Fix copy and unpack for artifacts with unavailable parents

[brunoborges]

Maven Dependency Plugin 3.11.0 made artifact descriptor resolution mandatory for copy and unpack, which prevents otherwise available artifacts from being processed when their POM references an unavailable snapshot parent.

This change preserves descriptor-based relocation support, but scopes a fallback to the from-configuration goals: when descriptor reading fails, the original artifact coordinates are resolved directly. Artifact resolution failures still fail the goal and retain the descriptor exception as suppressed context.

A repository-backed integration test reproduces the unavailable snapshot-parent case, and focused resolver coverage verifies the fallback. Existing copy and unpack relocation integration tests continue to pass.

Fixes: #1642

[Copilot]

Pull request overview

This PR restores dependency:copy / dependency:unpack usability for artifacts whose POM descriptor resolution fails due to an unavailable parent POM, by introducing a controlled fallback that resolves the original artifact coordinates directly (while still preferring descriptor-based relocation when available).

Changes:

• Add ResolverUtil.resolveArtifactWithFallback(...) to fall back to direct resolution when readArtifactDescriptor fails, preserving the original descriptor exception as suppressed context if resolution still fails.
• Wire the fallback into from-configuration goals via AbstractFromConfigurationMojo#getArtifact.
• Add unit coverage for the fallback path and an integration test project/repository artifact that reproduces the missing-parent scenario.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/main/java/org/apache/maven/plugins/dependency/utils/ResolverUtil.java	Introduces fallback artifact resolution and extracts a direct-resolve helper.
src/main/java/org/apache/maven/plugins/dependency/fromConfiguration/AbstractFromConfigurationMojo.java	Switches from descriptor-mandatory resolution to fallback-enabled resolution for configured artifact items.
src/test/java/org/apache/maven/plugins/dependency/utils/ResolverUtilTest.java	Adds a resolver unit test covering descriptor-failure fallback behavior.
src/it/projects/copy-broken-parent/pom.xml	Adds an IT project exercising dependency:copy against an artifact with a missing parent POM.
src/it/projects/copy-broken-parent/invoker.properties	Defines invoker goals for the new IT project.
src/it/projects/copy-broken-parent/verify.groovy	Verifies the copied artifact is produced in the expected location.
src/it/mrm/repository/broken-parent-artifact-1.0.pom	Adds a mock repository artifact whose parent is intentionally unavailable to reproduce the regression.

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[elharo]

Test failures might be related:

Warning: Could not transfer metadata /.meta/prefixes.txt from/to jvnet-nexus-releases (https://maven.java.net/content/repositories/releases/): (certificate_expired) PKIX path validation failed: java.security.cert.CertPathValidatorException: validity check failed
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 8.227 s
[INFO] Finished at: 2026-07-19T10:01:50Z
[INFO] ------------------------------------------------------------------------
Error: Failed to execute goal org.apache.maven.plugins:maven-checkstyle-plugin:3.6.0:check (checkstyle-check) on project maven-dependency-plugin: Failed during checkstyle configuration: Exception was thrown while processing /home/runner/work/maven-dependency-plugin/maven-dependency-plugin/src/test/java/org/apache/maven/plugins/dependency/utils/ResolverUtilTest.java: IllegalStateException occurred while parsing file /home/runner/work/maven-dependency-plugin/maven-dependency-plugin/src/test/java/org/apache/maven/plugins/dependency/utils/ResolverUtilTest.java. 130:93: mismatched input '(' expecting ';': InputMismatchException -> [Help 1]

[ascheman]

Thanks for the fix — the fallback design is sound: descriptor-based resolution first (so relocation is preserved), with a scoped fallback to the original coordinates only on ArtifactDescriptorException, keeping the descriptor exception as suppressed context. Limiting it to the from-configuration goals is the right call.

The CI failure isn't the expired jvnet-nexus-releases certificate — that's an unrelated infra warning. It's a genuine syntax error in the new test: src/test/java/org/apache/maven/plugins/dependency/utils/ResolverUtilTest.java is missing a closing brace. resolveArtifactWithFallbackWhenDescriptorCannotBeRead() ends with the two verify(...) calls and then a single } at column 0, which closes the method but leaves the class body unclosed (5 { vs 4 }). That's what makes checkstyle fail with mismatched input '(' expecting ';' — and it won't compile either. Adding the method's closing brace fixes it:

        verify(repositorySystem).resolveArtifact(eq(repositorySystemSession), any(ArtifactRequest.class));
    }
}

Two smaller, non-blocking notes:

• The reproducer only exercises dependency:copy. Since the fix also targets unpack, an unpack IT against an artifact with an unavailable parent would lock the fallback in end-to-end for both goals.
• Copilot's "assert readArtifactDescriptor was invoked" is already covered — the test has verify(repositorySystem).readArtifactDescriptor(...).

Requesting changes for the missing brace; the rest looks good once CI is green.

[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated no new comments.

[ascheman]

The blocking issue from my earlier review — the missing closing brace in ResolverUtilTest — is fixed in 972d2da, and the full CI matrix is green. The fallback design is sound: descriptor-first (so relocation is preserved), with a scoped fallback to the original coordinates only on ArtifactDescriptorException, limited to the from-configuration goals. Approving.

Non-blocking follow-up (fine to do post-merge): the IT only exercises dependency:copy; an unpack IT against an artifact with an unavailable parent would lock the fallback in end-to-end for both goals.

[brunoborges]

@ascheman done!

tests passing