In this project, we develop and build AntiCopyPaster — an IntelliJ plugin that tracks the pasting of code inside the IDE and suggests appropriate Extract Method refactorings to combat the propagation of duplicates. To implement the plugin, we gathered a dataset of code fragments that should and should not be extracted, compiled a list of metrics of code that can influence the decision, and trained several popular classifying machine learning models, of which Random Forest showed the best results. When a developer pastes a code fragment, the plugin searches for duplicates in the currently opened file. If there are any, it waits for a short period of time to allow the developer to edit the code. If the code duplicates are still present after a delay, AntiCopyPaster calculates the metrics for the fragment and inferences the decision: if the fragment should be extracted, the plugin suggests to refactor it.
The plugin is available on GitHub.