default_scope_crutch.rb

# This unfortunate hack is necessary because ActiveRecord doesn't provide any
# way (clean or otherwise) to circumvent the default_scope when preloading.
#
# Here's a closed-but-unresolved issue that goes into it a bit more:
#
#     https://github.com/rails/rails/issues/11036
#
# Example usage:
#
# In this scenario, Product and User may have paranoid deletes, and a
# default_scope of `where(deleted_at: nil)`, in which case the preloading
# queries may not find all associated records, and make your life a living
# hell.
#
# Wrapping the query in `disable_default_scopes` solves the problem by
# removing the default_scopes, running your block of code, and then
# restoring the default_scopes.
#
#     disable_default_scopes(Product, User) {
#       @orders = Order.preload(:product, :user).page(1).per(10)
#
#       # Note: One "gotcha" is that, depending on your context, you will likely
#       # need to force the actual loading of the data within the block.
#       @orders.load
#     }
#

module DefaultScopeCrutch

  def disable_default_scopes(*klasses)

    orig_scopes = {}

    klasses.each do |klass|
      klass.class_eval do
        orig_scopes[klass] = default_scopes
        self.default_scopes = []
      end
    end

    retval = yield

    klasses.each do |klass|
      klass.class_eval do
        self.default_scopes = orig_scopes[klass]
      end
    end

    retval

  end

end