fix(bundler-vite): fix regression of vite options merging (close #1184)

packages/bundler-vite/src/resolveViteConfig.ts

@@ -1,6 +1,6 @@
 import { default as vuePlugin } from '@vitejs/plugin-vue'
 import type { App } from '@vuepress/core'
-import type { InlineConfig } from 'vite'
+import { type InlineConfig, mergeConfig } from 'vite'
 import {
   constantsReplacementPlugin,
   mainPlugin,
@@ -19,18 +19,22 @@ export const resolveViteConfig = async ({
   isBuild: boolean
   isServer: boolean
 }): Promise<InlineConfig> => {
-  return {
-    clearScreen: false,
-    configFile: false,
-    logLevel: !isBuild || app.env.isDebug ? 'info' : 'warn',
-    esbuild: {
-      charset: 'utf8',
+  return mergeConfig(
+    {
+      clearScreen: false,
+      configFile: false,
+      logLevel: !isBuild || app.env.isDebug ? 'info' : 'warn',
+      esbuild: {
+        charset: 'utf8',
+      },
+      plugins: [
+        vuePlugin(options.vuePluginOptions),
+        constantsReplacementPlugin(app),
+        mainPlugin({ app, isBuild, isServer }),
+        userConfigPlugin(options),
+      ],
     },
-    plugins: [
-      vuePlugin(options.vuePluginOptions),
-      constantsReplacementPlugin(app),
-      mainPlugin({ app, isBuild, isServer }),
-      userConfigPlugin(options),
-    ],
-  }
+    // some vite options would not take effect inside a plugin, so we still need to merge them here in addition to userConfigPlugin
+    options.viteOptions ?? {}
+  )
 }