Enable consumer POM flattening for Maven 4 RC-6 readiness - #2647
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Since apache/maven#11780 (first shipping with 4.0.0-rc-6), installing or deploying a POM-packaged project whose model cannot be downgraded to 4.0.0 fails fast. The PLC4X parent uses 4.1.0-only features (subprojects, build sources), so every 'mvn install' will break on RC-6 without maven.consumer.pom.flatten=true. With flattening enabled, jar module consumer POMs become self-contained model-4.0.0 (no parent reference), which also fixes Maven 3/Gradle consumption of published artifacts (apache/maven#11772). Verified with 4.0.0-rc-5 (current wrapper pin) and a current 4.0.0-SNAPSHOT: full reactor builds green with both. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
sruehl
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Jul 20, 2026
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thx for the PR |
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Heads-up: PLC4X will stop building with Maven 4.0.0-RC-6
Since apache/maven#11780 (backported to 4.0.x via #12236, so first shipping with RC-6),
install/deployof a POM-packaged project fails fast when its consumer POM cannot be downgraded to model 4.0.0. The PLC4X parent uses 4.1.0-only features (<subprojects>, build<sources>), so with a current4.0.0-SNAPSHOT(pre-RC-6) every build dies in the very first reactor module:Fix
One line in
.mvn/maven.config:-Dmaven.consumer.pom.flatten=true.Side benefit beyond staying buildable: with flattening enabled, the jar module consumer POMs become self-contained model-4.0.0 (no
<parent>reference), which fixes Maven 3/Gradle consumption of published PLC4X artifacts — the very issue behind apache/maven#11772 (rc-5 silently publishes model-4.1.0 parent POMs that Maven 3/Gradle cannot parse).Verified locally
4.0.0-rc-5(current wrapper pin): full reactorBUILD SUCCESS— property exists and is safe on rc-54.0.0-SNAPSHOT(pre-RC-6): full reactor (113 modules)BUILD SUCCESS; without this change: fail-fast as aboveFound while testing PLC4X against pre-RC-6 Maven for the Maven 4 adoption effort — happy to keep sending such findings your way if useful. 🙏
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