title: Failed at the functions@ lint script
body: <p>I'm trying to deploy Firebase but i'm getting this error </p>
  
  <blockquote>
    <p>error    Each then() should return a value or throw  promise/always-return</p>
  </blockquote>
  
  <p>this is my code</p>
  
  <pre><code>'use strict'
  
  const functions = require('firebase-functions');
  const admin = require('firebase-admin');
  admin.initializeApp(functions.config().firebase);
  
  
  exports.sendNotification = functions.database.ref('/notifications/{user_id}/{notification_id}').onWrite(event =&gt; {
  
  
  
  
    const user_id = event.params.user_id;
    const notification_id = event.params.notification_id;
  
    console.log('We have a notification from : ', user_id);
  
  
  
    if(!event.data.val()){
  
      return console.log('A Notification has been deleted from the database : ', notification_id);
  
    }
  
  
    const fromUser = admin.database().ref(`/notifications/${user_id}/${notification_id}`).once('value');
  
    return fromUser.then(fromUserResult =&gt; {
  
      const from_user_id = fromUserResult.val().from;
  
      console.log('You have new notification from  : ', from_user_id);
  
  
      const userQuery = admin.database().ref(`Users/${from_user_id}/name`).once('value');
      const deviceToken = admin.database().ref(`/Users/${user_id}/device_token`).once('value');
  
      return Promise.all([userQuery, deviceToken]).then(result =&gt; {
  
        const userName = result[0].val();
        const token_id = result[1].val();
  
  
        const payload = {
          notification: {
            title : "New Friend Request",
            body: `${userName} has sent you request`,
            icon: "default",
            click_action : "in.tvac.akshaye.lapitchat_TARGET_NOTIFICATION"
          },
          data : {
            from_user_id : from_user_id
          }
        };
  
  
  
        return admin.messaging().sendToDevice(token_id, payload).then(response =&gt; {
  
          console.log('This was the notification Feature');
  
        });
  
      });
  
    });
  
  });
  </code></pre>
  
  <p>this is the error log </p>
  
  <blockquote>
    <p>npm ERR! code ELIFECYCLE
    npm ERR! errno 1
    npm ERR! functions@ lint: <code>eslint .</code>
    npm ERR! Exit status 1
    npm ERR!
    npm ERR! Failed at the functions@ lint script.
    npm ERR! This is probably not a problem with npm. There is likely additional logging output above
    npm ERR! A complete log of this run can be found in:
    npm ERR!     C:\Users\PC\AppData\Roaming\npm-cache_logs\2018-11-09T12_26_46_311Z-debug.log
    Error: functions predeploy error: Command terminated with non-zero exit code1</p>
  </blockquote>