Warn when using skip without sort

[199911]

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

What is the current behavior?
Populate with options, skip does not work when sort not defined
.populate({ options: {skip, limit} })

If the current behavior is a bug, please provide the steps to reproduce.
https://github.com/199911/mongoose-populate-bug/blob/master/index.js#L98

What is the expected behavior?
Story list have stories [A, B, C]
expect .populate({ options: {skip: 0, limit: 1} }) return A
expect .populate({ options: {skip: 1, limit: 1} }) return B
but .populate({ options: {skip: 1, limit: 1} }) still return A

Please mention your node.js, mongoose and MongoDB version.
Node,js 8, mongoose 5, MongoDB 4

[vkarpov15]

I took a closer look at this and you need to specify sort here, because MongoDB doesn't guarantee order of query results unless you specify sort, so skip without sort doesn't really make sense. Mongoose does send the correct query and handle the result correctly, it's just that the MongoDB server is returning an incorrect doc unless you explicitly sort.

    before('Get first story', async () => {
      const list = await StoryList
        .findById('333333333333333333333333')
        .populate({
          path: 'stories',
          options: {
            skip: 1,
            limit: 1,
            sort: { $natural: -1 }
          },
        }); 
      story = list.stories[0];
    });

[199911]

@vkarpov15
Understand this is not a flaw in Mongoose.
Can find some way to notify Mongoose users?

Maybe jotting down this problem in the API documents
or throw an error when calling populate() with skip but without sort?

[vkarpov15]

Worth considering for a future release