model.validate is dropped if the same validator-method is used twice

When having multiple calls to validate (with different conditions) only one is used.

  class Topic
    include ActiveModel::Validations
    include ActiveModel::Validations::Callbacks

    Topic.validate :forbid_swearing, :on => :create
    Topic.validate :forbid_swearing, :on => :update, :unless => :approved

    def forbid_swearing
      # ...
    end
  end

validate_quota won't be called on creation (Post.new.valid?(:create)).

The following test can be added to the #activemodel@ test set, to demonstrate that behavior:

  def test_multiple_validators_with_same_name
    Topic.class_eval do
      def forbid_swearing
        if title and title.include?("bad")
          errors.add("title", "must not contain swearing")
        end
      end
    end
    
    Topic.validate :forbid_swearing, :on => :create
    Topic.validate :forbid_swearing, :on => :update, :unless => :approved
    
    t = Topic.new(:title => "bad")
    assert t.invalid?(:create)
    assert t.invalid?(:update)
    
    t.approved = true
    assert t.invalid?(:create)
    assert t.valid?(:update)
  end

Now there are workarounds for this issue. Since the validators heavily rely on ActiveSupports callback implementation I don't think it makes much sense to it.

But a clear warning or exception would have made my debug-session a lot easier.