arXiv subjects

Jonhnanthan Oliveira

Publications and source records attributed to Jonhnanthan Oliveira.

5 recordsLinked to original sources

arXiv2026

Foundation Models as Oracles for Refactoring Correctness Detection

Refactoring tools in popular Integrated Development Environments (IDEs) can introduce unintended behavioral changes or compilation errors, a persistent challenge that undermines developer trust in automated transformations. Traditional detection approaches rely on handcrafted preconditions, and static and dynamic analyses, yet remain limited in adaptability and can miss subtle correctness issues. This study examines the potential of foundation models to serve as oracles for detecting refactoring bugs in Java programs. We evaluate zero-shot prompting, without task-specific training, across 226 real refactoring bugs collected over more than a decade from widely used Java IDEs (IntelliJ-IDEA, Eclipse, and NetBeans), spanning 47 refactoring types. Our results indicate that foundation models can be effective for this task, although performance varies across models. In the first-run setting, GPT-OSS-20B achieved 80.5% accuracy, while GPT-5.4 reached 93.8%. We also evaluated other open-weight and proprietary models: Gemma-4-31B achieved the strongest result among open-weight models, and Gemini-3.1-Pro-Preview achieved the best overall result among all evaluated models. Metamorphic testing indicates that model predictions remain largely consistent under the tested semantics-preserving perturbations, but these results should be interpreted as robustness evidence rather than as evidence against memorization or data contamination. Beyond detection accuracy, foundation models can provide short explanations that may help support developer inspection, operate across refactoring types without explicitly encoded refactoring-specific rules, and may serve as lightweight triage aids in development workflows. Our findings suggest that foundation models can complement traditional refactoring checks by flagging suspicious transformations for developer inspection.

cs.SE↗

arXiv2026

Detecting Behavioral Changes in Python Refactoring Implementations with Foundation Models

Python is a widely adopted programming language, valued for its simplicity and flexibility. However, automated refactoring for Python remains challenging, even though refactoring is an essential practice in software evolution aimed at improving internal code structure without changing external behavior. Understanding how behavioral changes are introduced during refactoring is crucial, as such issues can compromise software reliability and reduce developer productivity. We propose an approach based on a foundation model oracle that analyzes git-style diffs to identify behavioral changes introduced by Python refactorings. We evaluated our technique on Rope refactoring implementations, reusing 1,152 refactoring attempts from a prior study and analyzing 217 resulting transformation pairs with the oracle. Our model-based analysis uncovered 13 distinct bugs among the seven refactoring types studied. All reported bugs were submitted to the respective developers, and 12 of the 13 resulting issue reports were accepted according to issue-tracker evidence. These results highlight the need to improve the robustness of current Python refactoring tools to ensure the correctness of automated code transformations and support reliable software maintenance.

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arXiv2025

RefModel: Detecting Refactorings using Foundation Models

Refactoring is a common software engineering practice that improves code quality without altering program behavior. Although tools like ReExtractor+, RefactoringMiner, and RefDiff have been developed to detect refactorings automatically, they rely on complex rule definitions and static analysis, making them difficult to extend and generalize to other programming languages. In this paper, we investigate the viability of using foundation models for refactoring detection, implemented in a tool named RefModel. We evaluate Phi4-14B, and Claude 3.5 Sonnet on a dataset of 858 single-operation transformations applied to artificially generated Java programs, covering widely-used refactoring types. We also extend our evaluation by including Gemini 2.5 Pro and o4-mini-high, assessing their performance on 44 real-world refactorings extracted from four open-source projects. These models are compared against RefactoringMiner, RefDiff, and ReExtractor+. RefModel is competitive with, and in some cases outperform, traditional tools. In real-world settings, Claude 3.5 Sonnet and Gemini 2.5 Pro jointly identified 97% of all refactorings, surpassing the best-performing static-analysis-based tools. The models showed encouraging generalization to Python and Golang. They provide natural language explanations and require only a single sentence to define each refactoring type.

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arXiv2025

Bugs in the Shadows: Static Detection of Faulty Python Refactorings

Python is a widely adopted programming language, valued for its simplicity and flexibility. However, its dynamic type system poses significant challenges for automated refactoring - an essential practice in software evolution aimed at improving internal code structure without changing external behavior. Understanding how type errors are introduced during refactoring is crucial, as such errors can compromise software reliability and reduce developer productivity. In this work, we propose a static analysis technique to detect type errors introduced by refactoring implementations for Python. We evaluated our technique on Rope refactoring implementations, applying them to open-source Python projects. Our analysis uncovered 29 bugs across four refactoring types from a total of 1,152 refactoring attempts. Several of these issues were also found in widely used IDEs such as PyCharm and PyDev. All reported bugs were submitted to the respective developers, and some of them were acknowledged and accepted. These results highlight the need to improve the robustness of current Python refactoring tools to ensure the correctness of automated code transformations and support reliable software maintenance.

cs.SE↗

arXiv2025

Evaluating the Effectiveness of Small Language Models in Detecting Refactoring Bugs

Popular IDEs frequently contain bugs in their refactoring implementations. Ensuring that a transformation preserves a program's behavior is a complex task. Traditional detection methods rely on predefined preconditions for each refactoring type, limiting their scalability and adaptability to new transformations. These methods often require extensive static and dynamic analyses, which are computationally expensive, time-consuming, and may still fail to detect certain refactoring bugs. This study evaluates the effectiveness of Small Language Models (SLMs) in detecting two types of refactoring bugs in Java and Python: (i) transformations that introduce errors or behavioral changes (Type I) and (ii) transformations unnecessarily blocked by IDEs despite being valid (Type II). We assess whether Llama 3.2 3B, Mistral 7B, Gemma 2 9B, Gemma 3 12B, DeepSeek-R1 14B, Phi-4 14B, o1-mini, and o3-mini-high can accurately detect 100 refactoring bugs reported in widely used Java and Python IDEs, such as Eclipse and NetBeans. The study covers 16 refactoring types and employs zero-shot prompting on consumer-grade hardware to evaluate the models' ability to reason about refactoring correctness without explicit prior training. The proprietary o3-mini-high model achieved the highest detection rate, identifying 84.3% of Type I bugs. The open-source Phi-4 14B performed comparably well, demonstrating strong effectiveness across both bug types. However, o3-mini-high struggled with Type II bugs, correctly identifying and applying valid but blocked transformations in only 40% of cases. The findings highlight the potential of SLMs for efficiently detecting refactoring bugs, particularly in verifying behavioral changes. Additionally, SLMs offer a more adaptable solution capable of generalizing across different refactoring types and programming languages, addressing key limitations of traditional approaches.

cs.SE↗