_asset_exception_pages.md

In order to use asset pipeline available for static error pages (like 404.html), a few steps are required

• Move static pages from /public into /app/assets

  (eg: public/422.html → app/assets/html/422.html.erb)

• Add html directory to the asset pipeline

• Update exceptions middleware to understand assets with digests

application.rb

# config/application.rb

module MyApp
  class Application < Rails::Application
  
    # HTML Assets
    config.assets.paths << Rails.root.join('app/assets/html')
    config.assets.register_mime_type('text/html', '.html')

    config.assets.precompile += %w( .html )
 end
end
  

exceptions.rb

# config/initializers/exceptions.rb
# http://devoh.com/blog/2012/09/asset-pipeline-error-pages

module ActionDispatch
  class PublicAssetExceptions < PublicExceptions

    def render_html(status)
      found = false
      path = "#{public_path}/#{status}.#{I18n.locale}.html" if I18n.locale
      path = "#{public_path}/#{status}.html" unless path && (found = File.exist?(path))

      unless path && (found = File.exist?(path))
        status_file = "#{status}.html"
        asset_status_file = ActionController::Base.helpers.asset_digest_path(status_file)
        path = "#{public_path}/#{asset_status_file}"
      end

      if found || File.exist?(path)
        render_format(status, 'text/html', File.read(path))
      else
        [404, { "X-Cascade" => "pass" }, []]
      end
    end
  end
end

MyApp::Application.configure do
  config.middleware.swap(
    ActionDispatch::ShowExceptions,
    ActionDispatch::ShowExceptions,
    ActionDispatch::PublicAssetExceptions.new(   #if your sprockets is configured to generate non-digest files
      Rails.root.join('public/assets')           #it is not necessary to derive from PublicExceptions, you can just use those
    )
  )
end

test_asset_404_spec.rb

#don't forget the tests
feature 'Static Pages' do
  scenario 'should show a nice 404 page' do
    Rails.application.config.consider_all_requests_local = false
    Rails.application.config.action_dispatch.show_exceptions = true

    visit "/asdfasf"

    page.should have_content("Sorry, that page doesn't exist")
    page.driver.status_code.should == 404
  end
end

based on http://devoh.com/blog/2012/09/asset-pipeline-error-pages

Thanks, @ilyakatz. Came across this when trying to fix error handling in the app I based my blog post on. 😉