Arrays on nested object are emptied on save if an other object of the same parent object is in projection

[Getz85]

Prerequisites

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

Mongoose version

6.9.2

Node.js version

18.12.1

MongoDB server version

4.2.23

Typescript version (if applicable)

No response

Description

If a projection is made on a nested object on find, the arrays defined in the parent object are emptied on save.

Steps to Reproduce

const mongoose = require("mongoose");
(async () => {
    try {
        await mongoose.connect("mongodb://127.0.0.1:27017/test");
        // Define a schema wich contains an object (obj) composed of an object (subObj) and an array (subArr)
        const testSchema = new mongoose.Schema({
            str: 'string',
            obj: {
                subObj: {
                    str: 'string'
                },
                subArr: [{
                    str: 'string'
                }]
            },
            arr: [{
                str: 'string'
            }]
        });
        const Test = mongoose.model('Test', testSchema);
        // Create one test document : obj.subArr[0].str === 'subArr.test1'
        await Test.create({
            str: 'test1',
            obj: {
                subObj: {
                    str: 'subObj.test1'
                },
                subArr: [{
                    str: 'subArr.test1'
                }]
            },
            arr: [{str: 'arr.test1'}]
        });
        // Find the document with a obj.subObj projection
        const tests = await Test.find({str: 'test1'}, "str obj.subObj");

        for (const test of tests) {
            // Update one property
            test.str = test.str + ' - updated';
            await test.save();
            // obj.subArr is empty in database
        }
        process.exit(0);
    } catch (err) {
        console.error(err);
        process.exit(1);
    }
})();

Expected Behavior

The arrays not projected must not be emptied on save

[IslandRhythms]

const mongoose = require("mongoose");
(async () => {
    try {
        await mongoose.connect("mongodb://127.0.0.1:27017/test");
        await mongoose.connection.dropDatabase();
        // Define a schema wich contains an object (obj) composed of an object (subObj) and an array (subArr)
        const testSchema = new mongoose.Schema({
            str: 'string',
            obj: {
                subObj: {
                    str: 'string'
                },
                subArr: [{
                    str: 'string'
                }]
            },
            arr: [{
                str: 'string'
            }]
        });
        const Test = mongoose.model('Test', testSchema);
        // Create one test document : obj.subArr[0].str === 'subArr.test1'
        await Test.create({
            str: 'test1',
            obj: {
                subObj: {
                    str: 'subObj.test1'
                },
                subArr: [{
                    str: 'subArr.test1'
                }]
            },
            arr: [{str: 'arr.test1'}]
        });
        // Find the document with a obj.subObj projection
        const tests = await Test.find({str: 'test1'}, "str obj.subObj");

        for (const test of tests) {
            // Update one property
            test.str = test.str + ' - updated';
            await test.save();
            // obj.subArr is empty in database
        }
        console.log(await Test.find())
        process.exit(0);
    } catch (err) {
        console.error(err);
        process.exit(1);
    }
})();

[vkarpov15]

Confirmed that this bug is fixed by #13135