Each then() should return a value or throw promise/always-return

Question

I am creating a push notification app, I use node.js for deploying firebase function but when deploying this shows error.

warning Avoid nesting promises promise/no-nesting

warning Avoid nesting promises promise/no-nesting

error Each then() should return or throw promise/always-return

This is my Code :

"use-strict";

const functions = require("firebase-functions");
const admin = require("firebase-admin");
admin.initializeApp(functions.config().firebase);

exports.sendNotification = functions.firestore
  .document("Users/{user_id}/Notification/{notification_id}")
  .onWrite(event => {
    const user_id = event.params.user_id;
    const notification_id = event.params.notification_id;

    return admin
      .firestore()
      .collection("Users")
      .doc(user_id)
      .collection("Notification")
      .doc(notification_id)
      .get()
      .then(queryResult => {
        const from_user_id = queryResult.data().from;
        const from_message = queryResult.data().message;
        const from_data = admin
          .firestore()
          .collection("Users")
          .doc(from_user_id)
          .get();
        const to_data = admin
          .firestore()
          .collection("Users")
          .doc(user_id)
          .get();

        return Promise.all([from_data, to_data]).then(result => {
          const from_name = result[0].data().name;
          const to_name = result[1].data().name;
          const token_id = result[1].data().token_id;
          const payload = {
            notification: {
              title: "Notification From :" + from_name,
              body: from_message,
              icon: "default"
            }
          };

          return admin
            .messaging()
            .sendToDevice(token_id, payload)
            .then(result => {
              console.log("Notification Sent.");
            });
        });
      });
  });

The formatting and indenting of your function here makes it difficult to read. — Doug Stevenson, Apr 02 '18 at 05:47

score 4 · Accepted Answer · answered Apr 02 '18 at 04:10

You have not mentioned where the error is. I think the error would be at line

console.log("Notification Sent.");

If you do

return console.log("Notification Sent.");

the error should go away while the warnings would still persist.

As Marcos mentioned above, its better to chain the promises and not do nesting.

Each then() should return a value or throw promise/always-return

1 Answers1