Better Errors

Better Errors replaces the standard Rails error page with a much better and more useful error page. It is also usable outside of Rails in any Rack app as Rack middleware.

Features

• Full stack trace
• Source code inspection for all stack frames (with highlighting)
• Local and instance variable inspection
• Live REPL on every stack frame

Installation

Add this to your Gemfile:

group :development do
  gem "better_errors"
end

NOTE: It is critical you put better_errors in the development section. Do NOT run better_errors in production, or on Internet facing hosts.

If you would like to use Better Errors' advanced features (REPL, local/instance variable inspection, pretty stack frame names), you need to add the binding_of_caller gem to your Gemfile:

gem "binding_of_caller"

This is an optional dependency however, and Better Errors will work without it.

Usage

If you're using Rails, there's nothing else you need to do.

If you're not using Rails, you need to insert BetterErrors::Middleware into your middleware stack, and optionally set BetterErrors.application_root if you'd like Better Errors to abbreviate filenames within your application.

Here's an example using Sinatra:

require "sinatra"
require "better_errors"

use BetterErrors::Middleware
BetterErrors.application_root = File.expand_path("..", __FILE__)

get "/" do
  raise "oops"
end

Open-in-Editor functionality

File links will open in TextMate by default, using the txmt URL scheme. You can supply a custom proc to generate the URL for your preferred editor :

BetterErrors.editor = Proc.new{|file, line| "mvim://open/?url=file://#{URI.escape file}&line=#{line}"}

Compatibility

• Supported
  • MRI 1.9.2, 1.9.3
  • JRuby (1.9 mode) - advanced features unsupported
  • Rubinius (1.9 mode) - advanced features unsupported
• Coming soon
  • MRI 2.0.0 - the official API for grabbing caller bindings is slated for MRI 2.0.0, but it has not been implemented yet

Known issues

• Calling yield from the REPL segfaults MRI 1.9.x.

Get in touch!

If you're using better_errors, I'd love to hear from you. Drop me a line and tell me what you think!

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request