gnodet opened a new pull request, #12529:
URL: https://github.com/apache/maven/pull/12529
## Summary
Adds an integration test demonstrating the **"compile for 3, enhance for
4"** plugin pattern — a Maven plugin that:
- Compiles against Maven 3.9.x API (`maven-plugin-api`, `maven-core`)
- Optionally uses Maven 4's typed API (`Session`, `Project`) at runtime
- Falls back gracefully on Maven 3 — no crashes, no Maven 4 data leaks
### Architecture
```
ProjectInfoMojo.java ← NO Maven 4 imports (loads on Maven 3)
│
│ try { Maven4Enhancer.tryEnhance(...) }
│ catch (NoClassDefFoundError) { /* Maven 3 path 1 */ }
│
├── Maven4Enhancer.java ← imports Session, Project (real typed API)
└── MavenRuntimeDetector.java ← one reflection call for
MavenSession.getSession() bridge
```
### Key design points
- **One reflection call**: only `MavenSession.getSession()` uses reflection
— it's the bridge method added by Maven 4's compat module that doesn't exist on
Maven 3
- **Everything else is typed**: `session.getMavenVersion()`,
`session.getRootDirectory()`, `session.getProjects()`, etc. — direct,
compile-time checked
- **Two Maven 3 fallback paths**:
1. `NoClassDefFoundError` — Maven 4 API classes absent from classpath
2. API jar resolved from Central but `getSession()` bridge absent —
handled in `tryEnhance()`
### Verified on both runtimes
| Runtime | `[MVN3]` tags | `[MVN4]` tags | Detection |
|---------|:-----------:|:-----------:|-----------|
| Maven 3.9.16 | ✅ all 5 | ✅ none | `[RUNTIME] Maven 3` |
| Maven 4.1.0-SNAPSHOT | ✅ all 5 | ✅ all 10 | `[RUNTIME] Maven 4` |
## Test plan
- [x] IT passes on Maven 4 (`mvn verify -Prun-its
-Dits.test=MavenITDualApiPluginTest`)
- [x] Plugin builds and runs correctly on Maven 3.9.16 (manual test)
- [x] No `[MVN4]` data emitted on Maven 3
- [x] All `[MVN4]` data emitted on Maven 4
🤖 Generated with [Claude Code](https://claude.com/claude-code)
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