☀️ Google Summer of Code 2026: Final Report

Java 25 Language Features Support for Checkstyle

📖 Read the report →

Student	Vivek Singh Solanki
Organisation	Checkstyle
Mentors	Roman Ivanov · Mohamed Mahfouz · Stoyan Kostadinov
Project board	checkstyle/projects/15

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About the project

Java 25 (LTS) finalised language features that Checkstyle could not handle: compact source files (JEP 512) crashed the parser, module import declarations (JEP 511) were ignored by most checks, and the build failed with 100+ test errors on JDK 25. On top of that, module-info.java had never been parseable: the single most requested parsing gap in the project, open since 2020.

Over the summer this project delivered, across checkstyle/checkstyle and its tooling repos:

• 🌳 Grammar support for JEP 512 compact source files and for module-info.java (all JLS 7.7 directives)
• 🔍 Three published feature audits covering every check against the new syntax (JEP 511, JEP 512, modules)
• 🐛 Fixes for every crash and false positive the audits found, plus false-negative fixes and new-token support
• ✅ A CI-enforced coverage test that turns the remaining compact-source work into a machine-verified to-do list
• 🧩 Two new checks, ModuleImportOrder and ModuleDirectiveOrder, plus three more approved proposals
• ⚙️ Green build and CI on JDK 25

53 pull requests raised · 48 merged · 64 issues opened

The full story (what was built, how the scope evolved, and every PR with its status) is in the final report.

Repository layout

├── index.html      landing page
└── 2026/
    ├── index.html  the GSoC 2026 final report
    ├── style.css
    └── script.js

Plain HTML/CSS/JS, no build step, no external dependencies, served with GitHub Pages.

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_{Written as the permanent work-product submission for Google Summer of Code 2026.}