Open-source projects struggle to configure code quality tools correctly

<p>Background: Static Code Analysis (SCA) tools are widely adopted to enforce code quality standards. However, little is known about how open-source projects use and customize these tools. Aims: This paper investigates how GitHub projects use and customize a popular SCA tool, namely SonarQube Cloud.</p><p>Method: We conducted a mining study of GitHub projects that are linked through GitHub Actions to SonarQube Cloud projects.</p><p>Results: Among 321 GitHub projects using SonarQube Cloud, 81% of them are correctly connected to SonarQube Cloud projects, while others exhibit misconfigurations or restricted access. Among 265 accessible SonarQube Cloud projects, 75% use the organization's default quality gate, i.e., a set of conditions that deployed source code must meet to pass automated checks. While 55% of the projects use the built-in quality gate provided by SonarQube Cloud, 45% of them customize their quality gate with different conditions. Overall, the most common quality conditions align with SonarQube Cloud's 'Clean as You Code' principle and enforce security, maintainability, reliability, coverage, and a few duplicates on newly added or modified source code.</p><p>Conclusions: Many projects rely on predefined configurations, yet a significant portion customize their configurations to meet specific quality goals. Building on our initial results, we envision a future research agenda linking quality gate configurations to actual software outcomes (e.g., improvement of software security). This would enable evidence-based recommendations for configuring SCA tools like SonarQube Cloud in various contexts. </p>