How to check modified state on nested schemas

[jsardev]

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

A bug, I guess.

What is the current behavior?

doc.modifiedPaths() returns that paths have been modified (even if they didn't) on models that have nested schemas. What is also interesting: it works completely fine when i don't do type: ChildSchema and just embed the schema inline.

If the current behavior is a bug, please provide the steps to reproduce.

const BarSchema = new Schema(
  {
    bar: {
      type: String
    }
  },
  { _id: false }
);

const FooNestedSchema = new Schema({
  foo: {
    type: BarSchema
  }
});

const FooSchema = new Schema({
  foo: {
    bar: {
      type: String
    }
  }
});

const FooNested = mongoose.model('fooNested', FooNestedSchema);
const fooNested = new FooNested({ foo: { bar: 'value' } });

const Foo = mongoose.model('foo', FooSchema);
const foo = new Foo({ foo: { bar: 'value' } });

(async () => {
  await fooNested.save();
  await foo.save();

  fooNested.set({ foo: { bar: 'value' } });
  foo.set({ foo: { bar: 'value' } });

  fooNested.modifiedPaths(); // WRONG: [ 'foo', 'foo.bar' ]
  foo.modifiedPaths(); // CORRECT: []
})();

What is the expected behavior?

It would be a lot less confusing if both examples would behave the same.

Please mention your node.js, mongoose and MongoDB version.

• Node.js: 10.9.0
• Mongoose: 5.2.17

Additional info

Is there any workaround for this issue? Can I somehow manually check for equality on a saved document? schema.pre('validate', () => {}) gives me only access to the already changed document, which is already a bummer. Any ideas?

[vkarpov15]

Thanks for reporting, will look into this ASAP. As a workaround, you can use a deep equality check like lodash.deepEquals(), just make sure you call toObject() on both documents that you're comparing.