pry + raise = praise

A small gem intercepting all #raise calls spawning pry sessions to investigate. There is runtime-editable config file to set ignore patterns for unwanted raise calls. The gem is targeting investigation of re-risen and masked-by-another exceptions.

Difference between prise and pry-rescue

Praise allows a developer to investigate all exceptions including the ones rescued later. pry-rescue on the other hand will work only for exceptions which are un-handled by the process. Typical use-case is e.g. a worker, which is rescuing all exceptions. pry-rescue cannot help with investigation of these exceptions.


  1. require the gem early, e.g. in contig/application.rb in rails
  2. install Praise, e.g.

    Praise = PraiseImpl.
        new(File.join(root, Katello.early_config.praise.ignored_path),
            -> level, message { Logging.logger['praise'].add Logging.level_num(level), message })

And that's it.


Whenever an exception is risen and exception is not ignored then you will be dropped to a Pry session.

From: /Users/pitr/Workspace/personal/praise/lib/praise.rb @ line 75 Kernel#raise:

    64: define_method :raise do |*args|
    65:   begin
    66:     message             = args.find { |o| o.kind_of? String }
    67:     backtrace           = args.find { |o| o.kind_of? Array }
    68:     exception_generator = args.find { |o| ![message, backtrace].include? o } || RuntimeError
    69:     exception           = message ? exception_generator.exception(message) : exception_generator.exception
    70:     message             ||= exception.message
    71:     risen_at            = caller(1).first
    73:     unless Thread.current[:__pry_in_rescue__] || praise.ignore?(exception, message, risen_at)
    74:       Thread.current[:__pry_in_rescue__] = true
 => 75:       binding.pry
    76:     end
    78:     _original_raise *args
    79:   ensure
    80:     Thread.current[:__pry_in_rescue__] = false
    81:   end
    82: end

[1] pry(#<Delayed::Backend::ActiveRecord::Job>)>

Stack can be explored with pry-stack_explorer plugin for Pry:

pry-stack_explorer (v0.4.9)
  down               Go down to the callee's context.
  frame              Switch to a particular frame.
  show-stack         Show all frames
  up                 Go up to the caller's context.

Use up or frame 1 to get to the binding and line where the exception was risen. When you hit C-d exception is risen as usual.


If there were no method to ignore some exceptions, It would drop to pry for every single #raise call, which would not be very useful. Therefore there is a yml file where filters can be specified to ignore exceptions. It can be updated at runtime PraiseImpl#add_rule.

Ignore file structure

[{ class:   'AClass' },         # exception ignored when exception.class.to_s == 'AClass'
 { message: /missing plugin/ }, # exception ignored when exception.message =~ /missing plugin/
 { line:    /rubygems/ },       # exception ignored when risen_at =~ /rubygems/
 { class:   RuntimeError, message: /nothing/ }
 # exception ignored when both rules are met