Firebase Cloud Messaging生成错误

Question

I am trying to trigger a push notification whenever a document field is written to. Since I am brand new to node.js I am having difficulty debugging this seemly easy function. Here is my code:

// The Cloud Functions for Firebase SDK to create Cloud Functions and setup triggers.
const functions = require('firebase-functions');

// The Firebase Admin SDK to access the Firebase Realtime Database.
const admin = require('firebase-admin');
admin.initializeApp(functions.config().firebase);

exports.sendNotification = functions.firestore.document("Customer_Data/{userEmail}/Placed_Orders/{orderId}/status").onWrite(event => {
  const userEmail = event.params.userEmail;

  const message = "Your meal will be delivered in 2 hours";
  const title = "Eat Away";

  const toUser = admin.firestore().collection("Customer_Data").doc(userEmail).get();

  return admin.firestore().collection("Customer_Data").doc({userEmail}).get().then(queryResult => {
    const tokenId = queryResult.data().tokenId;

    const notificationContent = {
      notification: {
        title: title,
        body: message,
      }
    }
  });

  return admin.messaging().sendToDevice(tokenId , notificationContent).then(function(response) {
    console.log("Message sent successfully");
  }).catch(function(error){
    console.log("Error sending message:", error);
  });

});

And here is the error I receive in the terminal:

 53:11  warning  Avoid nesting promises                      promise/no-nesting
  53:11  warning  Avoid nesting promises                      promise/no-nesting
  53:77  warning  Unexpected function expression              prefer-arrow-callback
  53:77  error    Each then() should return a value or throw  promise/always-return
  55:13  warning  Unexpected function expression              prefer-arrow-callback

✖ 5 problems (1 error, 4 warnings)
  0 errors and 2 warnings potentially fixable with the `--fix` option.

npm ERR! code ELIFECYCLE
npm ERR! errno 1
npm ERR! functions@ lint: `eslint .`
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.

Error: functions predeploy error: Command terminated with non-zero exit code1

I did not use a promise because I didn't see the point of it. But at the same time I tried it out and it did not help.

Answer 1

Not seeing the point of promises is typically a reason to learn more about them, not to not use them.

The way you've now written your code means that a part of it never runs. This doesn't have anything to do with promises yet, but simply with the fact you have two return statements in the main flow of your code:

exports.sendNotification = functions.firestore.document("Customer_Data/{userEmail}/Placed_Orders/{orderId}/status").onWrite(event => {
  ...
  return admin.firestore().collection("Customer_Data").doc({userEmail}).get().then(queryResult => {
    ...
  });

  // Nothing below this line ever executes
  return admin.messaging().sendToDevice(tokenId , notificationContent).then(function(response) {
    console.log("Message sent successfully");
  }).catch(function(error){
    console.log("Error sending message:", error);
  });
});

In this case you need the results from Firestore to send the FCM message, which means you need to wait for the Firestore promise to resolve (with then() or await ) before calling FCM:

exports.sendNotification = functions.firestore.document("Customer_Data/{userEmail}/Placed_Orders/{orderId}/status").onWrite(event => {
  const userEmail = event.params.userEmail;

  const message = "Your meal will be delivered in 2 hours";
  const title = "Eat Away";

  const toUser = admin.firestore().collection("Customer_Data").doc(userEmail).get();

  return admin.firestore().collection("Customer_Data").doc({userEmail}).get().then(queryResult => {
    const tokenId = queryResult.data().tokenId;

    notificationContent = {
      notification: {
        title: title,
        body: message,
      }
    }

    return admin.messaging().sendToDevice(tokenId , notificationContent);
  })
});