Unique index constraint does not work on indexes that are using array matching

[Wizzerinus]

So, MongoDB allows using indexes on lists like this:

collection.create_index("mike.first", unique=1)
collection.insert_one({"mike": [{"first": "value"}]})
collection.insert_one({"mike": [{"first": "value"}]})

Link to documentation

This will not work in MongoDB because both items include a list item with mike.[index].first == value. However, this is valid in Mongomock and causes my tests to fail.

My usecase: I have a login system that allows a user to have multiple login methods and am using an index of type [("login_methods.identifier", 1), ("login_methods.login_type", 1)] to prevent multiple users from having the same login method (while login_methods is a list).