Question about argLine set to empty

[Roberto Andrioli]

Hey Guys,

I have another question about JaCoCo. 

Why is JaCoCo plugin setting argLine to empty when the plugin execution is skipped? Why simply does nothing? i.e., do not change argLine.

I come with this question after setup a simple Maven project. In this project I have a Java agent configured in the argLine directly in properties section:

```

<properties>

    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>

    <argLine>-javaagent:lib/my-custom-agent.jar -Doutput.file=target/output.bin</argLine>

</properties>

```

JaCoCo plugin prepend its own configuration in the argLine and Surefire runs everything perfectly. But when JaCoCo plugin is skipped, the argLine is set to empty and my custom agent do not run.

I know, I can easily fix this issue by configuring the Surefire plugin. But there is some technical reason for this behavior?

Thanks in advance

Roberto

[Evgeny Mandrikov]

Hi,

Initially in version 0.6.1 this was implemented as prepending of empty string ( see https://github.com/jacoco/jacoco/commit/ca863838a09a935572c3291da708870f6b9bc3c3#diff-1e1f9f25011241fca234b2856ec18b8eR175 associated with https://github.com/jacoco/jacoco/issues/44 ) to cover scenario when execution is skipped with following configuration

<properties>

  <-- no argLine here -->

</properties>

<plugin>

  <groupId>org.apache.maven.plugins</groupId>

  <artifactId>maven-surefire-plugin</artifactId>

  <configuration>

    <argLine>-foobar ${argLine}</argLine>

  </configuration>

</plugin>

According to https://github.com/jacoco/jacoco/pull/192 there was regression in 0.6.4 regarding this.

But unfortunately behavior wasn't fully restored in 0.6.5 ( https://github.com/jacoco/jacoco/commit/c4aef33c74400419852d76b6579fbcbf58b4666e ) , i.e. it started to set empty instead of prepending empty string.

All in all - thank you for finding this bug! I created ticket https://github.com/jacoco/jacoco/issues/486

For now there are seems to be multiple ways to workaround this, like the one that you mention. Another one - is to use property dedicated for JaCoCo using "propertyName" parameter ( http://www.jacoco.org/jacoco/trunk/doc/prepare-agent-mojo.html#propertyName ).

Hope this helps.

Regards,

Evgeny

[Roberto Andrioli]

Now everything makes sense :)

Nice tip about the "propertyName".  I can append this property manually in the argLine property and don't need to configure the Surefire plugin. Great.

I'll change my code to use that until next version

Thanks

Roberto

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