fix(document): throw error if overwriting array selected with $slice

[vkarpov15]

Fix #2432

Summary

Currently, if you use a $elemMatch projection and try to save, Mongoose will throw a DivergentArrayError:

const user = await User.create({
    sessions: [{ token: 'one' }, { token: 'two' }]
  });

  const doc = await User.findById(user._id).select({
    sessions: { $elemMatch: { token: 'two' } }
  });

  doc.sessions.push({ token: 'three' });

  // Throws "For your own good, using `document.save()` to update an array which was selected using an $elemMatch or $slice projection OR populated using skip, limit, query conditions, or exclusion of the _id field when the operation results in a $pop or $set of the entire array is not supported. The following path(s) would have been modified unsafely:
  sessions"
  await doc.save().then(() => null, err => err);

The crux of #2432 is we should do that for $slice as well. But only for $set atomics - if save() would just $push or $pull or $pop from the array then that won't overwrite the existing array.

Examples

[Copilot]

Pull request overview

Extends divergent-array detection so document.save() throws DivergentArrayError when an array selected via a $slice projection would be overwritten via a $set atomic, while allowing safe $push/$pull/$pop/$addToSet updates. Fixes #2432.

Changes:

• checkDivergentArray() now also flags arrays selected with $slice when modifications resolve to a $set atomic.
• DivergentArrayError message updated to mention $slice.
• Adds tests covering $set, $push, $pull, $pop, $addToSet behavior on $slice-selected arrays.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated no comments.

File	Description
lib/document.js	Adds $slice projection check in checkDivergentArray() returning the top path when atomics contain $set.
lib/error/divergentArray.js	Updates error message to mention $slice projection.
test/model.field.selection.test.js	Adds tests verifying divergent error for $set and successful saves for $push/$pull/$pop/$addToSet.