test: Add a test for themes from dependencies using Layout.vue as entry point

Author: ocavue

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

@@ -56,17 +56,7 @@ module.exports = function loadTheme (ctx) {
 function normalizeThemePath (resolved) {
   const { entry, name, fromDep } = resolved
   if (fromDep) {
-    const packageRoot = require.resolve(`${name}/package.json`)
-    const { main } = require(packageRoot)
-    if (main.endsWith('.vue')) {
-      // For those cases that "main" field is set to an non-index file
-      // e.g. `layouts/Layout.vue`
-      return packageRoot
-    } else {
-      // For those cases that "index.js" is not at package root
-      // e.g. `lib/index.js` (#1362)
-      return parse(require.resolve(name)).dir
-    }
+    return parse(require.resolve(name)).dir
   } else if (entry.endsWith('.js') || entry.endsWith('.vue')) {
     return parse(entry).dir
   } else {
@@ -97,6 +87,8 @@ function resolveTheme (ctx, resolver, ignoreLocal, theme) {
     // 2. From dep
   } else if (isString(theme)) {
     const resolved = resolver.resolve(theme, sourceDir)
+    console.log('resolveTheme, theme=', theme, 'sourceDir=', sourceDir, 'resolver=', resolver)
+    console.log('resolved:', resolved)
     if (resolved.entry === null) {
       throw new Error(`Cannot resolve theme: ${theme}.`)
     }