Add Kotlin-in-Maven-project skill

[e5l]

Summary

• Adds kotlin-tooling-add-kotlin-to-maven-project skill that guides configuring Kotlin in existing Java Maven projects
• Uses kotlin-maven-plugin with <extensions>true</extensions> for minimal, clean mixed Java-Kotlin builds
• Includes analysis script (scripts/analyze-maven-project.sh), verification checklist, and compiler plugins reference (Spring, JPA, serialization)

What the skill covers

• Adding kotlin.version property and kotlin-maven-plugin with extensions
• Test dependency setup (junit-jupiter-engine, kotlin-test-junit5)
• Directory structure options (co-located .kt alongside .java vs separate kotlin/ dirs)
• Multi-module Maven project guidance
• Common issues and troubleshooting

Test plan

• Tested against kotlin-junit-sample initial/ project
• With-skill agent produced pom.xml closely matching expected complete/ output
• Without-skill baseline used verbose old-style config (65+ extra XML lines, missed junit-jupiter-engine)
• Build passed with 26 tests (Java + Kotlin) in both runs
• Analysis script correctly detects configured vs unconfigured projects

🤖 Generated with Claude Code

[Tapchicoma]

Asked @shinkai-tester to verify this skill

[d-ambatenne]

Discussed with Leonid, this skill is common for any Maven projects, not only for KSS

[shinkai-tester]

Tested on two projects (used Claude Code):

• https://github.com/spring-projects/spring-petclinic (single-module)
• https://github.com/spring-petclinic/spring-petclinic-microservices (multi-module, 8 modules)

What works well:

• Migration succeeds on both single-module and multi-module projects
• Both source layouts work (src/main|test/java and src/main|test/kotlin)
• Cross-language references compile in both directions (Kotlin→Java and Java→Kotlin)
• All tests pass

Issues found:

1. The smart defaults the skill relies on - automatic kotlin-stdlib dependency and source directory registration via extensions set to true - require Kotlin 2.3.20 or later (not yet available). With the hardcoded 2.1.20 (Step 1: Add Kotlin Version Property), these features won't work. Maybe the skill should instruct the agent to fetch the latest stable version from https://mvnrepository.com/artifact/org.jetbrains.kotlin/kotlin-maven-plugin, and instruct that the minimum should be 2.3.20.
2. "Compiler Plugins (Optional)" heading is misleading for Spring/JPA projects. The "(Optional)" label led the agent to skip compiler plugins on the first pass - but for Spring Boot + JPA projects, the spring and jpa plugins are effectively required. Suggestion: either remove "(Optional)" or reword to something like "Compiler Plugins (Framework-Dependent)" with clearer guidance that this step is required for Spring/JPA projects.

[e5l]

@shinkai-tester, fixed comments. please check it out

[shinkai-tester]

@shinkai-tester, fixed comments. please check it out

@e5l sorry for the delay, just got back from vacation. Looks good 👍