Wangjohn validates associated uniqueness

[wangjohn]

Pull request in response to #4568. Uses jeyb's pull request and cleans up some code.

[tenderlove]

Can you check to see if the strip is actually necessary?

[wangjohn]

Ok, I'm now using grep and have fixed the indent.

[schneems]

You could clean up the protected method unique_for_nested_attributes? by pulling out some of the logic into other methods something like this:

def unique_for_nested_attributes?(collection)
  return true if collection.empty?
  uniq_validators = uniq_validators_for(collection)
  return true if uniq_validators.empty?

  validations = nested_validations(collection, uniq_validators)

  collection.length == validations.length
end

def uniq_validators_for(collection)
  validator = ActiveRecord::Validations::UniquenessValidator
  collection.first.class.validators.grep(validator)
end

def uniq_attributes_for(validators)
  validators.flat_map do |validator|
    [validator.attributes, validator.options[:scope]]
  end.compact.to_set
end

def distinct_validations_on_attributes(collection, attributes)
  collection.map do |record|
    record.attributes.select { |k,v| attributes.include?(k.to_sym) }.values.join("")
  end.uniq
end

def nested_validations(collection, validations)
  attributes = uniq_attributes_for(validators)
  distinct_validations_on_attributes(collection, attributes)
end

Though this is just an off-the cuff refactoring, you'll want to pick some better names for methods, and make sure none of the logic was lost in the translations (just run the tests). I also changed Set.new to call .to_set on the array, and changed the multi line block syntax from { to do/end and moved from map.flatten to a flat_map. Even after refactoring this, i'm not 100% sure how this logic works, commenting on individual methods could help.

Thanks a ton for submitting this, the more people with more knowledge of Active Record code, the better ❤️

[wangjohn]

Actually, I realized the code I wrote will have a bug. Consider the following test case:

  def test_validates_associated_nested_attributes_uniequeness_with_scoping
    Topic.validates_associated(:replies)
    Topic.accepts_nested_attributes_for(:replies)
    Reply.validates_uniqueness_of(:title, :scope => :content)

    t = Topic.create("title" => "Programming", "content" => "For the masses")
    t.replies_attributes = [{"title" => "aa", "content" => "aa"}, {"title" => "a", :content => "aaa"}]

    assert t.valid?
    t.save!
    assert_equal 2, t.replies.size
  end

Because of the way I'm joining the values together, this test will fail. I'm going to close this PR and make a new one when I've got time to work on this more.