals

---
 docs/guide/global-computed.md |  8 ++++++++
 src/client/app/index.ts       | 12 ++++++++++++
 src/node/markdownToVue.ts     | 20 +++++++++++++++++++-
 types/shared.d.ts             |  1 +
 4 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/docs/guide/global-computed.md b/docs/guide/global-computed.md
index 4d2eac0d..80bc190f 100644
--- a/docs/guide/global-computed.md
+++ b/docs/guide/global-computed.md
@@ -55,6 +55,14 @@ Reference of [\$page](#page).frontmatter.
 }
 ```
 
+## \$title
+
+Value of the `<title>` label used for the current page.
+
+## \$description
+
+The content value of the `<meta name= "description" content= "...">` for the current page.
+
 ## \$themeConfig
 
 Refers to `$site.themeConfig`.
diff --git a/src/client/app/index.ts b/src/client/app/index.ts
index 847e5e70..0bfc2409 100644
--- a/src/client/app/index.ts
+++ b/src/client/app/index.ts
@@ -92,6 +92,18 @@ export function createApp() {
         return router.route.data.frontmatter
       }
     },
+    $title: {
+      get() {
+        return router.route.data.title || siteDataByRouteRef.value.title
+      }
+    },
+    $description: {
+      get() {
+        return (
+          router.route.data.description || siteDataByRouteRef.value.description
+        )
+      }
+    },
     $themeConfig: {
       get() {
         return siteDataByRouteRef.value.themeConfig
diff --git a/src/node/markdownToVue.ts b/src/node/markdownToVue.ts
index 34594d60..8047a43a 100644
--- a/src/node/markdownToVue.ts
+++ b/src/node/markdownToVue.ts
@@ -3,7 +3,7 @@ import matter from 'gray-matter'
 import LRUCache from 'lru-cache'
 import { createMarkdownRenderer, MarkdownOptions } from './markdown/markdown'
 import { deeplyParseHeader } from './utils/parseHeader'
-import { PageData } from '../../types/shared'
+import { PageData, HeadConfig } from '../../types/shared'
 
 const debug = require('debug')('vitepress:md')
 const cache = new LRUCache<string, MarkdownCompileResult>({ max: 1024 })
@@ -41,6 +41,7 @@ export function createMarkdownToVueRenderFn(
     // inject page data
     const pageData: PageData = {
       title: inferTitle(frontmatter, content),
+      description: inferDescription(frontmatter),
       frontmatter,
       headers: data.headers,
       relativePath: file.replace(/\\/g, '/'),
@@ -101,3 +102,20 @@ const inferTitle = (frontmatter: any, content: string) => {
   }
   return ''
 }
+
+const inferDescription = (frontmatter: Record<string, any>) => {
+  return getHeadMetaContent(frontmatter.head, 'description') || ''
+}
+
+const getHeadMetaContent = (
+  head: HeadConfig[],
+  name: string
+): string | undefined => {
+  if (!head || !head.length) {
+    return undefined
+  }
+  const meta = head.find(([tag, attrs = {}]) => {
+    return tag === 'meta' && attrs.name === name && attrs.content
+  })
+  return meta && meta[1].content
+}
diff --git a/types/shared.d.ts b/types/shared.d.ts
index 859176f2..df809e41 100644
--- a/types/shared.d.ts
+++ b/types/shared.d.ts
@@ -25,6 +25,7 @@ export type HeadConfig =
 
 export interface PageData {
   title: string
+  description: string
   frontmatter: Record<string, any>
   headers: Header[]
   relativePath: string