Developed a Vue data-declaration best-practice lint rule for the biomejs/biome repository, focusing on enforcing function-based data declarations in Vue 3+ components to prevent shared mutable state. The rule, implemented under analyze/js, automatically converts object data declarations into functions returning the data object, streamlining code consistency and reducing manual intervention. This work centered on static code analysis and automated code repair, leveraging JavaScript, TypeScript, and linting expertise. By addressing a common source of runtime bugs and improving maintainability, the contribution enhanced onboarding and code quality across projects. No major bugs were fixed during this period, with efforts dedicated to tooling improvements.