How to debug Maven plugin?

Question

I use allure-maven plugin configured in my POM. However, when it fails with

ru.yandex.qatools.allure.data.ReportGenerationException: Could not find any allure results

I would like to debug the plugin at runtime to see if it has all variables set properly.

I have tried to use mvnDebug as per answers to Debugging in Maven?. I am able to connect with a debugger to JVM when Maven executes tests with surefire plugin. However, when Maven tries to generate Allure report with allure plugin I am not able to connect with a debugger. Allure plugin is defined in "reporting" section of the POM and used by the "site" Maven goal.

Here's POM (almost complete, I ommited dependenies section) that I call with mvn clean test site command.

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
             xmlns="http://maven.apache.org/POM/4.0.0"
             xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    ...  

    <build>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.20</version>
                <configuration>
                    <testFailureIgnore>true</testFailureIgnore>
                    <argLine>-Xmx2048m -XX:-UseSplitVerifier -XX:MaxPermSize=256m
                        -javaagent:${settings.localRepository}/org/aspectj/aspectjweaver/${aspectj.version}/aspectjweaver-${aspectj.version}.jar
                    </argLine>
                    <properties>
                        <property>
                            <name>parallel</name>
                            <value>classes</value>
                        </property>
                        <property>
                            <name>threadcount</name>
                            <value>4</value>
                        </property>
                    </properties>
                </configuration>
                <dependencies>
                    <dependency>
                        <groupId>org.aspectj</groupId>
                        <artifactId>aspectjweaver</artifactId>
                        <version>${aspectj.version}</version>
                    </dependency>
                </dependencies>
            </plugin>
        </plugins>
    </build>


    <reporting>
        <excludeDefaults>true</excludeDefaults>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-surefire-report-plugin</artifactId>
                <version>2.19.1</version>
            </plugin>
            <plugin>
                <groupId>io.qameta.allure</groupId>
                <artifactId>allure-maven</artifactId>
                <version>2.8</version>
                <configuration>
                </configuration>
            </plugin>
        </plugins>
    </reporting>

    <pluginRepositories>
        <pluginRepository>
            <id>mvn-nexus-all</id>
            <url>https://lunabuild.akamai.com/nexus/content/groups/public/</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </pluginRepository>
    </pluginRepositories>
</project>

And here's full stacktrace from the failing plugin:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-site-plugin:3.3:site (default-site) on project sso-config-tests: Error during page generation: Error rendering Maven report: Could not generate the report: InvocationTargetException: Could not find any allure results -> [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 sso-config-tests: Error during page generation
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:216)
        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.MojoExecutionException: Error during page generation
        at org.apache.maven.plugins.site.SiteMojo.execute(SiteMojo.java:143)
        at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:134)
        at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:208)
        ... 20 more
Caused by: org.apache.maven.doxia.siterenderer.RendererException: Error rendering Maven report: Could not generate the report
        at org.apache.maven.plugins.site.ReportDocumentRenderer.renderDocument(ReportDocumentRenderer.java:233)
        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)
        ... 22 more
Caused by: org.apache.maven.reporting.MavenReportException: Could not generate the report
        at ru.yandex.qatools.allure.report.AllureGenerateMojo.executeReport(AllureGenerateMojo.java:127)
        at org.apache.maven.reporting.AbstractMavenReport.generate(AbstractMavenReport.java:255)
        at org.apache.maven.plugins.site.ReportDocumentRenderer.renderDocument(ReportDocumentRenderer.java:219)
        ... 26 more
Caused by: java.lang.reflect.InvocationTargetException
        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 ru.yandex.qatools.allure.report.AllureGenerateMojo.executeReport(AllureGenerateMojo.java:123)
        ... 28 more
Caused by: ru.yandex.qatools.allure.data.ReportGenerationException: Could not find any allure results
        at ru.yandex.qatools.allure.data.AllureReportGenerator.generate(AllureReportGenerator.java:58)
        at ru.yandex.qatools.allure.data.AllureReportGenerator.generate(AllureReportGenerator.java:53)
        at ru.yandex.qatools.allure.AllureMain.main(AllureMain.java:48)
        ... 33 more

Answer 1

If you start your build with mvnDebug clean install instead of mvn clean install Maven will wait for a remote debugger to connect on port 8000. This should work for all plugin that to not run in their own JVM.

This requires Maven greater than 2.0.8 which I assume you are running.

See Debugging in Maven?

Answer 2

If you want to debug it from Intellij IDEA. I assume that you run bundled mvn, JDK9+

1. Go to Maven Runner settings in IDEA.
2. In VM Options specify this line: -agentlib:jdwp=transport=dt_socket,address=5005,server=y,suspend=y

Maven will not proceed up to the moment you connect with remote debugger.

3. Create Remote debugger configuration (specify port 5005).
4. Run remote debugger (do not forget to add breakpoints in code).