More sane backtraces

Example.md

sane_backtraces.rb

# Shortens filepaths, colorizes the lines that run with the application and
# excludes everything else unless you specify USE_LONG_BACKTRACES=true.
# We have this in: spec/sane_backtraces.rb, loaded from spec_helper.rb.

# Rspec shortens expectation errors when you don't use --backtrace, but not
# runtime errors like a missing method.

class Exception
  USE_LONG_BACKTRACES = ENV['USE_LONG_BACKTRACES']

  alias_method :old_message, :message
  def message
    shorten_and_colorize_paths(old_message)
  end

  alias_method :old_inspect, :inspect
  def inspect
    shorten_and_colorize_paths(old_inspect)
  end

  alias_method :old_backtrace, :backtrace
  def backtrace
    data = old_backtrace

    if data
      if caller.first.match(/rspec.+read_failed_line/)
        data
      else
        backtrace = data.map { |line| shorten_and_colorize_paths(line) }

        if USE_LONG_BACKTRACES
          backtrace
        else
          backtrace = backtrace.reject { |line| !/\[app\]/.match(line) }

          # We can't be sure what is shown, rspec shortens too for expectation failures.
          # So because of this it's "might be shortened"
          backtrace << dark_gray_text("Backtrace might be shortened (set USE_LONG_BACKTRACES=true to disable)")
          backtrace
        end
      end
    else
      nil
    end
  end

  private

  APP_ROOT = File.expand_path(File.join(File.dirname(__FILE__), '..'))

  def shorten_and_colorize_paths(line)
    line = line.gsub(/.+\.rvm.+gems/, '[gem]').
                gsub(APP_ROOT, "[app]").
                gsub(/.+\.rvm\/rubies\/.+?\//, "[ruby]/").
                gsub(/:in/, "")

    if line.include?('[app]')
      green_text(line)
    else
      line
    end
  end

  def dark_gray_text(text)
    "\e[01;30m#{text}\e[00m"
  end

  def green_text(text)
    "\e[00;32m#{text}\e[00m"
  end
end