No Java classes available in tycho project within eclipse

[moley]

Hi to all,

I have a tycho build, which is working in commandline (means mvn verify, mvn install and mvn eclipse:eclipse works like a charme).
As soon as I import the project via "Import - Existing mavenproject" (after .project and .classpath files are removed) into eclipse (2022-09, Build id: 20220908-1902) on mac it seems that eclipse does not detect any sourcefolder. No classes can be resolved. As well no JDT builder is configured. As soon as I configure Java Nature manually JDT builder is triggered, but I recieve many build errors (e.g. package seems to be not correct although in Java Build Path properties folder "src" is detected correctly as source folder. Can you please help me? What's the default way of opening a tycho build inside eclipse?

[jcompagner]

Can I ask, why do you remove .project and .classpath. The 2 files that have this info/configuration for eclipse?

[moley]

Coming from idea and gradle I thought this is the way to go. Because in this scenario buildship plugin recreates the files. So is the right way here to create .project and .classpath with mvn and import as mvn project as second step?

[mickaelistria]

Tycho projects are usually Eclipse PDE projects first, and most of PDE metadata is stored in .project and .classpath. Tycho is MANIFEST-first, you'd rather actually keep the .project and .classpath and use Tycho pom-less which is capable of dynamically generating the pom files (so you don't have to store them in your Git repo).
The Eclipse-first approach works more easily than the Maven-first approach for PDE projects, both in the IDE and in Tycho.

[laeubi]

Project files itself are not that essential but .classpath often is because the JDT(!) default is to use different layout than maven and most of the time this is not reflected in the pom configuration.... I think I already created a bug for this but is lost somehwere at all the platform repositories (can't find it anymore)

[moley]

Ok, thanks for all the feedback. I will try it out. Maybe a user documentation at a prominent place would be nice? Or - if yet available - a link in the github README.md. If available and I didn't see, then sorry about me

[HannesWell]

What has been said is all correct, but I want to add that recently the previously separate Tycho-Connector was migrated to M2E

• Add project configurator for tycho packagings eclipse-m2e/m2e-core#967

TLDR; unless your project requires special .classpath files, M2E (the Maven integration of Eclipse) should generate all the mentioned files for Tycho Maven projects as well with the upcoming release (will probably be part of Eclipse 2022-12).

If you are interested you can try out the latest M2E 2.1.0 snapshot at:
https://download.eclipse.org/technology/m2e/snapshots/2.1.0/

If there is something missing and you think it is a general issue, please open a dedicated issue at Eclipse M2E and consider to contribute a corresponding patch. :)

[lppedd]

Imho one of the problems of Eclipse is that it hides Maven. You tend to forget about it with all the autoconfiguration. Also some parts of Tycho extract info from Eclipse-first configuration files, but that isn't obvious.

I prefer to work directly with Maven and that's why it has been a mission for me to get IDEA working with Tycho customizations.

[lppedd]

@laeubi

if there is no interest in it

Every OS initiative starts on the 90-9-1 model, where only the 1% do something. When the engagement start going up, contributors start arriving too. The fact PDE is not being addressed in other tools is probably more of a political thing from every perspective:

1. Eclipse does not try to push for it
2. Not many users in other IDEs as it's frustrating/impossible
3. IDE makers have no interest because the userbase is too small

This is a infinite loop unfortunately.

there is too much work for too less developers

That's perfectly understandable and I'm not here to ask for full support in IJ. On the Tycho side it's just an added cool thing to remember about other IDEs during development. E.g. if someday you decide to support only POM-less, IJ users are definitely screwed.

Contribute your self

Yeah that's what I did, there is an open PR for Tycho support in IJ on the community repository

[jcompagner]

isn't tycho really a build tool to build eclipse based or also maybe "osgi" based applications?

You seem to want to manage dependencies with mvn for osgi based stuff?

I would really hate that i need to also specify my eclipse projects/plugins also in mvn, thats not where i say where it depends on
thats all in the manifest.. (package imports, or bundle imports)

The system (and thats what tycho really does when building command line) is setting up all the dependencies based on target platform (and i think that target platform can be configured more and more to come from pure mvn central artifacts, as long as they are correct osgi bundles)

But you seem to be thinking this as pure java projects with dependencies that are coming from somewhere like a pom.xml file..

