Many JRuby contributors use IntelliJ IDEA for developing JRuby.

Opening the project is as simple as pointing IntelliJ at our Maven pom.xml.

1. Go to File => Open.
2. Browse to your JRuby repository clone.
3. Select pom.xml in the root of the clone and proceed.

IntelliJ will open up the project, read in subprojects, and scan all files. You may be asked to set up Maven auto-updating or a Java SDK.

The easiest way to debug JRuby is to add a run configuration pointing at a known file. Then you can just put the code you want to run in that file and push a button.

1. Go to the Run menu (or the dropdown on the related Toolbar with a play button and a bug on it).
2. Select Edit Configurations.
3. Add a configuration similar to this (adjust settings and all to your preferences):
   1. Click the + to add a configuration.
   2. Add a new "Application" configuration.
   3. Adjust settings.
      • Main class: org.jruby.Main
      • VM options: -Djruby.home=/Users/headius/projects/jruby plus anything else you want.
      • Program arguments: Only requirement is the file to run or a -e line. This is the JRuby command line
      • Working directory: your JRuby clone dir.
      • Use classpath of module: jruby-core
      • Before launch: Maven goal package

You should be able to Run or Debug the given command line with full stepping, inspection, and so on.