ClassNotFoundException: o.e.aether.spi.synccontext.SyncContextFactory cannot be found by o.e.m2.pde.target

[kwin]

I face the following exception when trying to load the target platform for m2e itself:

An internal error occurred during: "Load Target Platform".

java.lang.NoClassDefFoundError: org/eclipse/aether/spi/synccontext/SyncContextFactory
	at org.eclipse.m2e.pde.target.MavenTargetBundle.lambda$2(MavenTargetBundle.java:141)
	at org.eclipse.m2e.core.internal.embedder.MavenExecutionContext.executeBare(MavenExecutionContext.java:394)
	at org.eclipse.m2e.core.internal.embedder.MavenExecutionContext.execute(MavenExecutionContext.java:275)
	at org.eclipse.m2e.core.internal.embedder.MavenExecutionContext.execute(MavenExecutionContext.java:214)
	at org.eclipse.m2e.pde.target.MavenTargetBundle.getWrappedArtifact(MavenTargetBundle.java:136)
	at org.eclipse.m2e.pde.target.MavenTargetBundle.<init>(MavenTargetBundle.java:102)
	at org.eclipse.m2e.pde.target.MavenTargetLocation.addBundleForArtifact(MavenTargetLocation.java:356)
	at org.eclipse.m2e.pde.target.MavenTargetLocation.resolveDependency(MavenTargetLocation.java:265)
	at org.eclipse.m2e.pde.target.MavenTargetLocation.resolveArtifacts(MavenTargetLocation.java:170)
	at org.eclipse.m2e.pde.target.MavenTargetLocation.resolveBundles(MavenTargetLocation.java:157)
	at org.eclipse.pde.internal.core.target.AbstractBundleContainer.resolve(AbstractBundleContainer.java:96)
	at org.eclipse.pde.internal.core.target.TargetDefinition.resolve(TargetDefinition.java:429)
	at org.eclipse.pde.core.target.LoadTargetDefinitionJob.runInWorkspace(LoadTargetDefinitionJob.java:123)
	at org.eclipse.core.internal.resources.InternalWorkspaceJob.run(InternalWorkspaceJob.java:43)
	at org.eclipse.core.internal.jobs.Worker.run(Worker.java:63)
Caused by: java.lang.ClassNotFoundException: org.eclipse.aether.spi.synccontext.SyncContextFactory cannot be found by org.eclipse.m2e.pde.target_2.0.400.20230523-1752
	... 15 more

Any idea what might be wrong? I have the bundle org.eclipse.m2e.maven.runtime in version 3.8.701.20230209-1606. I guess this is the one which is supposed to export that class. Is it too old? If so, why does the PDE bundle doesn't require a newer version then?

[kwin]

It seems that with this change a newer maven runtime is required: 1f6e171. @laeubi Isn't SyncContextFactory not only provided by Maven 3.9 and newer?

[HannesWell]

The same error is emitted in https://github.com/eclipse-m2e/m2e-core/actions/runs/5280667956/jobs/9553119244?pr=1435. Do we no longer support building with Maven < 3.9?

Indeed we don't.
Tycho 4 requires Maven 3.9 or greater, for the same reason m2e.pde.target because it uses the same code to resolve Maven Targets.

[kwin]

Maybe a clearer exception message in Tycho 4 (the build extension) should be emitted.

[laeubi]

Tycho can't do anything here as it is Maven that knows about the runtime, I already asked at the ASF-JIRA how an extension can declare a minimal maven version but got no reply, tycho-maven-plugin itself requires maven 3.9.0 already:

https://github.com/eclipse-tycho/tycho/blob/7fc82e1c95ba1390a0ba0a46240b62e177c239e5/tycho-maven-plugin/pom.xml#L25-L27

[kwin]

The extension can figure out the Maven version and throw a more meaningful exception then.

[laeubi]

This is not really feasible:

1. Each extension needs to replicate some code to figure this out, so it is better done once and for all extensions at the root
2. It is even possible that this code never runs because the extension code fails earlier because of an incompatible maven version.