I am not sure what you are building, but if you are building a Eclipse based application then there you just have to use tycho to build it fully so that you fuse mvn and osgi together.
But if you are just building an (web)application and you are not really building a eclipse based application you shouldn't use tycho at all.. then you can just just use "pure" mvn.

[HannesWell]

If you want to build OSGi applications in a pom/maven first approach you also may want to consider to use the bnd-maven-plugin to only generate you manifest.

• https://mvnrepository.com/artifact/biz.aQute.bnd/bnd-maven-plugin
• https://github.com/bndtools/bnd/tree/master/maven/bnd-maven-plugin

Your desire to have a pom/maven first and only build is totally valid and I agree that this is a way that is more cross-IDE compatible.
Nevertheless to goal of Tycho is actually to fully support and leverage the META-INF/MANIFEST.MF-first approach used/introduced by Eclipse PDE. And at least my goal when it comes to Tycho is actually always to reduce the number of pom-files as far as possible and let Tycho derive as much as possible from the other PDE files in order to avoid duplication of information.

If you have suggestions for certain improvements please don't hesitate to mention them, but steering Tycho towards using more poms will likely not happen because it contradicts the goal of Tycho to be a 'Manifest-first' build tool.
Nevertheless you are still not forced to use Tycho without poms. And in Tycho 2.7.5 there even has been a generate-poms mojo:
https://tycho.eclipseprojects.io/doc/2.7.5/tycho-pomgenerator-plugin/generate-poms-mojo.html

[lppedd]

@HannesWell thanks for the suggestion. I had starred that plugin some time ago while I was evaluating possible approaches in keeping the IDE-related metadata at a minimum. To be honest in the OSGi ecosystem there is currently nothing comparable to what Tycho offers, and that's why I'm still very comfortable with using it. Otherwise I would not have opened a PR or I would not be following issues/PRs daily.

reduce the number of pom-files as far as possible

This is a something I perfectly understand when looking at it from an Eclipse-first development experience. However I do hope the time of pom-less-only never arrives, or at least not before the tooling in the PDE ecosystem has improved.

It's not really that I want a pure Maven solution, it's more that Tycho and PDE are developed in parallel because of obvious reasons, and other development environments do not get the necessary attention. In the past six months I was able to reduce the interactions with Eclipse as far as not having to open it to launch the application. I got Tycho to load correctly in IntelliJ IDEA, but the hours I've spent on these points are just surreal.

steering Tycho towards using more poms

No no, to clarify, I don't want it to use more POMs, just the POMs required by the Maven standard. If Tycho contributes to the Maven model with properties, dependencies, and whatsoever, keeping it as standard as possible then refactoring IDE Maven integrations to fully cover what Tycho does is possible.

Some people here see Maven as only a build tool, but it is extremely important for other IDEs as they can actually allow coding without understanding what OSGi/PDE is, they just need to know about Maven.

[laeubi]

No no, to clarify, I don't want it to use more POMs, just the POMs required by the Maven standard. If Tycho contributes to the Maven model with properties, dependencies, and whatsoever, keeping it as standard as possible then refactoring IDE Maven integrations to fully cover what Tycho does is possible.

Some people here see Maven as only a build tool, but it is extremely important for other IDEs as they can actually allow coding without understanding what OSGi/PDE is, they just need to know about Maven.

I think there is a general misunderstanding here, pomless build do not mean there is no pom nor that it is not "maven standard", it is based on polyglot-extension and every "maven aware ide" should be able to support this.

[laeubi]

@moley I think we have diverged a bit from the original topic. For your particular case, if you think things can be improved it would be best to share an example that reproduces the problem and head over to m2eclipse what actually do the maven > eclipse conversion here.

[moley]

Yes, sorry for starting this discussion. Didn't want to blame or grumble.
So meanwhile I am step ahead.... Projects are imported and src folders are used. I have another problem recieving "Project is missing required Java Project" although compilable at commandline, I can head over to m2eclipse for this case. Thanks for leading me to the right direction 👍