discourse/lib/middleware/missing_avatars.rb

module Middleware

  # In development mode, it is common to use a database from a production site for testing
  # with their data. Unfortunately, you can end up with dozens of missing avatar requests
  # due to the files not being present locally. This middleware, only enabled in development
  # mode, will replace those with an appropriate image.
  class MissingAvatars
    def initialize(app, settings = {})
      @app = app
    end

    def call(env)
      if (env['REQUEST_PATH'] =~ /^\/uploads\/default\/avatars/)
        path = "#{Rails.root}/public#{env['REQUEST_PATH']}"
        unless File.exist?(path)
          default_image = "#{Rails.root}/public/images/d-logo-sketch-small.png"
          return [ 200, { 'Content-Type' => 'image/png' }, [ File.read(default_image)] ]
        end
      end

      status, headers, response = @app.call(env)
      [status, headers, response]
    end
  end

end