SLE-1443 Migrate to Java 21 for the backend

[damien-urruty-sonarsource]

No description provided.

[hashicorp-vault-sonar-prod]

SLE-1443

[sonar-review-alpha]

Summary

This PR is a comprehensive infrastructure migration and project restructuring for SonarLint Eclipse. It upgrades the version to 12.0.0 and establishes the project's CI/CD pipeline with GitHub Actions workflows, adds testing infrastructure for multiple Eclipse/Java versions (including Java 21 support), and refactors the build system. The changes include 1,088 files with ~66K insertions, establishing root-level Maven configuration, GitHub Actions workflows (build, release, PR management, security scanning), build automation scripts, target platform definitions for testing, and a complete integration test suite with test project templates.

What reviewers should know

Start here:

• Review .github/workflows/build.yml - this is the main CI/CD pipeline; note the test matrix includes latest-java-21 target platform alongside 11 and 17
• Check pom.xml (root) - establishes parent project version 12.0.0 and Maven configuration; source/target remain Java 11 for compatibility
• Review target-platforms/*.target files - defines Eclipse/Java combinations for testing; latest-java-21.target is the new Java 21 target

Key architectural decisions:

• Minimum Java version stays at 11, but CI now tests against Java 21 via Tycho target platforms (this allows the plugin to run on newer Java while maintaining compatibility)
• Maven 3 + Tycho 4.0.12 build system; uses mise for JDK management
• Extensive integration test framework in its/ directory with separate test modules for different scenarios (standalone, connected mode, CDT, etc.)

Non-obvious elements:

• sloop.version property (11.0.0.85168) in pom.xml ties the embedded SonarLint Core version - verify this is correct
• GitHub workflows include expensive matrix builds across 4+ configurations - watch for CI time/cost
• .github/scripts/ contains critical build scripts (Maven toolchain setup, version management) - pay attention to conditional logic and environment setup
• Integration tests use RedDeer for UI automation and require Xvfb display server - infrastructure-heavy
• Version bump to 12.0.0 is significant; confirm this aligns with release strategy

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🗣️ Give feedback

[thahnen]

Overall, I give this a 💯
I see SLE in good hands with you, much love and merci 🥳

[kirill-knize-sonarsource]

LGTM. Couple nits on error logging.

[sonar-review-alpha]

LGTM! ✅

Solid PR. The Java 21 migration is clean — preference key rename with a well-tested migration path, version detection via the release file, and startup/preference-page warnings all hang together correctly. The timeout fix in SonarLintBackendService (join() → get(1, TimeUnit.MINUTES)) is the headline reliability improvement and is handled correctly including interrupt restoration. No bugs found beyond the previously acknowledged self-managed JRE validation gap.

🗣️ Give feedback

[sonarqube-next]

Quality Gate passed

Issues
0 New issues
0 Fixed issues
2 Accepted issues

Measures
0 Security Hotspots
0 Dependency risks
47.4% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube