Supporting single responsibility through automated extract method refactoring

TL;DR

This paper introduces a new backward slicing algorithm for refactoring long methods into smaller, single-responsibility methods, improving code quality and refactoring opportunity detection.

Contribution

The paper presents a novel backward slicing algorithm that refactors long methods into independent, single-responsibility methods, enhancing precision and code cohesion.

Findings

29.6% improvement in precision over state-of-the-art

12.1% improvement in recall of refactoring opportunities

20% increase in method-level cohesion metrics

Abstract

The responsibility of a method/function is to perform some desired computations and disseminate the results to its caller through various deliverables, including object fields and variables in output instructions. Based on this definition of responsibility, this paper offers a new algorithm to refactor long methods to those with a single responsibility. We propose a backward slicing algorithm to decompose a long method into slightly overlapping slices. The slices are computed for each output instruction, representing the outcome of a responsibility delegated to the method. The slices will be non-overlapping if the slicing criteria address the same output variable. The slices are further extracted as independent methods, invoked by the original method if certain behavioral preservations are made. The proposed method has been evaluated on the GEMS extract method refactoring benchmark and three real-world projects. On average, our experiments demonstrate at least a 29.6% improvement in precision and a 12.1% improvement in the recall of uncovering refactoring opportunities compared to the state-of-the-art approaches. Furthermore, our tool improves method-level cohesion metrics by an average of 20% after refactoring. Experimental results confirm the applicability of the proposed approach in extracting methods with a single responsibility.