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https://issues.apache.org/jira/browse/MNG-8112?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17929475#comment-17929475
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Christoph Läubrich commented on MNG-8112:
-----------------------------------------
Same behavior / problem on {code}Apache Maven 4.0.0-rc-2
(273314404f85ec3c089e295d8b4e0cb18c287cf5){code}
I use this in my {code}META-INF/maven/extension.xml{code}:
{code}<extension>
<exportedPackages>
<exportedPackage>org.codehaus.plexus.build</exportedPackage>
</exportedPackages>
<exportedArtifacts>
<exportedArtifacts>org.codehaus.plexus:plexus-build-api</exportedArtifacts>
</exportedArtifacts>
</extension>{code}
When the plugin is added with {code}.mvn/extensions.xml{code} then it is
replaced on other mojos and I got this print out:
> [INFO] [stdout] Event listener created by
> ClassRealm[coreExtension>org.codehaus.plexus:plexus-build-api:1.2.1-SNAPSHOT,
> parent: ClassRealm[plexus.core, parent: null]]
When I use instead {code}-Dmaven.ext.class.path=...{code} then it is not
replaced in classpath of mojos and I get
> [INFO] [stdout] Event listener created by ClassRealm[maven.ext, parent:
> ClassRealm[plexus.core, parent: null]]
If I use both ({code}.mvn/extensions.xml{code} and
{code}-Dmaven.ext.class.path=...{code}) then I get it two times:
> [INFO] [stdout] Event listener created by
> ClassRealm[coreExtension>org.codehaus.plexus:plexus-build-api:1.2.1-SNAPSHOT,
> parent: ClassRealm[plexus.core, parent: null]]
> [INFO] [stdout] Event listener created by
> ClassRealm[coreExtension>org.codehaus.plexus:plexus-build-api:1.2.1-SNAPSHOT,
> parent: ClassRealm[plexus.core, parent: null]]
My expectation would be:
# It replaces the jar in the mojos classpath regardless of what technique is
used
# If it is used in multiple places then {code}-Dmaven.ext.class.path=...{code}
takes precedence over {code}.mvn/extensions.xml{code}
> extension.xml is ignored when extension is loaded by -Dmaven.ext.class.path
> ---------------------------------------------------------------------------
>
> Key: MNG-8112
> URL: https://issues.apache.org/jira/browse/MNG-8112
> Project: Maven
> Issue Type: Bug
> Components: Class Loading
> Affects Versions: 3.9.6
> Reporter: Rich DiCroce
> Priority: Major
>
> As the title says: extension.xml is ignored when an extension is loaded by
> -Dmaven.ext.class.path, which makes it impossible to expose any additional
> packages.
> I am filing this as a bug due to [this
> comment|https://issues.apache.org/jira/browse/MNG-6906?focusedCommentId=17719869&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-17719869]
> on MNG-6906, which says that lib/ext and -Dmaven.ext.class.path are supposed
> to be synonymous. Note that MNG-6906 is a related but different problem.
> When looking at org.apache.maven.cli.MavenCli, the problems aren't too hard
> to see:
> # lib/ext extensions get loaded into the plexus.core realm (as per m2.conf),
> but -Dmaven.ext.class.path extensions are loaded into the maven.ext realm (as
> per MavenCli#setupContainerRealm()).
> # loadCoreExtensions() operates on the coreRealm, but due to #1, the
> extensions are not in that realm. Also, the result of parseExtClasspath() is
> not passed to loadCoreExtensions(), so there is no way for
> loadCoreExtensions() to find the relevant files.
> The most obvious solution would be to call coreRealm.addURL() for each of the
> files discovered by parseExtClasspath(). This would solve #1 above which
> would implicitly fix #2. Though I don't know if it would have other
> consequences.
> If this is not a bug and is instead "works as designed", then
> [https://maven.apache.org/guides/mini/guide-using-extensions.html] needs to
> be updated to explain that the three methods of loading core extensions are
> not equivalent.
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