instance_scope_proc.rb

class CodefileGenerator < Jekyll::Generator

    NON_CODE_EXTENSIONS = [
        'html',
        'md'
    ]

    is_dotfile = proc { |f| ['.', '..'].include? f }
    f_ext = proc { |f| f.slice /\.(.*)$/, 1 }
    is_non_codefile = proc { |f| non_code_extensions.include? f_ext[f] }

    def generate(site)
        site.pages.each do |page|
            dir = File.dirname(page.path)
            if !File.exists? dir
                # for generated pages (like week schedules)
                next
            end
            codefiles = Dir.entries(dir)
                .reject(&is_dotfile)
                .reject(&is_non_codefile)
            page.data['codefiles'] = codefiles
        end
    end

end