Some will argue that Duplication is the worst coding sin because it perpetuates all the others. For instance, copying and pasting a block of code duplicates its Bugs and Potential Bugs, its Coding Standards Breaches, and so on. It's a meta-sin, if you will.

To help you detect and eliminate duplication, SonarQube uses its own copy/paste detection engine, which can detect duplications:

Looking For Duplications

Add the Duplications widget (was Comments & Duplications prior to version 3.7) to your dashboard:

From there, you can drill down to the Duplications perspective in the component viewer:

 

How to read the example above: 

To display the source of a particular instance of a block, click on the file name.

To visualize the entire block of code, click on the Expand link.

Activating Cross Module and Cross Project Duplication Detection

By default, the scope of duplication detection is the project for standard projects and the module for multi-module projects. To detect duplications between the modules of your project and between the different projects analyzed on your SonarQube platform, log in as a a System administrator, go to Settings > General Settings > General > Duplications and set the Cross project duplication detection property to true. Then run another analysis on your projects.

Notes:

Best Practices

Related Topics

See the following blog post: Manage Duplicated Code with Sonar.