fix(firebase): add ability to pass in firebase config

docs/docs/adapters/firebase.md

@@ -17,7 +17,7 @@ npm install next-auth @next-auth/firebase-adapter
 
 2. Add this adapter to your `pages/api/auth/[...nextauth].js` next-auth configuration object.
 
-```javascript title="pages/api/auth/[...nextauth].js"
+```typescript title="pages/api/auth/[...nextauth].ts"
 import NextAuth from "next-auth"
 import GoogleProvider from "next-auth/providers/google"
 import { FirestoreAdapter } from "@next-auth/firebase-adapter"
@@ -47,13 +47,38 @@ export default NextAuth({
 });
 ```
 
+Additionally, if you've initialized your app on the client you can pass in the project options:
+
+```typescript title="firebase.ts"
+import { initializeApp } from "firebase/app"
+
+export const firebaseApp = initializeApp({
+  // ...firebase options
+});
+```
+
+```typescript title="pages/api/auth/[...nextauth].ts"
+import NextAuth from "next-auth"
+import { FirestoreAdapter } from "@next-auth/firebase-adapter"
+
+import { firebaseApp } from "../../../firebase"
+
+export default NextAuth({
+  providers: [
+    //...
+  ],
+  adapter: FirestoreAdapter({ ...firebaseApp.options }),
+})
+
+```
+
 ## Options
 
 When initializing the firestore adapter, you must pass in the firebase config object with the details from your project. More details on how to obtain that config object can be found [here](https://support.google.com/firebase/answer/7015592).
 
 An example firebase config looks like this:
 
-```js
+```typescript
 const firebaseConfig = {
   apiKey: "AIzaSyDOCAbC123dEf456GhI789jKl01-MnO",
   authDomain: "myapp-project-123.firebaseapp.com",
@@ -70,7 +95,7 @@ See [firebase.google.com/docs/web/setup](https://firebase.google.com/docs/web/se
 
 You can optionally pass in emulator options to automatically connect to your local Firebase emulator.
 
-```js
+```typescript
 FirestoreAdapter({
   // ...
   // Passing in an enable object will enable the emulator

packages/adapter-firebase/package.json

@@ -43,4 +43,4 @@
     "jest": "^27.4.3",
     "next-auth": "workspace:*"
   }
-}
+}

packages/adapter-firebase/src/firebase-initializer.ts

@@ -0,0 +1,10 @@
+import { getApp, getApps, initializeApp } from "firebase/app"
+import type { FirebaseOptions } from "firebase/app"
+
+export const getFirebaseApp = (options: FirebaseOptions) => {
+  if (getApps().length === 0) {
+    return initializeApp(options)
+  }
+
+  return getApp()
+}

packages/adapter-firebase/src/index.ts

@@ -24,10 +24,11 @@ import type {
 } from "next-auth/adapters"
 
 import { getConverter } from "./converter"
+import { getFirebaseApp } from "./firebase-initializer"
 
 type IndexableObject = Record<string, unknown>
 
-export interface FirestoreAdapterOptions {
+export interface FirestoreAdapterOptions extends FirebaseOptions {
   emulator?: {
     host?: string
     port?: number
@@ -37,8 +38,8 @@ export interface FirestoreAdapterOptions {
 export function FirestoreAdapter({
   emulator,
   ...firebaseOptions
-}: FirebaseOptions & FirestoreAdapterOptions): Adapter {
-  const firebaseApp = initializeApp(firebaseOptions)
+}: FirestoreAdapterOptions): Adapter {
+  const firebaseApp = getFirebaseApp(firebaseOptions)
   const db = getFirestore(firebaseApp)
 
   if (emulator) {

packages/adapter-firebase/tests/index.test.ts

@@ -1,76 +1,118 @@
 import { runBasicTests } from "@next-auth/adapter-test"
 import { FirestoreAdapter } from "../src"
 
-import { getFirestore, connectFirestoreEmulator, terminate, collection, query, where, limit, getDocs, getDoc, doc } from "firebase/firestore"
-import { initializeApp } from "firebase/app";
-import { getConverter } from "../src/converter";
-import type { AdapterSession, AdapterUser, VerificationToken } from "next-auth/adapters";
-import type { Account } from "next-auth";
-
-const app = initializeApp({ projectId: "next-auth-test" });
-const firestore = getFirestore(app);
-
-connectFirestoreEmulator(firestore, 'localhost', 8080);
-
-type IndexableObject = Record<string, unknown>;
-
-const Users = collection(firestore, 'users').withConverter(getConverter<AdapterUser>());
-const Sessions = collection(firestore, 'sessions').withConverter(getConverter<AdapterSession & IndexableObject>());
-const Accounts = collection(firestore, 'accounts').withConverter(getConverter<Account>());
