feat: Display error if no [...nextauth].js found (#678)

* Display error if no [...nextauth].js found

fixes #647

* Log the error and describe it inside errors.md

Co-authored-by: Balázs Orbán <info@balazsorban.com>

Author: jaknas

src/server/index.js

@@ -32,6 +32,18 @@ async function NextAuth (req, res, userSuppliedOptions) {
     // safe to return and that no more data will be sent.
     const done = resolve
 
+    if (!req.query.nextauth) {
+      const error = 'Cannot find [...nextauth].js in pages/api/auth. Make sure the filename is written correctly.'
+
+      logger.error('MISSING_NEXTAUTH_API_ROUTE_ERROR', error)
+      res
+        .status(500)
+        .end(
+        `Error: ${error}`
+        )
+      return done()
+    }
+
     const { url, query, body } = req
     const {
       nextauth,

www/docs/errors.md

@@ -70,6 +70,7 @@ If you are using a Credentials Provider, NextAuth.js will not persist users or s
 In _most cases_ it does not make sense to specify a database in NextAuth.js options and support a Credentials Provider.
 
 #### CALLBACK_CREDENTIALS_HANDLER_ERROR
+
 ---
 
 ### Session Handling
@@ -127,3 +128,9 @@ They all indicate a problem interacting with the database.
 This error occurs when the Email Authentication Provider is unable to send an email.
 
 Check your mail server configuration.
+
+#### MISSING_NEXTAUTH_API_ROUTE_ERROR
+
+This error happens when `[...nextauth].js` file is not found inside `pages/api/auth`.
+
+Make sure the file is there and the filename is written correctly.