AntiCopyPaster: Extracting Code Duplicates As Soon As They Are Introduced in the IDE

TL;DR

AntiCopyPaster is an IDE plugin that detects code duplicates early during development, recommending refactorings to improve code quality, with high accuracy and positive developer feedback.

Contribution

It introduces a novel IDE-integrated approach with a classification model to proactively suggest refactorings for code duplicates.

Findings

Correctly recommends refactorings with an F-score of 0.82

Achieves high developer satisfaction in surveys

Operates effectively on large datasets from real projects

Abstract

We developed a plugin for IntelliJ IDEA called AntiCopyPaster, which tracks the pasting of code fragments inside the IDE and suggests the appropriate Extract Method refactoring to combat the propagation of duplicates. Unlike the existing approaches, our tool is integrated with the developer's workflow, and pro-actively recommends refactorings. Since not all code fragments need to be extracted, we develop a classification model to make this decision. When a developer copies and pastes a code fragment, the plugin searches for duplicates in the currently opened file, waits for a short period of time to allow the developer to edit the code, and finally inferences the refactoring decision based on a number of features. Our experimental study on a large dataset of 18,942 code fragments mined from 13 Apache projects shows that AntiCopyPaster correctly recommends Extract Method refactorings with an F-score of 0.82. Furthermore, our survey of 59 developers reflects their satisfaction with the developed plugin's operation. The plugin and its source code are publicly available on GitHub at https://github.com/JetBrains-Research/anti-copy-paster. The demonstration video can be found on YouTube: https://youtu.be/_wwHg-qFjJY.