[jira] [Created] (MSHADE-402) Shading produces empty test jar

["Cédric Champeau (Jira)" <ji...@apache.org>]

Cédric Champeau created MSHADE-402:
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             Summary: Shading produces empty test jar
                 Key: MSHADE-402
                 URL: https://issues.apache.org/jira/browse/MSHADE-402
             Project: Maven Shade Plugin
          Issue Type: Bug
    Affects Versions: 3.2.4
            Reporter: Cédric Champeau


Dear maintainers,

I'm working with the shade plugin in the context of a workaround for a Windows bug: when invoking a CLI in Windows, there's a maximum length that you can use. The GraalVM `native-image` is invoked on CLI with a "classpath" argument which easily exceeds that limit. There are several options to workaround this but in this context, the most promising, which worked for the Gradle plugin, was to use _shading_.

For the main artifact, this technique works properly: we can use the "shade" plugin to generate a shaded jar which is then passed to `native-image`. However, we also have support for _unit test_ execution "as a native image", which means that we need to build a native image which includes test classes and the test runtime (e.g JUnit Platform).

Unfortunately, this technique doesn't work for Maven. First of all, let's see how the build is configured:
{code:xml}
<plugin>
   <groupId>org.apache.maven.plugins</groupId>
   <artifactId>maven-shade-plugin</artifactId>
   <version>3.2.4</version>
   <executions>
       <execution>
           <phase>package</phase>
           <goals>
               <goal>shade</goal>
           </goals>
       </execution>
   </executions>
   <configuration>
       <shadedArtifactAttached>true</shadedArtifactAttached>
       <shadeTestJar>true</shadeTestJar>
   </configuration>
</plugin>

{code}
As you can see, I'm using `shadeTestJar`, but if you run the package phase, you will see that the resulting jar is _empty_. After trying to figure out why, it turns out there are 2 different reasons:
 * the first one seems to be that you _must_ generate a test jar before hand. This isn't mentioned in the docs, but I could get a _non empty_ jar by adding this:
{code:xml}
     <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-jar-plugin</artifactId>
        <version>3.2.0</version>
        <executions>
          <execution>
            <goals>
              <goal>test-jar</goal>
            </goals>
          </execution>
        </executions>
      </plugin>
{code}

 * the second problem is that the shaded generated test jar doesn't include the test dependencies

After debugging, I noticed that the `project.getDependencies()` method did **not** return the test dependencies. The javadocs for this method state that they _should_ include the test dependencies, since when this code is executed, the "test" phase has been executed. Debugging showed me that the "resolved dependencies" cache was correct, but that a filter only kept the "runtime" dependencies. The mojo descriptor mentions:

@Mojo( name = "shade", defaultPhase = LifecyclePhase.PACKAGE, threadSafe = true, requiresDependencyResolution = ResolutionScope.RUNTIME )

So I guess the problem comes from the "requiresDependencyResolution" value, which should be set to "TEST" for the test jar to include test dependencies.

However, I suspect that by changing this parameter to TEST, then the _main_ jar would suddenly start including test dependencies, which isn't expected.

Let me know if my analysis is correct. I'm open to suggestions on how to workaround this problem.

Thanks!



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