default_value_for on a non-column attribute doesn't honor initialized attributes when allows_nil is false.

[erichmenge]

Here's what's currently in default_value_for.rb

        attribute_blank = if column && column.type == :boolean
          attributes[attribute].nil?
        else
          attributes[attribute].blank?
        end

Since the attributes hash is the only thing inspected, for non-column values this will always be nil.

It seems like the fix for this should be as easy as switching from checking the attributes hash to using the getter method.

[erichmenge]

The test_also_works_on_attributes_that_arent_database_columns test currently passes by accident because of:

        # allow explicitly setting nil through allow nil option
        next if @initialization_attributes.is_a?(Hash) &&
                (
                  @initialization_attributes.has_key?(attribute) ||
                  (
                    @initialization_attributes.has_key?("#{attribute}_attributes") &&
                    nested_attributes_options.stringify_keys[attribute]
                  )
                ) &&
                !self.class._all_default_attribute_values_not_allowing_nil.include?(attribute)

Since it is nil, and allows_nil is the default, it doesn't update the value.