doc.set({ field: undefined }) does nothing if the schema has strict: false

[lantw44]

Prerequisites

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

Mongoose version

7.8.6

Node.js version

22.11.0

MongoDB server version

8.0.4

Typescript version (if applicable)

5.7.3

Description

If the schema has strict: false, you can't use doc.set({ field: undefined }) to unset a field. Instead, you have to use doc.set('field', undefined) or doc.field = undefined.

Steps to Reproduce

import mongoose from 'mongoose';

mongoose.connect('mongodb://localhost/test2');

const helloSchema = new mongoose.Schema({
  name: { type: String, required: true },
  status: { type: Boolean, required: true },
  optional: { type: Number },
}, { strict: false });
const Hello = mongoose.model('Hello', helloSchema);

const obj = new Hello({ name: 'abc', status: true, optional: 1 });
const doc = await obj.save();

doc.set({ optional: undefined });

console.log('doc.isModified()', doc.isModified());
console.log('doc.optional', doc.optional);

await doc.save();

process.exit();

doc.isModified() false
doc.optional 1

Expected Behavior

doc.isModified() true
doc.optional undefined