-const VerificationTokens = collection(firestore, 'verificationTokens').withConverter(getConverter<VerificationToken & IndexableObject>({ excludeId: true }));
+import {
+  getFirestore,
+  connectFirestoreEmulator,
+  terminate,
+  collection,
+  query,
+  where,
+  limit,
+  getDocs,
+  getDoc,
+  doc,
+} from "firebase/firestore"
+import { initializeApp } from "firebase/app"
+import { getConverter } from "../src/converter"
+import type {
+  AdapterSession,
+  AdapterUser,
+  VerificationToken,
+} from "next-auth/adapters"
+import type { Account } from "next-auth"
+
+const app = initializeApp({ projectId: "next-auth-test" })
+const firestore = getFirestore(app)
+
+connectFirestoreEmulator(firestore, "localhost", 8080)
+
+type IndexableObject = Record<string, unknown>
+
+const Users = collection(firestore, "users").withConverter(
+  getConverter<AdapterUser>()
+)
+const Sessions = collection(firestore, "sessions").withConverter(
+  getConverter<AdapterSession & IndexableObject>()
+)
+const Accounts = collection(firestore, "accounts").withConverter(
+  getConverter<Account>()
+)
+const VerificationTokens = collection(
+  firestore,
+  "verificationTokens"
+).withConverter(
+  getConverter<VerificationToken & IndexableObject>({ excludeId: true })
+)
 
 runBasicTests({
   adapter: FirestoreAdapter({ projectId: "next-auth-test" }),
   db: {
     async disconnect() {
-      await terminate(firestore);
+      await terminate(firestore)
     },
     async session(sessionToken) {
-      const snapshotQuery = query(Sessions, where("sessionToken", "==", sessionToken), limit(1));
-      const snapshots = await getDocs(snapshotQuery);
-      const snapshot = snapshots.docs[0];
+      const snapshotQuery = query(
+        Sessions,
+        where("sessionToken", "==", sessionToken),
+        limit(1)
+      )
+      const snapshots = await getDocs(snapshotQuery)
+      const snapshot = snapshots.docs[0]
 
       if (snapshot?.exists() && Sessions.converter) {
-        const session = Sessions.converter.fromFirestore(snapshot);
+        const session = Sessions.converter.fromFirestore(snapshot)
 
-        return session;
+        return session
       }
 
-      return null;
+      return null
     },
     async user(id) {
-      const snapshot = await getDoc(doc(Users, id));
+      const snapshot = await getDoc(doc(Users, id))
 
       if (snapshot?.exists() && Users.converter) {
-        const user = Users.converter.fromFirestore(snapshot);
+        const user = Users.converter.fromFirestore(snapshot)
 
-        return user;
+        return user
       }
 
-      return null;
+      return null
     },
     async account({ provider, providerAccountId }) {
-      const snapshotQuery = query(Accounts, where("provider", "==", provider), where("providerAccountId", "==", providerAccountId), limit(1));
-      const snapshots = await getDocs(snapshotQuery);
-      const snapshot = snapshots.docs[0];
+      const snapshotQuery = query(
+        Accounts,
+        where("provider", "==", provider),
+        where("providerAccountId", "==", providerAccountId),
+        limit(1)
+      )
+      const snapshots = await getDocs(snapshotQuery)
+      const snapshot = snapshots.docs[0]
 
       if (snapshot?.exists() && Accounts.converter) {
-        const account = Accounts.converter.fromFirestore(snapshot);
+        const account = Accounts.converter.fromFirestore(snapshot)
 
-        return account;
+        return account
       }
 
-      return null;
+      return null
     },
     async verificationToken({ identifier, token }) {
-      const snapshotQuery = query(VerificationTokens, where("identifier", "==", identifier), where("token", "==", token), limit(1));
-      const snapshots = await getDocs(snapshotQuery);
-      const snapshot = snapshots.docs[0];
+      const snapshotQuery = query(
+        VerificationTokens,
+        where("identifier", "==", identifier),
+        where("token", "==", token),
+        limit(1)
+      )
+      const snapshots = await getDocs(snapshotQuery)
+      const snapshot = snapshots.docs[0]
 
       if (snapshot?.exists() && VerificationTokens.converter) {
-        const verificationToken = VerificationTokens.converter.fromFirestore(snapshot);
+        const verificationToken = VerificationTokens.converter.fromFirestore(
+          snapshot
+        )
 
-        return verificationToken;
+        return verificationToken
       }
     },
   },