[jira] [Commented] (MNG-6732) DefaultArtifactDescriptorReader.loadPom to check IGNORE_MISSING policy upon ArtifactTransferException

["Michael Osipov (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/MNG-6732?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17017533#comment-17017533 ] 

Michael Osipov commented on MNG-6732:
-------------------------------------

I was able to make your test project run according to the instructions.

> DefaultArtifactDescriptorReader.loadPom to check IGNORE_MISSING policy upon ArtifactTransferException
> -----------------------------------------------------------------------------------------------------
>
>                 Key: MNG-6732
>                 URL: https://issues.apache.org/jira/browse/MNG-6732
>             Project: Maven
>          Issue Type: Improvement
>          Components: core
>    Affects Versions: 3.6.1
>            Reporter: Tomo Suzuki
>            Assignee: Michael Osipov
>            Priority: Major
>             Fix For: 3.7.0-candidate
>
>         Attachments: 62884438-89260580-bd04-11e9-8c4a-897d4b736dc7.png
>
>          Time Spent: 0.5h
>  Remaining Estimate: 0h
>
> h1. Problem
> Sometimes [Linkage Checker enforcer rule|https://github.com/GoogleCloudPlatform/cloud-opensource-java/tree/master/enforcer-rules] does not receive resolved artifact list because of a missing artifact even when the missing artifact is unused after Maven's dependency mediation.
> h1. Background
> The enforcer rule fails to retrieve artifact list through {{DefaultProjectDependenciesResolver.resolve}} when applied to [grpc-java-by-example/chat-example/chat-vaadin-client|https://github.com/saturnism/grpc-java-by-example/tree/master/chat-example/chat-vaadin-client] because of the missing {{xerces:xerces-impl:2.6.2}}, even though the artifact does not appear in the final dependency graph. The artifact does not appear in the graph because of Maven's dependency mediation.
> Artifact xerces:xerces-impl:2.6.2 is not published in Maven Central.
> In contrast, the enforcer rule can retrieve artifact list when applied to [https://github.com/suztomo/spring-cloud-gcp/tree/v1.1.2-linkage-checker] project even though it outputs "[WARNING] The POM for xerces:xerces-impl:jar:2.6.2 is missing, no dependency information available". The missing artifact does not appear in final dependency graph.
> [https://github.com/GoogleCloudPlatform/cloud-opensource-java/issues/834]
> h1. Diagnosis
> Currently {{DefaultArtifactDescriptorReader.loadPom}} method checks "ArtifactDescriptorPolicy.IGNORE_MISSING" policy upon ArtifactNotFoundException. This allows {{DefaultProjectDependenciesResolver.resolve}} calls {{repoSystem.resolveDependencies}} to obtain partially resolved artifact list, rather than failing entirely, when there is a missing artifact (such as {{xerces:xerces-impl:2.6.2}})
> However, when a retired Maven repository is involved (such as [http://repository.codehaus.org/] ), {{DefaultArtifactDescriptorReader.loadPom}} gets an ArtifactTransferException and throws ArtifactDescriptorException without checking "ArtifactDescriptorPolicy.IGNORE_MISSING" policy (excerpt below), and thus {{DefaultProjectDependenciesResolver.resolve}} does not return partially resolved artifact list.
> {code:java}
>             catch ( ArtifactResolutionException e )
>             {
>                 if ( e.getCause() instanceof ArtifactNotFoundException )
>                 {
>                     missingDescriptor( session, trace, a, (Exception) e.getCause() );
>                     if ( ( getPolicy( session, a, request ) & ArtifactDescriptorPolicy.IGNORE_MISSING ) != 0 )
>                     {
>                         return null;
>                     }
>                 }
>                 result.addException( e );
>                 throw new ArtifactDescriptorException( result );
>             }
> {code}
> from [DefaultArtifactDescriptorReader.java|https://github.com/apache/maven/blob/d3ace78/maven-resolver-provider/src/main/java/org/apache/maven/repository/internal/DefaultArtifactDescriptorReader.java#L255]
> ArtifactNotFoundException is a special case of [ArtifactTransferException|https://maven.apache.org/resolver/apidocs/org/eclipse/aether/transfer/ArtifactTransferException.html].
> h1. Example Project
> Example project to demonstrate the diagnosis: [https://github.com/suztomo/maven-missing-artifact] . In this example, even though module-b and module-c have the same dependency section, module-c fails to run Maven because of a repository section containing a retired repository URL.



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