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Interception (intercept + exception) allows you to intercept all exceptions as they are raised.

Installation

As with all rubygems, use gem to install:

gem install interception

Or, if you're using bundler:

source 'https://rubygems.org'
gem 'interception'

Usage

Add and remove listeners. They'll be called whenever an exception is raised (whether or not it would later be rescued) with both the exception object, and the binding from which it was raised. The binding can be used to discover further information about the context.

require 'interception'
listener = lambda{ |exception, binding|
  puts "raised: #{exception.inspect}"
}

Interception.listen(listener)

begin
  raise "oopsy"
rescue => exception
  puts "rescued: #{exception.inspect}"
end

raise "daisy"

Interception.unlisten(listener)

In the common case that you want to listen to events for the duration of a block, you can also pass that block to listen:

require 'interception'
def log_exceptions(&block)
  Interception.listen(block) do |exception, binding|
    puts "raised: #{exception.inspect} from #{binding.eval("__method__")}"
  end
end

def hello
  raise "oopsy"
rescue => exception
  puts "rescued: #{exception.inspect} in #{__method__}"
  raise "daisy"
end

log_exceptions do
  hello
end

Your listen block is run as through it were called by Kernel#raise, so try not to raise an exception from within it, or you will loose the original exception.

Known bugs

  • On rubinius we don't catch some low-level exceptions (like ZeroDivisionError).
  • On MRI-1.8.7, the binding sometimes has the wrong value for self.
  • The Interception versions prior to 0.4 do not support MRI-2.1.0. >= 0.4 does support it.

Meta-fu

Interception is released under the MIT license (see LICENSE.MIT for details). Contributions and bug reports are welcome.