fix: ensure using the same markdown config when extracting headers

lib/prepare.js

-const fs = require('fs-extra')
 const path = require('path')
+const fs = require('fs-extra')
 const globby = require('globby')
-const yaml = require('yaml-front-matter')
 const yamlParser = require('js-yaml')
+const yaml = require('yaml-front-matter')
+const createMarkdown = require('./markdown')
 const tempPath = path.resolve(__dirname, 'app/.temp')
 const { inferTitle, extractHeaders } = require('./util')
 
@@ -120,7 +121,8 @@ async function resolveOptions (sourceDir) {
     pagesData: null,
     themePath: null,
     notFoundPath: null,
-    useDefaultTheme
+    useDefaultTheme,
+    markdown: createMarkdown(siteConfig)
   }
 
   if (useDefaultTheme) {
@@ -171,7 +173,11 @@ async function resolveOptions (sourceDir) {
     if (title) {
       data.title = title
     }
-    const headers = extractHeaders(frontmatter.__content, ['h2', 'h3'])
+    const headers = extractHeaders(
+      frontmatter.__content,
+      ['h2', 'h3'],
+      options.markdown
+    )
     if (headers.length) {
       data.headers = headers
     }

lib/util/index.js

@@ -45,9 +45,8 @@ exports.parseFrontmatter = content => {
 
 const LRU = require('lru-cache')
 const cache = LRU({ max: 1000 })
-const md = require('../markdown')()
 
-exports.extractHeaders = (content, include = []) => {
+exports.extractHeaders = (content, include = [], md) => {
   const key = content + include.join(',')
   const hit = cache.get(key)
   if (hit) {

lib/webpack/createBaseConfig.js

@@ -6,9 +6,9 @@ module.exports = function createBaseConfig ({
   outDir,
   publicPath,
   themePath,
-  notFoundPath
+  notFoundPath,
+  markdown
 }, { debug } = {}, isServer) {
-  const markdown = require('../markdown')(siteConfig)
   const Config = require('webpack-chain')
   const { VueLoaderPlugin } = require('vue-loader')
   const CSSExtractPlugin = require('mini-css-extract-plugin')

lib/webpack/markdownLoader.js

@@ -30,7 +30,7 @@ module.exports = function (src) {
 
   if (!isProd && !isServer) {
     const inferredTitle = inferTitle(frontmatter)
-    const headers = extractHeaders(content, ['h2', 'h3'])
+    const headers = extractHeaders(content, ['h2', 'h3'], markdown)
     delete frontmatter.__content
 
     // diff frontmatter and title, since they are not going to be part of the