Standalone build assetPrefix conditional config

[impaler]

Summary

Trying to set assetPrefix based on a process.env value after a production build, does not seem possible.

Reading, does not mention this value is static and cannot change after the build:

https://nextjs.org/docs/api-reference/next.config.js/cdn-support-with-asset-prefix

It has the example of a conditional use of process.env

const isProd = process.env.NODE_ENV === 'production'

module.exports = {
  // Use the CDN in production and localhost for development.
  assetPrefix: isProd ? 'https://cdn.mydomain.com' : undefined,
}

This led me to believe that it's possible to change this based on another process env, say for instance a custom deployment environment:

module.exports = {
  // eg change via env config on when the server starts
  assetPrefix: process.env.CDN_PATH,
}

Can't get this to work in the production build as the assetPrefix is used in the .next output for various required-server-files.json files and generated html statically.

Anyone know how to set the assetPrefix dynamically, from process.env I am guessing its just not possible from what I can see.

[andorthehood]

If you opt for 'standalone' output when building, your next.config file will be serialised into ./next/standalone/server.js. As of now, a dynamic assetPrefix would be only achievable by using a custom server.

[Mihir-Karbelkar]

Can you point out to a resource for a custom server? Thanks

[moparlakci]

Just do a little string replace on the generated server.js file.

[isbasex]

Next.js official needs to support this feature as soon as possible; it is very necessary.