"insertOne" callback gets called twice on error.

[neil-hardlight]

Do you want to request a feature or report a bug?
Bug

What is the current behavior?
"insertOne" callback gets called twice on error. Although I suspect the bug affects all collection APIs.

If the current behavior is a bug, please provide the steps to reproduce.
Call "insertOne" after disconnecting from the database to force an error. Notice that the callback gets called twice.

model.collection.insertOne(newModel, dbOptions, (err, result) => {
    if (err) {
        return next(err); <-- GETS CALLED TWICE
    }

I have isolated the issue to here:

drivers\node-mongodb-native\collection.js

Line 214:

} catch (error) {
    // Collection operation may throw because of max bson size, catch it here
    // See gh-3906
    if (typeof callback === 'function') {
        callback(error); <-- THIS SHOULD RETURN
    } else {
        this.conn.emit('operation-end', { _id: opId, modelName: _this.modelName, collectionName: this.name, method: i, error: error });
    }
    if (typeof lastArg === 'function') {
        lastArg(error); <-- THIS CALLS THE CB AGAIN
    } else {
        throw error;
    }
}

Higher up the file (line 162) you can see that the "callback" already calls "lastArg":

callback = function collectionOperationCallback(err, res) {
    if (err != null) {
        _this.conn.emit('operation-end', { _id: opId, modelName: _this.modelName, collectionName: _this.name, method: i, error: err });
    } else {
        _this.conn.emit('operation-end', { _id: opId, modelName: _this.modelName, collectionName: _this.name, method: i, result: res });
    }
    return lastArg.apply(this, arguments); <-- ALREADY CALLS LASTARG
};

What is the expected behavior?
Callback only gets called once.

What are the versions of Node.js, Mongoose and MongoDB you are using? Note that "latest" is not a version.
Mongoose 6.0.12
Node 14.17.0

[IslandRhythms]

ReferenceError: next is not defined

[neil-hardlight]

model.collection.insertOne(newModel, dbOptions, (err, result) => {
    if (err) {
        return next(err); <-- GETS CALLED TWICE
    }

This is not a complete code sample - it's a fragment. I'm just showing that on-error, the callback from "insertOne" is called twice. I can simplify it to:

model.collection.insertOne(newModel, dbOptions, (err, result) => {
    if (err) {
        console.log('This log message will be displayed twice');
    }

Does that help with clarifying the problem?

[IslandRhythms]

const mongoose = require('mongoose');

const testSchema = new mongoose.Schema({
    name: String
});

const Test = mongoose.model('Test', testSchema);
const OtherModel = mongoose.model('OtherModel', testSchema);

async function test() {
    await mongoose.connect('mongodb://localhost:27017/', {useNewUrlParser: true,
    useUnifiedTopology: true,});
    await mongoose.connection.dropDatabase();
    await Test.create({ name: 'Daniel '});
    mongoose.connection.close();
    mongoose.connection.on('disconnected', () => {
        Test.collection.insertOne(OtherModel, {}, (err, result) => {
            if(err) return console.log('should show twice');
        });
    });
}

mongoose.connection.on('open', () => {
    console.log('open fire');
});

mongoose.connection.on('connected', () => {
    console.log('connected successfully');
});

test();

[neil-hardlight]

Thank you for your code sample - as you can see, it behaves as I described:

connected successfully
open fire
should show twice
should show twice