mongoose updateOne add pre then no return

[tingfeima]

Prerequisites

• I have written a descriptive issue title

Mongoose version

6.5.1

Node.js version

v14.17.3

MongoDB version

4.2

Operating system

macOS

Operating system version (i.e. 20.04, 11.3, 10)

12.4

Issue

  schema.pre('updateOne'，async function (doc, next) {
    const updateInfo = {}
    // do stuff...
    this._update.$set = { ...updateInfo }
    return next()
  })

  const result = await model.updateOne(
    {
     nickname:'mark',
    },
    { $set: { updatedAt:new Date() } }
  )
  console.log(result)  // undefined

why the result is undefined

[eternalbasic1]

I guess, As you are using await and async and javascript is a Single-Threaded & Synchronous Language it just execute the code line by line very fast. As you are using async and await which internally deals with Event loop/ TaskQueue/MicroTask. Just waiting for call stack to empty. Why don't you make a the console.log inside a settimeout function and see it, I feel it works when you use a
settimeout(console.log(result),2000);
at the last line

[vkarpov15]

The following prints undefined. But prints an update result object if you remove the next() call. Strange.

'use strict';

const mongoose = require('mongoose');
mongoose.set('debug', true);

const schema = mongoose.Schema({ name: String });
schema.pre('updateOne', async function(doc, next) {
  this._update = this._update || {};
  this._update.$set = { name: 'foo' };
  //return next();
  next();
});
const Test = mongoose.model('Test', schema);

run().catch(err => console.log(err));

async function run() {
  await mongoose.connect('mongodb://localhost:27017/mongoose_test');
  const res = await Test.updateOne();
  console.log(res);
  process.exit(0);
}

[vkarpov15]

The issue is that next is the first parameter to pre hooks, not the second. Do the following instead and it will work fine:

schema.pre('updateOne'，async function (next) { // <-- remove `doc` as first parameter here
  const updateInfo = {}
  // do stuff...
  this._update.$set = { ...updateInfo }
  return next()
})

The issue is that Mongoose calls the updateOne hook with next as the first argument, and the final callback that it should call once all hooks are done as the 2nd argument. Admittedly this is not a great design choice, and mongoosejs/kareem#36 fixes that. But, in the meantime, please fix your argument order and this will work fine.