[Bug]: NEXTAUTH_URL is overridden

[phbernard]

Summary

Because the plugin supports NextAuth.js, it sets NEXTAUTH_URL automatically at deploy.

However, it does so every time, even when NEXTAUTH_URL is already explicitly initialized as a regular environment variable.

This behavior is misleading. Someone who sets NEXTAUTH_URL and doesn't know about NextAuth.js support has no reason to think NEXTAUTH_URL will be changed. It also blocks people who need to set NEXTAUTH_URL to a particular value (more about this below).

Suggested change:

• When about to set NEXTAUTH_URL, do nothing when it is already defined.
• Log this particular behavior so people who know about NextAuth.js support are not surprised.

As an aside, why would you want to explicitly set NEXTAUTH_URL? For example in case of multi-domains support. This can be achieved with multiple domains and a middleware. You can find an advanced example of this in the Vercel Platform Starter Kit. A classic setting would be for the app to serve both example.com (+ www.example.com) and app.example.com. As the subdomain suggests, NEXTAUTH_URL will be set to https://app.example.com. Currently, the plugin just doesn't allow it.

Steps to reproduce

I don't think this issue needs any guidance in this respect. The behavior is straightforward and fits in 5 lines of code.

A link to a reproduction repository

No response

Plugin version

@netlify/[email protected] from Netlify app

More information about your build

• I am building using the CLI
• I am building using file-based configuration (netlify.toml)

What OS are you using?

No response

Your netlify.toml file

`netlify.toml`

# Paste content of your `netlify.toml` file here

Your public/_redirects file

`_redirects`

# Paste content of your `_redirects` file here

Your next.config.js file

`next.config.js`

# Paste content of your `next.config.js` file here. Check there is no private info in there.

Builds logs (or link to your logs)

Build logs

# Paste logs here

Function logs

Function logs

# Paste logs here

.next JSON files

generated .next JSON files

# Paste file contents here. Please check there isn't any private info in them
# You can either build locally, or download the deploy from Netlify by clicking the arrow next to the deploy time.

[ericapisani]

@phbernard Thanks so much for reporting this and for the explanation of the use case for explicitly setting the environment variable.

I just merged a PR which should fix this, but if for some reason there's still issues around this functionality feel free to reach out.

[aleehedl]

@ericapisani I was wondering if .env files could be taken into account for this as well? I was still experiencing this bug until I found out from the pull request comments that next.config.js was the right place for setting the user-defined NEXTAUTH_URL. In my case, I write the values to .env file dynamically in the Netlify build step.