Maven 4 (rc5) creates effective pom with wrong <project> header

[RalfNaujokat]

Affected version

4.0.0-rc5

Bug description

Hi all.

With a minimal POM

<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://maven.apache.org/POM/4.1.0"
		 xsi:schemaLocation="http://maven.apache.org/POM/4.1.0 http://maven.apache.org/xsd/maven-4.1.0.xsd">
	<modelVersion>4.1.0</modelVersion>


	<groupId>tmp</groupId>
	<artifactId>tmp</artifactId>
	<version>tmp</version>
	<packaging>pom</packaging>


</project>

i noticed, that mvn help:effective-pom
generates a pom with 4.0.0 schemaLocation

Effective POMs, after inheritance, interpolation, and profiles are applied:

<?xml version="1.0" encoding="UTF-8"?>
<!-- ====================================================================== -->
<!--                                                                        -->
<!-- Generated by Maven Help Plugin                                         -->
<!-- See: https://maven.apache.org/plugins/maven-help-plugin/               -->
<!--                                                                        -->
<!-- ====================================================================== -->
<!-- ====================================================================== -->
<!--                                                                        -->
<!-- Effective POM for project 'tmp:tmp:pom:tmp'                            -->
<!--                                                                        -->
<!-- ====================================================================== -->
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.1.0</modelVersion>
  <groupId>tmp</groupId>
  <artifactId>tmp</artifactId>
  <version>tmp</version>
  <packaging>pom</packaging>

  ...

I don't know what are the consequences, but i guess this should be corrected.

greetings
Ralf

[achyuth8055]

Hi @RalfNaujokat , I would like to investigate and work on #11715 issue if it is not currently being handled. I will start by reproducing the issue and analysing how the effective model namespace and schema Location are generated.

[elharo]

There's a deeper issue here. All the 4.0.0 namespaces are incorrect, and not just in these examples.. This should not have been changed from 3.x.

[gnodet]

This issue is related to the broader namespace discussion in #10692 — whether Maven should use a single namespace (http://maven.apache.org/POM/4.0.0) across all model versions or use distinct namespaces per model version. The resolution of that debate will determine whether the current behavior is actually a bug or correct.

Claude Code on behalf of Guillaume Nodet

[RalfNaujokat]

So cool, that you guys found a solution for that issue.
It looks like this was a quite hard one, all in all.

I' looking forward to the first maven 4 version.
Even an improved rc6 would help me a lot.
We (my team at work) really need some clrarification
about the next big thing. :-)