compile tests using maven-compiler and jdk9-ea+148

Question

I have problem with building my application using maven-compile-plugin:3.6.0 at jdk9-ea+148.

I am trying to make jdk9 module. Module-info and other classes are getting compiled without problem, but when it comes to default-testCompile it just crashes. When my module-info.java is removed, the it is compiled without problems.

Basically this is the exception I am getting:

Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.6.0:testCompile (default-testCompile) on project bar: Execution default-testCompile of goal org.apache.maven.plugins:maven-compiler-plugin:3.6.0:testCompile failed. NullPointerException -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.6.0:testCompile (default-testCompile) on project bar: Execution default-testCompile of goal org.apache.maven.plugins:maven-compiler-plugin:3.6.0:testCompile failed.
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:212)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:153)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:145)
        at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:116)
        at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
        at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:51)
        at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:128)
        at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:307)
        at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:193)
        at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:106)
        at org.apache.maven.cli.MavenCli.execute(MavenCli.java:863)
        at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:288)
        at org.apache.maven.cli.MavenCli.main(MavenCli.java:199)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.base/java.lang.reflect.Method.invoke(Method.java:538)
        at org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:289)
        at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:229)
        at org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:415)
        at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:356)
Caused by: org.apache.maven.plugin.PluginExecutionException: Execution default-testCompile of goal org.apache.maven.plugins:maven-compiler-plugin:3.6.0:testCompile failed.
        at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:145)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:207)
        ... 20 more
Caused by: java.lang.NullPointerException
        at org.apache.maven.plugin.compiler.AsmModuleInfoParser.getModuleName(AsmModuleInfoParser.java:48)
        at org.apache.maven.plugin.compiler.TestCompilerMojo.preparePaths(TestCompilerMojo.java:259)
        at org.apache.maven.plugin.compiler.AbstractCompilerMojo.execute(AbstractCompilerMojo.java:742)
        at org.apache.maven.plugin.compiler.TestCompilerMojo.execute(TestCompilerMojo.java:164)
        at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
        ... 21 more

This is the settings of maven-compiler-plugin I have there

<plugins>
 <plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-compiler-plugin</artifactId>
  <version>3.6.0</version>
  <configuration>
   <source>1.9</source>
   <target>1.9</target>
   <compilerArgument>-Xlint:all</compilerArgument>
  </configuration>
 </plugin>
</plugins>

Does anyone know what to do with this problem to make it work?

Answer 1

The exception occurs when Maven tries to read the module-info.classs class name, which since a recent change was specified to be null. It looks like Maven uses ASM and according to Remi Forax ASM6 should already handle that case.

I suggest looking for an issue in the Maven issue tracker and open one if it can't be found.

Answer 2

Using the updated version of the maven-compiler-plugin:3.7.0 shall help you fix this:-

<plugins>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-compiler-plugin</artifactId>
        <version>3.7.0</version>
        <configuration>
            <source>9</source>
            <target>9</target>
            <compilerArgument>-Xlint:all</compilerArgument>
        </configuration>
     </plugin>
</plugins>

Answer 3

I had the same problem with maven-compile-plugin:3.6.0 at jdk9-ea+149.

I noticed that the actual root cause for this was the test directory not having a module-info.java file (I had only added one to the src directory). As soon as I added a module-info file, the problem went away.

That said, I don't have a clue how the jigsaw directory/module structure should be laid out regarding unit tests - if tests are in a separate module, they can only access the public (exported) API.