Re: NPE in MavenProject (3.9.10) in parallel build

It is https://github.com/apache/maven/issues/2487. This affects 3.9.10 but
not 3.9.9 I guess.

On Wed, Jul 2, 2025 at 4:46 PM Laird Nelson <[email protected]> wrote:

> Looks like https://issues.apache.org/jira/browse/MNG-8256 introduced code
> that causes this problem
>
> On Wed, Jul 2, 2025 at 11:57 AM Laird Nelson <[email protected]> wrote:
>
>> 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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