FirebaseError: "projectId" not provided in firebase.initializeApp (NextJS) - firebase

Question

I'm building a web app with NextJS, NextAuth and Firebase/Firestore, and I'm getting an error:
error - [FirebaseError: "projectId" not provided in firebase.initializeApp.] {
code: 'invalid-argument',
customData: undefined,
toString: [Function (anonymous)]
This is my JS file:
import NextAuth from "next-auth/next";
import TwitterProvider from "next-auth/providers/twitter";
import { FirestoreAdapter } from "#next-auth/firebase-adapter";
import { initializeApp, getApp, getApps } from "firebase/app";
import "firebase/auth";
import { getFirestore, collection, addDoc, getDocs } from "firebase/firestore";
// import { getAnalytics } from "firebase/analytics";
// import { getStorage } from "firebase/storage";
import nextConfig from "next.config";
const firebaseConfig = {
apiKey: nextConfig.env.FIREBASE_API_KEY,
authDomain: nextConfig.env.FIREBASE_AUTH_DOMAIN,
projectId: nextConfig.env.FIREBASE_PROJECT_ID,
storageBucket: nextConfig.env.FIREBASE_STORAGE_BUCKET,
messagingSenderId: nextConfig.env.FIREBASE_MESSAGING_SENDER_ID,
appId: nextConfig.env.FIREBASE_APP_ID,
measurementId: nextConfig.env.FIREBASE_MEASUREMENT_ID,
};
const app = !getApps().length ? initializeApp(firebaseConfig) : getApp();
//const analytics = getAnalytics(app);
const db = getFirestore(app);
//const storage = getStorage(app);
const dbInstance = collection(db, "bugs");
const getBugs = () => {
getDocs(dbInstance).then((data) => {
console.log(data);
});
};
export default NextAuth({
providers: [
TwitterProvider({
clientId: nextConfig.env.TWITTER_CLIENT_ID,
clientSecret: nextConfig.env.TWITTER_CLIENT_SECRET,
version: "2.0", // opt-in to Twitter OAuth 2.0
}),
],
adapter: FirestoreAdapter(db),
});
I can't find any solution on the internet.
Any idea?

Answer 1

In Nextjs, environment variables are only available in the Node.js environment by default, meaning they won't be exposed to the browser.
In order to expose a variable to the browser you have to prefix the variable with NEXT_PUBLIC_
Change your firebase config as shown below and also change the firebase env variables in the .env file to use NEXT_PUBLIC_ prefix.
const firebaseConfig = {
apiKey: process.env.NEXT_PUBLIC_FIREBASE_API_KEY,
authDomain: process.env.NEXT_PUBLIC_FIREBASE_AUTH_DOMAIN,
projectId: process.env.NEXT_PUBLIC_FIREBASE_PROJECT_ID,
storageBucket: process.env.NEXT_PUBLIC_FIREBASE_STORAGE_BUCKET,
messagingSenderId: process.env.NEXT_PUBLIC_FIREBASE_MESSAGING_SENDER_ID,
appId:process.env.NEXT_PUBLIC_FIREBASE_APP_ID,
measurementId: process.env.NEXT_PUBLIC_FIREBASE_MEASUREMENT_ID,
};