3.x no longer properly checks multiple scope in uniqueness

[weppos]

We have the following code in a model

  validates :label, uniqueness: { scope: :account_id, message: "already exists for this account", allow_nil: true }
  validates :label, uniqueness: { scope: :user_id, message: "already exists for this user", allow_nil: true }

And the following spec

  describe "validations" do
    subject { FactoryGirl.build(:access_token) }

    it { FactoryGirl.create(:user_access_token, label: "Existing")
         is_expected.to validate_uniqueness_of(:label).scoped_to(:user_id).with_message("already exists for this user").allow_nil }

    it { FactoryGirl.create(:account_access_token, label: "Existing")
         is_expected.to validate_uniqueness_of(:label).scoped_to(:account_id).with_message("already exists for this account").allow_nil }
  end

With 2.x the spec was passing. With 3.x the spec is no longer passing with this error

     Failure/Error: is_expected.to validate_uniqueness_of(:label).scoped_to(:user_id).with_message("already exists for this user").allow_nil }
       Expected validation to be scoped to [:user_id], but it was scoped to [:account_id].

It looks like 3.x doesn't properly understand multiple uniqueness with different scopes on the same attribute.

[mcmire]

Yes, this is a known issue with 3.0. It was already filed as #830, so I'll keep the discussion there.