Rack::FirebugLogger

About

Allows logging from your Rack-based app in Firebug (or the WebKit inspector)

firebug_logger.rb

class FirebugLogger
  def initialize(app, options = {})
    @app = app
    @options = options
  end

  def call(env)
    dup._call(env)
  end

  def _call(env)
    status, headers, body = @app.call(env)
    return [status, headers, body] if !(headers["Content-Type"] =~ /html/)
    return [status, headers, body] unless env['firebug.logs']
    response = Rack::Response.new([], status, headers)
    js = generate_js(env['firebug.logs'])
    body.each do |line|
      line.gsub!("</body>", js)
      response.write(line)
    end
    response.finish
  end

  private

  def generate_js(logs)
    js = ["<script>"]
    start_group(js)
    logs.each do |level, log|
      level = sanitise_level(level)
      log.gsub!('"', '\"')
      js << "console.#{level.to_s}(\"#{log}\");"
    end
    end_group(js)
    js << "</script>"
    js.join("\n")
  end

  def start_group(js)
    if @options[:group]
      js << "console.group(\"#{@options[:group]}\");"
    end
  end

  def sanitise_level(level)
    if [:info, :debug, :warn, :error].include?(level)
      level
    else
      :debug
    end
  end

  def end_group(js)
    if @options[:group]
      js << "console.groupEnd();"
    end
  end
end

LICENSE

Copyright (c) 2009 Simon Jefford

Permission is hereby granted, free of charge, to any person
obtaining a copy of this software and associated documentation
files (the "Software"), to deal in the Software without
restriction, including without limitation the rights to use,
copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the
Software is furnished to do so, subject to the following
conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
OTHER DEALINGS IN THE SOFTWARE.

Usage

Currently takes one option when initialised, :group. This allows you to specify the group under which your logs appear - see "Nested grouping" at http://getfirebug.com/logging.html for an example.

To log, set env['firebug.logs'] to a list of pairs. The first element in each pair should be the log level: :info, :warn, :debug or :error. The second element should be the message.

For example

env['firebug.logs'] = [[:info, "beginning"]]
env['firebug.logs'] << [:error, "something went wrong"]