[mongoid] validates_uniqueness_of not working for embedded / inherited documents?

[kshet26]

Let's say I have a User model with a field of :username. If a person
signs up with an already used :username,
validates_uniqueness_of :username fails correctly and prevents the
record from being saved.

Now let's say I have a Friendship model (with a field
of :target_user_id) that is inherited from a Relationship model.
Friendships get embedded into User.

If a person tries to create multiple Friendships with the
same :target_user_id value, validates_uniqueness_of :target_user_id
DOES NOT fail. As a sanity check, I checked if
validates_length_of :target_user_id, :maximum => 2 would fail and it
does correctly.

Is this a bug or am I missing something in the way that Mongoid works?

[kshet26]

Anyone have any information on this? Is this intended or a possible
bug?

[Durran Jordan]

Probably need a little more thought around this, but right now it
would not work... I guess the best would be for mongoid's validator to
be smart enough to check if the field was unique for the same embedded
types across the database, or if a scope option was supplied then it
could be scoped to potentially just it's parent... I've seen some
forks already working on this type of solution.

[kshet26]

Would a validation be more efficient than me doing a query to see if a
matching record already exists?

[Durran Jordan]

You can do the query now as a workaround in a custom validator... The
validation once it would not be much different as far as efficiency
goes.

[kshet26]

That's what I thought, thanks so much!

[tadatoshi]

I've just found that validation on presence (I use
"validates :locale, :presence => true" like ActiveModel in Rails 3.0)
also doesn't fail on embedded document.
Strange thing is that it puts an error message correctly but the
document is still saved.