Custom file path option for next.config.js file through CLI commands

[amir-zahedi]

Describe the feature you'd like to request

When abstracting nextJS configs (say in the case of a multi nextJS app mono repo) it can be helpful if one could share a single config file between them. This requires the cli to expose an option for a custom config file path instead of (as I understand it) only being able to customise nextJS configs through a next.config.js file sitting at the app root.

Describe the solution you'd like

Add support for a -config option or equivalent for cli commands
next dev -config [CUSTOM CONFIG FILE PATH]
next build -config [CUSTOM CONFIG FILE PATH]
next start -config [CUSTOM CONFIG FILE PATH]

Describe alternatives you've considered

One possible viable alternative I tried is Importing shared config into each apps next/config.js that is not the most elegant solution but also in my case failed with Cannot use import statement outside a module because all our configs leave in an external npm package.

[yassernasc]

I was seeking this path option for config files but for another use case besides "merge shared configs". At each config file I would like to use exportPathMap to filter pages based on its context. Eg. next.config.app.js, next.config.blog.js, next.config.admin.js.

This would be a very simple "monorepo", reusing components and package configurations (eslint, tailwind, jest, ..) and just filtering pages at export time.

[tholder]

Agree. You should be able to specify next config on command line. We are trying to manage multiple projects from the same code base and each needs a separate config.

[lake2]

any updates?

[xiamu14]

any updates?

[wfl-junior]

+1 I want this as well

[riosant]

Did you find any solution?

[gaojude]

any updates?

[arvind-iyer-dev]

Can we create an Issue for this ?
I want to be able to set the output field to standalone through CLI
maybe the next build command can have options which override certain fields in the config file.

Or...

We can set an Env variable like how Bundle Analyzer is enabled ? and modify the values through that

[coderfin]

I found a workaround.

I wanted to be able to easily customize the output of my build. Initially I was looking for a way to have different config files but then I thought of environment variables.

I setup my package.json scripts with an environment variable OUTPUT:

...
"scripts": {
  ...
  "build": "next build",
  "export": "OUTPUT=export next build",
  "start": "next start",
  ...
},
...

Then in next.config.mjs:

/** @type {import('next').NextConfig} */
const nextConfig = {
  output: process.env.OUTPUT,
};

export default nextConfig;

You could use a similar strategy to have any number of config objects that are used or ignored based on one or more environment variables.

[coderfin]

I just realized that @arvind-berrybox had the same or similar suggestion... haha.
#31433 (comment)