Metanorma script that fixes Lucid / LucidChart SVG files that have `<use>` elements reference invalid IDs, see https://community.lucid.co/lucid-for-engineering-19/svg-export-results-in-invalid-idref-on-a-use-element-8050

metanorma-fix-lucid-svgs.rb

#!/usr/bin/env ruby

# This script is developed for Metanorma users that need to fix Lucid-generated
# SVGs. Lucid-generated SVGs have `<use>` elements reference invalid IDs, which
# result in invalid SVG XML. Metanorma PDFs and Word outputs rely on valid SVG
# XML files otherwise the PDF output will omit broken SVGs, and the Word output
# will have EMF files that have areas of the figures appear in black.
#
# The issue is described at:
# https://community.lucid.co/lucid-for-engineering-19/svg-export-results-in-invalid-idref-on-a-use-element-8050
#
# As of 2025-06-26, this issue is not fixed.

require 'thor'
require 'nokogiri'
require 'fileutils'
require 'set'

class SvgLucidFix < Thor
  # Fix Thor deprecation warning
  def self.exit_on_failure?
    true
  end

  # Make fix the default command
  default_command :fix
  desc "fix PATH", "Fix SVG files by removing use elements with invalid IDREF"
  method_option :inplace, type: :boolean, default: false, aliases: "-i",
                desc: "Modify files in place"
  method_option :output, type: :string, aliases: "-o",
                desc: "Output directory for modified files (required if not using --inplace)"

  def fix(path_pattern)
    files = Dir.glob(path_pattern)

    if files.empty?
      puts "No files found matching pattern: #{path_pattern}"
      exit 1
    end

    unless options[:inplace] || options[:output]
      puts "Error: Either --inplace or --output must be specified"
      exit 1
    end

    if options[:output] && !options[:inplace]
      unless Dir.exist?(options[:output])
        begin
          FileUtils.mkdir_p(options[:output])
          puts "Created output directory: #{options[:output]}"
        rescue => e
          puts "Error creating output directory: #{e.message}"
          exit 1
        end
      end
    end

    files.each do |file|
      process_svg_file(file)
    end
  end

  private

  def process_svg_file(file)
    begin
      # Parse the SVG file
      doc = File.open(file) { |f| Nokogiri::XML(f) }

      # Find all elements with ID attributes
      existing_ids = Set.new
      doc.xpath('//*[@id]').each do |element|
        existing_ids.add(element['id'])
      end

      # Find all use elements with xlink:href attributes
      invalid_use_elements = []
      doc.xpath('//svg:use', 'svg' => 'http://www.w3.org/2000/svg').each do |use_element|
        href = use_element['xlink:href'] || use_element['href']
        next unless href

        # Extract the ID from the href (removing the # prefix)
        id_ref = href.sub(/^#/, '')

        # Check if the ID exists in the document
        unless existing_ids.include?(id_ref)
          invalid_use_elements << use_element
        end
      end

      # Remove invalid use elements
      if invalid_use_elements.any?
        invalid_use_elements.each(&:remove)
        puts "Fixed #{file}: Removed #{invalid_use_elements.size} invalid use elements"

        # Save the modified SVG
        if options[:inplace]
          output_path = file
        else
          output_path = File.join(options[:output], File.basename(file))
        end

        File.write(output_path, doc.to_xml)
      else
        puts "No invalid use elements found in #{file}"
      end
    rescue => e
      puts "Error processing #{file}: #{e.message}"
    end
  end
end

# Allow the script to be run with bundle exec
if $0 == __FILE__
  SvgLucidFix.start(ARGV)
end