Rake pre_deploy task for pre-compiling rails and ember assets, then updating the rails manifest file to point to ember-cli fingerprinted assets

pre_deploy.rake

require 'fileutils'

namespace :wildland do
  namespace :pre_deploy do
    namespace :precompile_assets do
      task :rails do
        system('RAILS_ENV=production bundle exec rake assets:precompile')
      end

      task :ember do
        Dir.chdir('ember') do
          sh 'DISABLE_FINGERPRINTING=false ./node_modules/.bin/ember build --environment=production'
        end
      end

      task :combine do
        FileUtils.rm_r('public/assets/admin_panel', force: true)
        FileUtils.cp_r('ember/dist/assets', 'public/assets/admin_panel')

        rails_manifest = Manifest.new(rails_assets_manifest_path)
        ember_manifest = Manifest.new(ember_assets_manifest_path)
        combine_manifests(rails_manifest, ember_manifest)

        FileUtils.rm(ember_assets_manifest_path)
        File.open(rails_assets_manifest_path, "w") do |f|
          f.write(rails_manifest.manifest.to_json)
        end
      end

      task all: [:rails, :ember, :combine]
    end

    task precompile_assets: ['precompile_assets:all']
  end

  task pre_deploy: ['pre_deploy:precompile_assets'] do
    Rake::Task['wildland:pre_deploy:precompile_assets'].invoke
  end
end

class Manifest
  attr_reader :manifest

  def initialize(path)
    @manifest = JSON.parse(File.read(path))
  end

  def assets
    manifest['assets']
  end

  def files
    manifest['files']
  end
end

def ember_assets_manifest_path
  Dir["public/assets/admin_panel/manifest.json"].first || Dir["public/assets/admin_panel/manifest*.json"].first
end

def rails_assets_manifest_path
  Dir["public/assets/.sprockets-manifest.json"].first || Dir["public/assets/.sprockets-manifest*.json"].first
end

def combine_manifests(rails_manifest, ember_manifest)
  ember_manifest.assets.each_pair do |key, value|
    prefix_path = "admin_panel\/"
    non_fingerprinted_filepath = "#{prefix_path}#{key}"
    fingerprinted_filepath = "#{prefix_path}#{value}"

    if rails_manifest.assets.has_key?(non_fingerprinted_filepath)
      files_fingerprinted_key = rails_manifest.assets[non_fingerprinted_filepath]
      rails_manifest.files.delete(files_fingerprinted_key)
    end

    rails_manifest.assets[non_fingerprinted_filepath] = fingerprinted_filepath
    rails_manifest.files[fingerprinted_filepath] = ember_manifest.files[value].clone
    rails_manifest.files[fingerprinted_filepath]['logical_path'] = non_fingerprinted_filepath
  end
end

https://gist.github.com/Samsinite/b3ab6da492952bf94573