fix(plugin-legacy): dynamic import browserslist-to-esbuild (#16011)

Author: bluwy

packages/plugin-legacy/src/index.ts

@@ -24,7 +24,6 @@ import type {
 } from '@babel/core'
 import colors from 'picocolors'
 import browserslist from 'browserslist'
-import browserslistToEsbuild from 'browserslist-to-esbuild'
 import type { Options } from './types'
 import {
   detectModernBrowserCode,
@@ -189,7 +188,7 @@ function viteLegacyPlugin(options: Options = {}): Plugin[] {
   const legacyConfigPlugin: Plugin = {
     name: 'vite:legacy-config',
 
-    config(config, env) {
+    async config(config, env) {
       if (env.command === 'build' && !config.build?.ssr) {
         if (!config.build) {
           config.build = {}
@@ -209,9 +208,16 @@ function viteLegacyPlugin(options: Options = {}): Plugin[] {
           // See https://github.com/vitejs/vite/pull/10052#issuecomment-1242076461
           overriddenBuildTarget = config.build.target !== undefined
           overriddenDefaultModernTargets = options.modernTargets !== undefined
-          config.build.target = options.modernTargets
-            ? browserslistToEsbuild(options.modernTargets)
-            : modernTargetsEsbuild
+
+          if (options.modernTargets) {
+            // Package is ESM only
+            const { default: browserslistToEsbuild } = await import(
+              'browserslist-to-esbuild'
+            )
+            config.build.target = browserslistToEsbuild(options.modernTargets)
+          } else {
+            config.build.target = modernTargetsEsbuild
+          }
         }
       }