Re: NPE in MavenProject (3.9.10) in parallel build

Will do. It's certainly possible, I guess, in 3.9.10.

Here's one place the non-volatile artifacts instance field is set:
https://github.com/apache/maven/blob/maven-3.9.10/maven-core/src/main/java/org/apache/maven/project/MavenProject.java#L661

Here's another:
https://github.com/apache/maven/blob/maven-3.9.10/maven-core/src/main/java/org/apache/maven/project/MavenProject.java#L1457

And another:
https://github.com/apache/maven/blob/maven-3.9.10/maven-core/src/main/java/org/apache/maven/project/MavenProject.java#L1471

So if for some reason any of those happens, then this:
https://github.com/apache/maven/blob/maven-3.9.10/maven-core/src/main/java/org/apache/maven/project/MavenProject.java#L683

…might be null. We're still trying to figure out how to reproduce this in a
tidy manner; in the meantime my prior message shows the bug tripping in one
of our (public) CI runs.

On Tue, Jul 1, 2025 at 4:32 AM Elliotte Rusty Harold <[email protected]>
wrote:

> That shouldn't be possible, at least not with the code I see at head.
> Please file a bug though a reproducible test case might be required to
> do anything about this.
>
> On Tue, Jul 1, 2025 at 1:26 AM Laird Nelson <[email protected]> wrote:
> >
> > Curious if people have seen this NPE before:
> >
> https://github.com/helidon-io/helidon/actions/runs/15985949089/job/45090504083?pr=10313#step:3:9789
> >
> > We're running with -T8 (
> >
> https://github.com/helidon-io/helidon/actions/runs/15985949089/job/45090504083?pr=10313#step:3:166
> ).
> > (Github Actions.)
> >
> > Relevant snippet:
> >
> > Caused by: java.lang.NullPointerException: Cannot invoke
> > "java.util.Set.add(Object)" because "this.artifacts" is null
> > at org.apache.maven.project.MavenProject.getArtifacts
> > (MavenProject.java:683)
> > at org.apache.maven.plugins.javadoc.AbstractJavadocMojo.getPathElements
> > (AbstractJavadocMojo.java:2491)
> > at org.apache.maven.plugins.javadoc.AbstractJavadocMojo.addJavadocOptions
> > (AbstractJavadocMojo.java:4550)
> > at org.apache.maven.plugins.javadoc.AbstractJavadocMojo.executeReport
> > (AbstractJavadocMojo.java:1968)
> >
> > The fact that it was javadocs I think may be immaterial. It is certainly
> > the case that MavenProject is not thread safe. Maybe that's by design?
> > Should I file a bug?
> >
> > Best,
> > Laird
>
>
>
> --
> Elliotte Rusty Harold
> [email protected]
>
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