解決nextjs部署到now上之後出現的“Unable to import module 'now__launcher'”錯誤

這個錯誤是由於在next.config.js中直接引用了withLess之類的外掛導致的。在now環境下require外掛需要在PHASE_PRODUCTION_SERVER階段下，如果不加這個階段的判斷就會報錯。

這個是錯誤的做法

// ❌ Don't put this here

const withCSS = require('@zeit/next-css'); // 由於不在PHASE_PRODUCTION_SERVER階段所以報錯

const { PHASE_PRODUCTION_SERVER } 
 
=

  process.env.NODE_ENV === 'development'

    ? {}

    : !process.env.NOW_REGION

      ? require('next/constants')

      : require('next-server/constants');

module.exports = (phase, { defaultConfig }) => {

  if (phase === PHASE_PRODUCTION_SERVER) {

    // Config used to run in production.

    return
 
 {};

  }

 

  return withCSS();

};

正確的寫法：

const { PHASE_PRODUCTION_SERVER } =

  process.env.NODE_ENV === 'development'

    ? {}

    : !process.env.NOW_REGION

      ? require('next/constants')

      : require('next-server/constants');

module.exports = (phase, { defaultConfig }) => {

  
 
if (phase === PHASE_PRODUCTION_SERVER) {

    // Config used to run in production.

    return {};

  }

 

  // ✅ Put the require call here.

  const withCSS = require('@zeit/next-css');

 

  return withCSS();

};

參考：https://github.com/zeit/next.js/issues/5750