feat(client): introduce NEXTAUTH_URL_INTERNAL (#1449)

Co-authored-by: @gergelyke

src/client/index.d.ts

@@ -29,6 +29,8 @@ type GetSession<S extends Record<string, unknown> = DefaultSession> = (options:
 export interface NextAuthConfig {
   baseUrl: string
   basePath: string
+  baseUrlServer: string
+  basePathServer: string
   /** 0 means disabled (don't send); 60 means send every 60 seconds */
   keepAlive: number
   /** 0 means disabled (only use cache); 60 means sync if last checked > 60 seconds ago */

src/client/index.js

@@ -22,6 +22,8 @@ import parseUrl from '../lib/parse-url'
 const __NEXTAUTH = {
   baseUrl: parseUrl(process.env.NEXTAUTH_URL || process.env.VERCEL_URL).baseUrl,
   basePath: parseUrl(process.env.NEXTAUTH_URL).basePath,
+  baseUrlServer: parseUrl(process.env.NEXTAUTH_URL_INTERNAL || process.env.NEXTAUTH_URL || process.env.VERCEL_URL).baseUrl,
+  basePathServer: parseUrl(process.env.NEXTAUTH_URL_INTERNAL || process.env.NEXTAUTH_URL).basePath,
   keepAlive: 0,
   clientMaxAge: 0,
   // Properties starting with _ are used for tracking internal app state
@@ -359,7 +361,7 @@ function _apiBaseUrl () {
     }
 
     // Return absolute path when called server side
-    return `${__NEXTAUTH.baseUrl}${__NEXTAUTH.basePath}`
+    return `${__NEXTAUTH.baseUrlServer}${__NEXTAUTH.basePathServer}`
   }
   // Return relative path when called client side
   return __NEXTAUTH.basePath

www/docs/configuration/options.md

@@ -21,6 +21,14 @@ _e.g. `NEXTAUTH_URL=https://example.com/custom-route/api/auth`_
 To set environment variables on Vercel, you can use the [dashboard](https://vercel.com/dashboard) or the `now env` command.
 :::
 
+### NEXTAUTH_URL_INTERNAL
+
+If provided, server-side calls will use this instead of `NEXTAUTH_URL`. Useful in environments when the server doesn't have access to the canonical URL of your site. Defaults to `NEXTAUTH_URL`.
+
+```
+NEXTAUTH_URL_INTERNAL=http://10.240.8.16
+```
+
 ---
 
 ## Options