Fix for carrierwave with imagevoodoo throwing JavaxImageIO IIOexception

Fix for carrierwave with imagevoodoo throwing JavaxImageIO IIOexception

# This module overrides mount_uploader method and assign methods
# in order to handle Java ImageIO exception which occurs for
# some png files and is unhandled by CarrierWave gem.
# If the file is invalid, it removes newly created
# files, assigns old file back and returns validation error.
module CarrierWavePngFix
  extend ActiveSupport::Concern

  module ClassMethods
    def mount_uploader(column, uploader=nil, options={}, &block)
      super

      class_eval <<-RUBY
        def #{column}=(new_file)
          old_val = #{column}.clone
          begin
            super
            @#{column}_upload_failed = false # reset invalid file flag
          rescue Java::JavaxImageio::IIOException
            @#{column}_upload_failed = true # set invalid file flag for validation
            super(old_val) # assign old value back
            #{column}_was.remove! # remove leftovers after invalid assignment
          end
        end

        validate :validate_#{column}_upload_failed

        def validate_#{column}_upload_failed
          errors.add(:#{column}, :corrupted_image) if @#{column}_upload_failed
        end
      RUBY
    end
  end
end