span_style_transformer.rb

    span_trans = lambda do |el|
      if el[:node].name == "span"
        if el[:node].has_attribute?("style")
          rules = el[:node].attribute("style").value.split(";")
          new_rules = rules.map do |rule|
            rule.match(/text-decoration:\s*(underline|overline|line-through)\b/) ||
            rule.match(/font-weight:\s*bold\b/) ||
            rule.match(/font-style:\s*italic\b/)
          end
          new_style = new_rules.compact.map{|r| r.to_s}.join("; ")
        end
      
        if new_style == "" || !el[:node].has_attribute?("style")
          el[:node].children.each { |n| el[:node].add_previous_sibling(n) }
          el[:node].unlink
        end
      end

      {:node => el[:node]}
    end

Curious, how did you test this? I'm trying to adapt this to whitelist all style attributes, plus text-align values, but it's not working calling through Sanitize.

Also, I'm not seeing where the new_style is being added back to the node, am I missing something?