vendor/rails/activesupport/lib/active_support/backtrace_cleaner.rb

   1 module ActiveSupport
   2   # Many backtraces include too much information that's not relevant for the context. This makes it hard to find the signal
   3   # in the backtrace and adds debugging time. With a BacktraceCleaner, you can setup filters and silencers for your particular
   4   # context, so only the relevant lines are included.
   5   #
   6   # If you need to reconfigure an existing BacktraceCleaner, like the one in Rails, to show as much as possible, you can always
   7   # call BacktraceCleaner#remove_silencers!
   8   #
   9   # Example:
  10   #
  11   #   bc = BacktraceCleaner.new
  12   #   bc.add_filter   { |line| line.gsub(Rails.root, '') }
  13   #   bc.add_silencer { |line| line =~ /mongrel|rubygems/ }
  14   #   bc.clean(exception.backtrace) # will strip the Rails.root prefix and skip any lines from mongrel or rubygems
  15   #
  16   # Inspired by the Quiet Backtrace gem by Thoughtbot.
  17   class BacktraceCleaner
  18     def initialize
  19       @filters, @silencers = [], []
  20     end
  21
  22     # Returns the backtrace after all filters and silencers has been run against it. Filters run first, then silencers.
  23     def clean(backtrace)
  24       silence(filter(backtrace))
  25     end
  26
  27     # Adds a filter from the block provided. Each line in the backtrace will be mapped against this filter.
  28     #
  29     # Example:
  30     #
  31     #   # Will turn "/my/rails/root/app/models/person.rb" into "/app/models/person.rb"
  32     #   backtrace_cleaner.add_filter { |line| line.gsub(Rails.root, '') }
  33     def add_filter(&block)
  34       @filters << block
  35     end
  36
  37     # Adds a silencer from the block provided. If the silencer returns true for a given line, it'll be excluded from the
  38     # clean backtrace.
  39     #
  40     # Example:
  41     #
  42     #   # Will reject all lines that include the word "mongrel", like "/gems/mongrel/server.rb" or "/app/my_mongrel_server/rb"
  43     #   backtrace_cleaner.add_silencer { |line| line =~ /mongrel/ }
  44     def add_silencer(&block)
  45       @silencers << block
  46     end
  47
  48     # Will remove all silencers, but leave in the filters. This is useful if your context of debugging suddenly expands as
  49     # you suspect a bug in the libraries you use.
  50     def remove_silencers!
  51       @silencers = []
  52     end
  53
  54
  55     private
  56       def filter(backtrace)
  57         @filters.each do |f|
  58           backtrace = backtrace.map { |line| f.call(line) }
  59         end
  60
  61         backtrace
  62       end
  63
  64       def silence(backtrace)
  65         @silencers.each do |s|
  66           backtrace = backtrace.reject { |line| s.call(line) }
  67         end
  68
  69         backtrace
  70       end
  71   end
  72 end