错误“函数返回未定义的、预期的promise或值”，即使在所有地方返回后也是如此

Question

我是Node.js的新手，即使在阅读了其他stackflow用户提供的教程之后，我也在为承诺而挣扎。我已经花了整整一个晚上在这方面，我正在寻求帮助。我得到以下错误“Function return undefined,expected Promise or value”。我的代码在下面。我做错了什么？我还怀疑我必须使用await/async，因为它看起来像是我的代码在没有等待第一个get完成的情况下运行。

const admin = require('firebase-admin');
const functions = require('firebase-functions');
var db = admin.firestore();

exports.declinedRequest = functions.firestore
.document('requests/{requestId}')
.onUpdate((change, context) => {
  const newValue = change.after.data();
  const status = newValue.status;
  const request = context.params.requestId;
  var registrationToken;
  var message;

  if(status=="created") {
    console.log('Checkpoint1 ',context.params.requestId);
    newValue.friends.forEach(doc => {
      console.log('Checkpoint 2: ', doc);

      var usersRef = db.collection('users');
      var query = usersRef.where('mobile', '==', doc).get()
        .then(snapshotFriend => {
          if (snapshotFriend.empty) {
            console.log('Checkpoint3.');
            return;
          }  

        snapshotFriend.forEach(mobile => {

        registrationToken = mobile.data().fcmToken;
        console.log('FCM token =>', registrationToken);
        if (!registrationToken) {
          console.log('No fcmToken available');
          return;
        }  
         message = {
          notification: {
            body: "Request still available from " + newValue.requesterName,
            sound: "default", 
            badge: 1
            },
          data: {
            requestId: `${request}`
          }
        };

        console.log('FCM token message created');

        }) 
      })
    })
  } else {
    return;
  }
 return admin.messaging().sendToDevice(registrationToken, message)
      .then(function (response) {
        console.log("Successfully sent message:", response)
     })
      .catch(function (error) {
        console.log("Error sending message:", error);
     }) 

})

Answer 1

尝试下面的代码，希望这将工作。

    const admin = require('firebase-admin');
    const functions = require('firebase-functions');
    const Promise = require('bluebird');
    const _ = require('lodash');
    let db = admin.firestore();

    exports.declinedRequest = functions.firestore
    .document('requests/{requestId}')
    .onUpdate((change, context) => {
        const newValue = change.after.data();
        const status = newValue.status;
        const request = context.params.requestId;
        if (status == "created") {
            console.log('Checkpoint1 ', context.params.requestId);
            allPromises = [];
            newValue.friends.forEach(doc => {
                console.log('Checkpoint 2: ', doc);
                const usersRef = db.collection('users');
                // query for each document return promise.
                allPromises.push(queryForEachDocument(doc,request,usersRef));
            });
            return Promise.all(allPromises);
        } else {
            return Promise.reject / resolve('Whatever you want.');
        }
    })

    function queryForEachDocument(doc,request,usersRef) {
    let promiseInvoices = []
    let registrationToken;
    let message;
    return usersRef.where('mobile', '==', doc).get().then((snapshotFriend) => {
        if (_.isEmpty(snapshotFriend)) {
            console.log('Checkpoint3.');
            return Promise.reject(new Error('Your error'));
        }
        snapshotFriend.forEach(mobile => {
            registrationToken = mobile.data().fcmToken;
            console.log('FCM token =>', registrationToken);
            if (!registrationToken) {
                console.log('No fcmToken available for', newValue.requesterName);
                // Do anything you want to change here.
                return Promise.reject(new Error('No fcmToken available for',newValue.requesterName));
            }
            message = {
                notification: {
                    body: "Request still available from " + newValue.requesterName,
                    sound: "default",
                    badge: 1
                },
                data: {
                    requestId: request
                }
            };
            console.log('FCM token message created');
            // send invoice for each registrationToken
            promiseInvoices.push(sendInvoice(registrationToken, message))
        });
    }).then(() => {
        return Promise.all(promiseInvoices);
    })
    }
    function sendInvoice(registrationToken, message) {
    return admin.messaging().sendToDevice(registrationToken, message)
        .then(function (response) {
            console.log("Successfully sent message:", response)
        })
        .catch(function (error) {
            console.log("Error sending message:", error);
        })
    }