NullPointerException @ ClirrReportGenerator.java:64

[mpkorstanje]

While running mvn clean site -X with the following configuration for clirr

<reporting>
    <plugins>
        <plugin>
            <groupId>org.codehaus.mojo</groupId>
            <artifactId>clirr-maven-plugin</artifactId>
            <version>2.7</version>
        </plugin>
    </plugins>
</reporting>

I run into the following null pointer exception.

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-site-plugin:3.3:site (default-site) on project simmetrics-core: Execution default-site of goal org.apache.maven.plugins:maven-site-plugin:3.3:site failed. NullPointerException -> [Help 1]
org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-site-plugin:3.3:site (default-site) on project simmetrics-core: Execution default-site of goal org.apache.maven.plugins:maven-site-plugin:3.3:site failed.
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:224)
    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:862)
    at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:286)
    at org.apache.maven.cli.MavenCli.main(MavenCli.java:197)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    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-site of goal org.apache.maven.plugins:maven-site-plugin:3.3:site failed.
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:145)
    at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
    ... 20 more
Caused by: java.lang.NullPointerException
    at org.codehaus.mojo.clirr.ClirrReportGenerator$ApiChangeComparator.compare(ClirrReportGenerator.java:64)
    at org.codehaus.mojo.clirr.ClirrReportGenerator$ApiChangeComparator.compare(ClirrReportGenerator.java:57)
    at java.util.TimSort.binarySort(TimSort.java:292)
    at java.util.TimSort.sort(TimSort.java:235)
    at java.util.Arrays.sort(Arrays.java:1438)
    at java.util.List.sort(List.java:478)
    at java.util.Collections.sort(Collections.java:175)
    at org.codehaus.mojo.clirr.ClirrReportGenerator.doApiChangesTable(ClirrReportGenerator.java:600)
    at org.codehaus.mojo.clirr.ClirrReportGenerator.doApiChanges(ClirrReportGenerator.java:453)
    at org.codehaus.mojo.clirr.ClirrReportGenerator.generateReport(ClirrReportGenerator.java:186)
    at org.codehaus.mojo.clirr.ClirrReport.doReport(ClirrReport.java:316)
    at org.codehaus.mojo.clirr.ClirrReport.generate(ClirrReport.java:227)
    at org.codehaus.mojo.clirr.ClirrReport.generate(ClirrReport.java:363)
    at org.apache.maven.plugins.site.ReportDocumentRenderer.renderDocument(ReportDocumentRenderer.java:228)
    at org.apache.maven.doxia.siterenderer.DefaultSiteRenderer.renderModule(DefaultSiteRenderer.java:319)
    at org.apache.maven.doxia.siterenderer.DefaultSiteRenderer.render(DefaultSiteRenderer.java:135)
    at org.apache.maven.plugins.site.SiteMojo.renderLocale(SiteMojo.java:175)
    at org.apache.maven.plugins.site.SiteMojo.execute(SiteMojo.java:138)
    at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
    ... 21 more

If I knew what API changed caused it I'd provide a minimal example. Best I can do currently is provide my current project:

https://github.com/Simmetrics/simmetrics/tree/feature-v4.0.0

Call with mvn clean site -P reports -X

[AnEmortalKid]

I ran into this same issue too, I think it happens when you have new stuff in a file (https://github.com/mojohaus/clirr-maven-plugin/blob/master/src/main/java/org/codehaus/mojo/clirr/ClirrReportGenerator.java). I think the from for the ApiChange gets initialized to null.

If it helps any, I reverted back to 2.6.2 and things started building.

[brandonheck]

I'm also running into this issue. Strangely, running the clirr goal by itself (mvn org.codehaus.mojo:clirr-maven-plugin:2.7:clirr) succeeds.

The change that I'm seeing show up (which I expect) is that a protected method was removed from a class. I don't suspect this to be the cause, however, since running the goal stand-alone succeeds.

[brandonheck]

I take that back; I think I had bumped my dependency version down (per the suggestion from @AnEmortalKid) and then tried running the stand-alone goal without cleaning the directory.

I think I may have found the root cause: I have a class that changed to an enum (went from Java 4 to Java 6) and the Message id is 5000, which it looks like the plugin doesn't recognize.

I can't guarantee that this is what is causing the NPE, but definitely looks suspicious.

[brandonheck]

If I remove the clirr-maven-plugin from the build section and run the standalone clirr goal (only configured in the reporting section in the pom), it succeeds! The plot thickens...

[brandonheck]

Debugging more, it is definitely related to the Message id 5000 (added class to superclasses). The APIChange does not have a from because the APIDifference for that does not have an affected method or affected field.

APIChange is new with version 2.7 and seems to be the root of the problem, as it only handles method and field changes, but not a subset of the other changes that clirr-core recognizes.