pry-capture allows you to start a Pry session on any unhandled exceptions in your code.

Installation

Either gem install pry-capture, or add it to the development section of your Gemfile:

source :rubygems
group :development do
  gem 'pry-capture'
  gem 'pry-stack_explorer' # if you're using MRI 1.9 and you want it to be awesome.
end

Usage

In development, wrap your code in Pry::capture{ }; then any exceptions that are raised but not rescued will open a pry session.

require 'pry-capture'

def test
  raise "foo"
rescue => e
  raise "bar"
end

Pry.capture do
  test
end

This will land you in a pry-session:

From: examples/example.rb @ line 4 Object#test:

    4: def test
    5:   raise "foo"
    6: rescue => e
 => 7:   raise "bar"
    8: end

RuntimeError: bar
from examples/example.rb:7:in `rescue in test'
[1] pry(main)>

If you need to find the reason that the exception happened, you can use the cd-cause command:

[1] pry(main)> cd-cause
From: examples/example.rb @ line 4 Object#test:

    4: def test
 => 5:   raise "foo"
    6: rescue => e
    7:   raise "bar"
    8: end

RuntimeError: foo
from examples/example.rb:5:in `test'
[1] pry(main)>

To get back from cd-cause you can either type <ctrl+d> or cd ...

pry-stack explorer

If you're running rubinius, or ruby-1.9, then you can use pry-capture alongside pry-stack_explorer. This gives you the ability to move up or down the stack so that you can get a better idea of why your function ended up in a bad state. Run example2.rb to get a feel for what this is like.

Known bugs

Occasionally, when using ruby-1.8 or jruby, the value for self will be incorrect. You will still be able to access local variables, but calling methods will not work as you expect.

On rbx we are unable to intercept some exceptions thrown from inside the C++ VM, for example the ZeroDivisionError in 1 / 0.

Meta-fu

Released under the MIT license, see LICENSE.MIT for details. Contributions and bug-reports are welcome.