M1 Mac futzing about with EDID and name of display

edid_rename_display.rb

#!/usr/bin/ruby
# Create display override file to force Mac OS X to use a different name for the display
# This doesn't quite work since it just appends the alphanumeric serial number of whichever display of any given type to all of the names of the that type of display.
require 'base64'
edit_bytes = false
data=`ioreg -l -w0 -d0 -r -c AppleCLCD2`
# edid_hex=data.match(/EDID UUID.*?<([a-z0-9]+)>/i)
edid_hexes = data.scan /(?<="EDID UUID" = ).+/
# pp edid_hex; puts
display_attributes = data.scan /(?<="DisplayAttributes" = ).+/
# pp display_attributes; puts

edid_hexes.each_with_index do |edid, i|
  puts "EDID UUID #{edid}"
  dai = display_attributes[i].gsub('=', ' => ')
  # puts dai;puts '*************'
  dai = dai.gsub(/=> ([^"({].*?)(?=[,}])/, '=> "' + '\1' + '"').gsub(/","/, '", "')
  # puts dai
  display_attributes_hash = eval(dai)
  product_attributes = display_attributes_hash["ProductAttributes"]
  pp product_attributes
  vendorid = product_attributes["LegacyManufacturerID"]
  vendorid_hex = vendorid.to_i.to_s(16)
  # puts vendorid_hex
  productid = product_attributes["ProductID"]
  productid_hex = productid.to_i.to_s(16)
  # puts productid_hex
  alphanumeric = product_attributes["AlphanumericSerialNumber"]
  prod_name    = product_attributes["ProductName"]
  new_name     = "#{prod_name} (#{alphanumeric})"
  puts '-----------------'
  # I haven't messed with anything in here....
  if edit_bytes
    bytes=edid_hex.scan(/../).map{|x|Integer("0x#{x}")}.flatten

    puts "Setting color support to RGB 4:4:4 only"
    bytes[24] &= ~(0b11000)

    puts "Number of extension blocks: #{bytes[126]}"
    puts "removing extension block"
    bytes = bytes[0..127]
    bytes[126] = 0

    bytes[127] = (0x100-(bytes[0..126].reduce(:+) % 256)) % 256
    puts 
    puts "Recalculated checksum: 0x%x" % bytes[127]
    puts "new EDID:\n#{bytes.map{|b|"%02X"%b}.join}"
  end
  Dir.mkdir("DisplayVendorID-%x" % vendorid) rescue nil
  f = File.open("DisplayVendorID-%x/DisplayProductID-%x" % [vendorid, productid], 'w')
  f.write '<?xml version="1.0" encoding="UTF-8"?>
  <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">
  <plist version="1.0">'
  f.write "
  <dict>
    <key>DisplayProductName</key>
    <string>#{new_name}</string>
    <key>DisplayVendorID</key>
    <integer>#{vendorid}</integer>
    <key>DisplayProductID</key>
    <integer>#{productid}</integer>
  </dict>
  </plist>"
  f.close  
end


  

Attempting to run this script on an M1 Max Macbook Pro with an LG monitor plugged into DisplayPort on a CalDigit dock gives me this:

EDID UUID "1E6D4D77-0000-0000-071F-0104B5582578"
{}
-----------------
edid_rename_display.rb:50:in `%': can't convert nil into Integer (TypeError)
	from edid_rename_display.rb:50:in `block in <main>'
	from edid_rename_display.rb:13:in `each'
	from edid_rename_display.rb:13:in `each_with_index'
	from edid_rename_display.rb:13:in `<main>'