Start work on the maven plugin

[gaganis]

Hello All,

I was thinking on starting work for the maven plugin, so this issue is to ask whether anyone has already started to work, and to act as a placeholder for related discussion.

Thanks
Giorgos

[jbduncan]

Hi @gaganis, I haven't done any work towards the Maven plugin myself, but I don't know about @nedtwigg...

[nedtwigg]

The maven plugin is completely greenfield. It's all yours :)

[jbduncan]

@gaganis Do you have any initial work that you can share with us, or has this fallen off your radar?

[gaganis]

@jbduncan Unfortunately I have nothing working to share. I tried starting with building a hello world maven plugin in the gradle build of spotless but despite putting quite an effort I was unable to make it work.

I tried using https://dev.liferay.com/develop/reference/-/knowledge_base/7-0/maven-plugin-builder-gradle-plugin and also using mavenEmbedder directly but I got stuck which is why I did no progress.

My latest non-working attempt was using the following maven-plugin build.gradle file:
https://gist.github.com/gaganis/fb0a8d1e27bbaf61281b9314a62bd95b

This is definitely still on my radar and I am planning to give it another try.

Any help on building the plugin would be very welcome 😄

[jbduncan]

May I suggest applying maven-plugin-builder-gradle-plugin to a brand-new Gradle Java project, where its only Java source file is a "Hello World" Mojo (as described near the start of https://maven.apache.org/guides/plugin/guide-java-plugin-development.html)?

If you can get your head around that, then you may be able to gradually build up the build.gradle in this brand-new project so it looks more like Spotless's, and then track down what's causing you problems.

[gaganis]

Thank you for the feedback @jbduncan 😄 I will try your suggestion.

[jbduncan]

You're welcome @gaganis. I'm sorry that I can't provide any easier-to-follow or more specific advice in this situation. I wish you best of luck with these endeavours. :)

[leonard84]

An alternative would be to use maven directly, with maven-wrapper and a pom.xml. The reason for that being that maven has great support for generating its plugins, e.g. maven-invoker integration tests and so on.

[jbduncan]

@leonard84 That could be done, but it would mean that we couldn't share Gradle build script settings in build.gradle and gradle/*.gradle with the pom.xml, which would introduce build logic duplication, I suspect.

[nedtwigg]

We're happy to take whatever is easiest - duplicating build logic in maven might be easier than reinventing maven's plugin development in gradle. Author's choice :)

[leonard84]

Spring Boot does it the other way round (building gradle-plugin within a maven project) https://github.com/spring-projects/spring-boot/tree/master/spring-boot-tools. You basically need to write an adapter build.gradle file that calls maven.

[jbduncan]

@leonard84 That sounds like a neat idea IMO. (Having viewed how Spring Boot does it with Maven-to-Gradle, it seems perfectly doable the other way around.)

In that case, I'm happy regardless of whether the Maven plugin is managed with Gradle or Maven, since we can eventually tie everything with Gradle if needed (as future work). :)

[leonard84]

@jbduncan I created a small proof of concept here https://github.com/leonard84/spotless/tree/mvn-plugin
It works by using a templated pom.xml and injects the gradle.properties, then it uses the maven-wrapper in an exec task to execute the maven build.

What still needs to be done:

• configure the maven plugins
• figure out a way to use the spotless lib from the current project build
  • one way would be to depend on the install task of the lib to use the local maven repository
  • currently it just depends on the stable version
• write the actual plugin
• add mvn-invoker integration tests

[jbduncan]

Looks good so far @leonard84! I just have a couple of comments (1, 2) about the current implementation, but other than that, it looks like a good starting point.

But first of all, if you're intending continue, then I'd encourage you to wait a bit, as I believe @gaganis is still working on this himself.

@gaganis, do you find @leonard84's contribution so far helpful for your own efforts? Would you be happy if @leonard84 continues down his own avenue, on the understanding that he may tread on your toes? Overall, is this issue something that you still want to work on?