ladybug is a visual debugger for Ruby web applications that uses Chrome Devtools as a user interface.

It aims to provide a rich backend debugging experience in a UI that many web developers are already familiar with for debugging frontend Javascript.

This project is currently in an experimental phase. Expect many limitations and bugs. If you try it out, please file Github issues or email me to help make this a more useful tool.

1. Install the gem, or add it to your Gemfile:

gem install ladybug

2. ladybug is implemented as a Rack middleware, so you'll need to add Ladybug::Middleware to the Rack middleware stack. For example, in Rails 5, add the following line to config/application.rb:

config.middleware.use(Ladybug::Middleware)

3. Make sure you're using the puma web server, which is currently the only server that ladybug has been tested with.

To use puma in Rails: add gem 'puma' to your Gemfile and bundle install.

4. Then start up your server and try making a request. You should see your server program output something like:

Debug in Chrome: chrome-devtools://devtools/bundled/inspector.html?ws=localhost:3000

5. Navigate to that URL, and you'll see a Chrome Devtools window. In the Sources tab, you can view your Ruby source code. If you set a breakpoint and then make another request to your server, it should pause on the breakpoint and you'll be able to inspect local and instance variables in Devtools.

6. You can then use the "step over" button to step through your code, or "continue" to continue code execution. "Step into" and "Step out" also work in some contexts.

Security warning: This debugger should only be run in local development. Running it on a server open to the internet could allow anyone to execute code on your server without authenticating.

• So far, ladybug has been tested with simple Rails applications running on Rails 5 with the puma web server. Eventually it aims to support more Rack applications and web servers (and perhaps even non-Rack applications).
• inspecting primtive objects like strings and numbers works okay; support for more complex objects is in development.

@geoffreylitt