In order to develop IntelliJ IDEA plugins, you can use either IntelliJ IDEA Community Edition or IntelliJ IDEA Ultimate - both of them include the complete set of plugin development tools.
In order to set up the plugin development environment, you should follow these steps:
- Check out the sources of IntelliJ IDEA Community Edition as described in Check Out & Build Community Edition
- Create an SDK of type "IntelliJ IDEA SDK" and specify your installation of IntelliJ IDEA Community Edition as the home path. (You can use IDEA Ultimate as well, but debugging the core code will only work with the Community Edition.)
- In the Sourcepath tab of the SDK settings, press the "Add..." button and specify the directory into which you have checked out the sources of the Community Edition
- Create a new module of type "Plugin" and select the created SDK as the SDK to be used for this module.
After that, you can develop your plugin in the same way as before - with the added possibility to see the source code of all the core and trace its execution in the debugger.
The documentation for developing plugins can be found at the Confluence site at http://www.jetbrains.net/confluence/display/IDEADEV/PluginDevelopment .