Mongoose v6 modifies connection options object

[BrettHoutz]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Mongoose version

6.12.6

Node.js version

20.10.0

MongoDB server version

6.0.4

Typescript version (if applicable)

No response

Description

mongoose.connect() sets the properties config, autoCreate, and autoIndex, which i understand to be mongoose-specific connection options. My application creates connections using both mongoose and mongodb and uses a common options object for both. When the options object is passed to mongodb.MongoClient.connect(), it has the properties that were added by mongoose, which causes an error from MongoClient.

Steps to Reproduce

const mongoose = require('mongoose');

const options = {
  connectTimeoutMS: 5000,
  socketTimeoutMS: 30000,
  readPreference: 'nearest',
};

mongoose.connect('mongodb://localhost:27017', options).then(() => {
  // config, autoCreate, and autoIndex are set in options
  console.log(options);
});

Expected Behavior

Since the options object is a set of static properties for configuring the behavior of Mongoose, i would expect that it not be modified at all.

[donoftime2018]

What I did was update mongoose to latest version 8.2.0. And it only shows the options listed in the options object.

#!/usr/bin/env node

const mongoose = require('mongoose');

const options = {
  connectTimeoutMS: 5000,
  socketTimeoutMS: 30000,
  readPreference: 'nearest'
};

mongoose.connect('mongodb://localhost:27017', options).then(() => {
  console.log(options); //latest version of mongoose only shows the options listed
});

[donoftime2018]

If you want to keep it at mongoose version 6.12.6, then removing readPreference only shows the fields listed in options.

#!/usr/bin/env node

const mongoose = require('mongoose');

const options = {
  connectTimeoutMS: 10,
  socketTimeoutMS: 10,
  autoCreate: false,
  autoIndex: true,
  config: {autoIndex: true},
//   readPreference: 'nearest'
};

mongoose.connect('mongodb://localhost:27017', options).then(() => {
  console.log(options); //only shows the options listed
});

[donoftime2018]

What I did was update mongoose to latest version 8.2.0. And it only shows the options listed in the options object.

#!/usr/bin/env node

const mongoose = require('mongoose');

const options = {
  connectTimeoutMS: 5000,
  socketTimeoutMS: 30000,
  readPreference: 'nearest'
};

mongoose.connect('mongodb://localhost:27017', options).then(() => {
  console.log(options); //latest version of mongoose only shows the options listed
});

I understand you wanted to not set other fields only on mongoose v6.

[vkarpov15]

This is a duplicate of #13335, fixed by cherry picking #13376.