Fix: preserve original trace data when stamping re-entrancy marker

[gnodet]

Summary

PR #1957 (commit e29d0cd) added re-entrancy detection to DefaultRepositorySystem by stamping a REPOSITORY_SYSTEM_CALL marker into the RequestTrace chain. However, it placed the marker as the trace tip data, replacing whatever was there before (typically an Artifact set by Maven core).

Plugins that walk the RequestTrace chain and cast getData() to their expected type without an instanceof check (e.g. pgpverify-maven-plugin, maven-gpg-plugin) get a ClassCastException:

ClassCastException: class org.eclipse.aether.internal.impl.DefaultRepositorySystem$1 
cannot be cast to class org.apache.maven.artifact.Artifact

This is a regression — both maven-artifact-plugin and maven-gpg-plugin were passing with rc-5 and are now failing with resolver 2.0.21-SNAPSHOT.

Fix

Instead of placing the marker as the trace tip, insert it one level deeper and re-attach the original tip data on top:

private static RequestTrace stampReentrancyMarker(RequestTrace currentTrace) {
    RequestTrace markerTrace = RequestTrace.newChild(currentTrace, REPOSITORY_SYSTEM_CALL);
    return currentTrace != null
            ? RequestTrace.newChild(markerTrace, currentTrace.getData())
            : markerTrace;
}

The isReentrant() method is unaffected — it walks the full chain and will still find the marker.

Test plan

• Added outerCallPreservesOriginalTraceData test verifying that original trace data remains at the tip after stamping
• Added outerCallWithNullTraceStillStampsMarker test verifying the null-trace case still works correctly for re-entrancy detection
• All existing re-entrancy tests continue to pass
• Full maven-resolver-impl test suite passes (454 tests, 0 failures)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR fixes a regression in DefaultRepositorySystem re-entrancy detection by stamping the REPOSITORY_SYSTEM_CALL marker into the RequestTrace chain without overwriting the original trace tip data (which is commonly an Artifact provided by Maven core). This avoids downstream ClassCastExceptions in plugins that assume the trace tip’s getData() is of a specific type.

Changes:

• Introduce stampReentrancyMarker(RequestTrace) to insert the marker below the trace tip while preserving the original tip data.
• Update all relevant public DefaultRepositorySystem entrypoints to use stampReentrancyMarker(...) instead of stamping the marker as the trace tip.
• Add tests covering preservation of original trace tip data and the null-trace stamping/re-entrancy behavior.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
maven-resolver-impl/src/main/java/org/eclipse/aether/internal/impl/DefaultRepositorySystem.java	Replace direct marker stamping with stampReentrancyMarker(...) to preserve original RequestTrace tip data.
maven-resolver-impl/src/test/java/org/eclipse/aether/internal/impl/DefaultRepositorySystemReentrancyTest.java	Add regression tests for trace tip preservation and null-trace marker stamping behavior.

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