feat($core): theme entry file as plugin.

Author: ulivz

packages/@vuepress/core/lib/prepare/AppContext.js

@@ -106,6 +106,7 @@ module.exports = class AppContext {
     this.pluginAPI
       // internl core plugins
       .use(Object.assign({}, siteConfig, { name: '@vuepress/internal-site-config' }))
+      .use(Object.assign({}, this.themeEntryFile, { name: '@vuepress/internal-theme-entry-file' }))
       .use(require('../internal-plugins/siteData'))
       .use(require('../internal-plugins/routes'))
       .use(require('../internal-plugins/rootMixins'))
@@ -161,7 +162,7 @@ module.exports = class AppContext {
    *
    *   1. siteConfig.devTemplate
    *   2. `dev.html` located at .vuepress/templates
-   *   3. themeIndexFile.devTemplate
+   *   3. themeEntryFile.devTemplate
    *   4. default devTemplate
    *
    * @api private
@@ -174,7 +175,7 @@ module.exports = class AppContext {
     const siteSsrTemplate2 = path.resolve(templateDir, 'dev.html')
     const siteDevTemplate2 = path.resolve(templateDir, 'ssr.html')
 
-    const { themeSsrTemplate, themeDevTemplate } = this.themeIndexFile
+    const { themeSsrTemplate, themeDevTemplate } = this.themeEntryFile
 
     const defaultSsrTemplate = path.resolve(__dirname, '../app/index.ssr.html')
     const defaultDevTemplate = path.resolve(__dirname, '../app/index.dev.html')

packages/@vuepress/core/lib/prepare/loadTheme.js

@@ -36,7 +36,7 @@ module.exports = async function loadTheme (theme, sourceDir, vuepressDir) {
     (fs.readdirSync(localThemePath)).length > 0
 
   let themePath = null         // Mandatory
-  let themeIndexFile = null    // Optional
+  let themeEntryFile = null    // Optional
   let themeName
   let themeShortcut
 
@@ -58,16 +58,16 @@ module.exports = async function loadTheme (theme, sourceDir, vuepressDir) {
   }
 
   try {
-    themeIndexFile = require(themePath)
+    themeEntryFile = require(themePath)
   } catch (error) {
-    themeIndexFile = {}
+    themeEntryFile = {}
   }
 
   // handle theme api
   const {
     plugins: themePlugins,
     palette: themePalette
-  } = themeIndexFile
+  } = themeEntryFile
 
   const layoutDirs = [
     path.resolve(themePath, 'layouts'),
@@ -132,7 +132,7 @@ module.exports = async function loadTheme (theme, sourceDir, vuepressDir) {
   return {
     themePath,
     layoutComponentMap,
-    themeIndexFile,
+    themeEntryFile,
     themePlugins,
     themePalette,
     themeName,