Static analysis to hunt down unused css & js after removing view code. Comment out the haml2html stuff if you are starting with erb/html

find_unused_css_js.rb

# script assumes you have already `git rm app/views/foo/bar.haml`, the more removed code the better

require 'httparty'

# find_deleted_lines
deleted_haml = `git diff --cached --diff-filter=D app/views`

# remove info about which file
cleaned_lines = []
in_head = 0
deleted_haml.each_line do |line|
  if line.match /^diff --git/
    in_head += 1
  end

  case in_head
  when 6
    in_head = 0
  when 1..5
    in_head += 1
  else
    cleaned_lines << line[1..-1]
  end
end

cleaned_lines = cleaned_lines.join
cleaned_lines.gsub! /'/, '"' # make all quotes be double quotes
cleaned_lines.gsub! /^.*No newline at end of file/, '' # we don't care about these messages
cleaned_lines.gsub! /:inlinejavascript/, ":javascript" # custom filter to regular one
opts = {body: {converter: 2, haml: cleaned_lines}}

# convert haml to erb
html = HTTParty.post("https://haml2erb.org/api.html", opts).body

# find_classes
classes = html.to_enum(:scan, /class=['"].+['"]/).map { Regexp.last_match.to_s.gsub(/class=./,'').gsub(/['"]/,'').split(" ") }.flatten.uniq

# find_ids
ids = html.to_enum(:scan, /id=['"].+['"]/).map { Regexp.last_match.to_s.gsub(/id=./,'').gsub(/['"]/,'').split(" ") }

# count stuff and indicate what's safe to remove
{ids: ids, classes: classes}.each do |type, arr|

  other_uses = arr.map {|c| `git grep #{c} app/views`.split("\n").size}

  # count css rules
  css_rules = arr.map {|c| `git grep #{c} app/assets/stylesheets`.split("\n").size}

  # count js uses
  js_uses = arr.map {|c| `git grep #{c} app/assets/javascripts`.split("\n")}.size

  # find classes without other uses but with rules or js

  things_to_remove = []
  arr.each_with_index do |c, i|
    things_to_remove << c if other_uses[i] == 0 && (css_rules[i] > 0 || js_uses[i] > 0)
  end

  if things_to_remove.size > 0
    puts "Try removing the following #{type}:"
    puts ""
    puts things_to_remove
  else
    puts "Looks like all the #{type} are used somewhere else or don't have associated js or css"
  end
end
return nil