Start a pry session whenever something goes wrong.
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README.md
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pry-rescue.gemspec

README.md

pry-rescue helps you quickly figure out why your code broke; when an exception is raised that would normally kill your program, Pry comes to the rescue, opening a Pry session in the context of code that raised the exception.

Installation

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

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

Usage

There are two ways to use pry-rescue:

Wrap an entire script

Use the launcher script:

rescue <script.rb> [arguments..]

Wrap a block in your code

In development, wrap your code in Pry::rescue{ }; then any exceptions that are raised but not rescued will open a pry session. This is particularly useful for debugging servers and other long-running processes.

require 'pry-rescue'

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

Pry.rescue 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)>

cd-cause

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 ...

try-again

Once you've used Pry's edit or edit-method commands to fix your code, you can issue a try-again command to re-run your code. (Either from the start in the case of using the rescue script, or from the block if you're using that API).

[1] pry(main)> edit-method
[2] pry(main)> whereami
From: examples/example.rb @ line 4 Object#test:

    4: def test
 => 5:   puts "foo"
    6: rescue => e
    7:   raise "bar"
    8: end
[3] pry(main)> try-again
foo

pry-stack explorer

If you're running rubinius, or ruby-1.9, then you can use pry-rescue 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.