webpack_filter.rb

class WebpackFilter < Nanoc::Filter
  require 'tempfile'
  require 'fileutils'

  identifier :webpack
  type :text

  def run(text, options = {})
    tmp_file = Tempfile.new('webpack', item_dir)
    ##
    # Run webpack.
    run_webpack File.join(content_dir, item.path), output_dir

    ##
    # Copy WebAssembly files into place.
    Dir[File.join(item_dir, "*.wasm")].each do |wasm_file|
      FileUtils.mkdir_p(output_dir)
      FileUtils.mv(wasm_file, output_dir)
    end

    ##
    # Read transpiled contents, and pass it back to nanoc.
    File.read File.join(content_dir, item.path)
  ensure
    tmp_file.unlink
    tmp_file.close
  end

  private

  def run_webpack(src, dest)
    system "webpack", "--entry", "./#{src}", "--output-path", dest
    raise unless $?.success?
  end

  def output_dir
    File.join config.output_dir, File.dirname(item.path)
  end

  def content_dir
    source = config[:data_sources].find { _1[:type] == "filesystem" }
    source[:content_dir]
  end

  def item_dir
    File.join(content_dir, File.dirname(item.path))
  end
end