Make Checkstyle an (automatic) module

[future2r]

Checkstyle 10.x requires JDK 11 to run. Wouldn't it be the right time to finally make it a Java module (introduced with JDK 9)?

I have implemented some Checks for Checkstyle by my own. My project complains about an 'unstable module name derived from the file name'. Even Maven warns about not uploading my project to a public repository, since the build is far from being stable.

Since the filename is something like checkstyle-10.12.6.jar, Java ends up with the module name checkstyle. Usually, a good naming would be the name of the main package, in this case com.puppycrawl.tools.checkstyle. This is more expressive and more unique.

You may achieve this just by adding a module-info.java into your source root. For the beginning you may export all your packages and open those, that require reflection.

If this is not an option, please add AutomaticModuleName to the MANIFEST.MF. In this case, at least the module name is no longer constructed from the file name.

https://dzone.com/articles/automatic-module-name-calling-all-java-library-maintainers

jlink requires module-info.java, see details at #14666

[romani]

Even Maven warns about not uploading my project to a public repository, since the build is far from being stable.

Please share details. We use maven for long time, never had a problem.

Since the filename is something like checkstyle-10.12.6.jar

I thought all maven artifacts are named like this, org name is in path/folders of maven repository. Please share details/examples that some other old projects are migrating.

Usually, a good naming would be the name of the main package, in this case com.puppycrawl.tools.checkstyle

Did you miss version and extension?

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Please share link to your project with extension of checkstyle

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What benefits our project will have from this?
What benefits our users will have? What problems they have now?

We have two plugins in our org ( sonar and eclipses), how it will help them?

Is it somehow breaking compatibility issue for some users? To let us plan it accordingly.

[future2r]

It is not about Maven, it is about the Java 9 module system.

This is the module-info.java of the project with my implemented checks:

module com.qualitype.modaplex.checkstyle {

    requires java.xml;
    requires transitive checkstyle;

    exports com.qualitype.modaplex.checkstyle;
}

Java Compiler (since Java 9):
"Name of automatic module 'checkstyle' is unstable, it is derived from the module's file name."

Maven:
"[WARNING] Required filename-based automodules detected: [checkstyle-10.12.6.jar]. Please don't publish this project to a public artifact repository!"

Please check this for more background: https://dzone.com/articles/automatic-module-name-calling-all-java-library-maintainers

[romani]

I am not sure I can find time to investigate all of this.
Can you contribute module definition to us ?
Maybe by example and initial implementation we will be onboarder quicker. I will invite plugin maintainers to double check that we will not affect them.

[future2r]

Sure, I can try.

For the beginning, the simplest way would be to make Checkstyle a named automatic module. All you need to do is, add this line to your MANIFEST.MF:

AutomaticModuleName=com.puppycrawl.tools.checkstyle

This should change nothing in the behavior when used in a non-modularized environment. However, when used in a modularized environment, all those warnings should disappear.

Depending on your project setup this can be done manually or as a configuration in the packaging in the pom.xml. It will try this in a branch and let you know about the result.

The next step would be to create a proper module-info.java. This may be a bit harder, depending on how much of your code is considered as a public API and how much reflection is used. Furthermore, it depends on the state of modularization of your dependencies. I will try this in another branch,

This will be my first contribution to an open source project. So please be patient with me.

Best regards,
Frank

[future2r]

I did my very best. Hope this will help you. #14139

[rnveach]

@future2r When working on the backport release ( rnveach/checkstyle-backport-jre8#13 ), I received the following error:

Caused by: org.apache.maven.plugin.MojoExecutionException: Error assembling JAR
	at org.apache.maven.plugins.jar.AbstractJarMojo.createArchive(AbstractJarMojo.java:281)
	at org.apache.maven.plugins.jar.AbstractJarMojo.execute(AbstractJarMojo.java:305)
	at org.apache.maven.plugin.DefaultBuildPluginManager.executeMojo(DefaultBuildPluginManager.java:126)
	at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute2(MojoExecutor.java:342)
	... 25 more
Caused by: org.codehaus.plexus.archiver.jar.ManifestException: Invalid automatic module name: 'com.puppycrawl.tools.checkstyle-backport-jre8'
	at org.apache.maven.archiver.MavenArchiver.createArchive(MavenArchiver.java:702)
	at org.apache.maven.plugins.jar.AbstractJarMojo.createArchive(AbstractJarMojo.java:274)
	... 28 more

When I run verify test -e with PMD/Jacoco skips, the job seems to work fine. However, when I run the same command with skipping tests, I then get the above failure. This does not happen with the same commands in the main repo. Reverting 8ac4fcd fixes the run in backport.

Do you happen to know why this is? Is this because this project is for Java 8 only and this automatic module is more Java 9+?

Edit: I see now. It is because the artifact name has -. When I switch them to _, it resolves the issue. It is odd that it only occurs when skipping tests though.