Add packagingTypes extension point

[kjsmita6]

Our application has a few custom Maven packaging types that do not show up in the drop-down and must be typed in manually in the pom.xml. This small change adds an extension point that allows the developers of the product/plugins to define packaging types that will be added to the pom editor.

The extension point is defined by the following:

which will add a packaging type test-packaging-type. This type does not actually exist and is only here for testing, which is why the next screenshot shows an error. The plugin developers should make sure that the packaging type actually will exist in the launched product.

Then, in the launched product, see the type in the pom editor drop-down.

This is my first contribution to any Eclipse project, so please let me know if I did something incorrectly.

[mickaelistria]

Thanks, we'll try to look at it shortly. We first need a positive review from CI to validate this change doesn't introduce regressions.

[laeubi]

I think this is another reincarnation of missing extension support in m2e as packaging types are normally declared via a plugin in the pom already.

[mickaelistria]

I think this is another reincarnation of missing extension support in m2e as packaging types are normally declared via a plugin in the pom already.

That's right!
So I don't think we want a new extension point for that, if this information is supposed to be accessible dynamically from the Maven project.

[mickaelistria]

Sorry @kjsmita6 but as @laeubi identified, this proposal is not really correct nor sufficient for m2e. We can achieve much better results by looking up build extensions (that's not trivial though, as #118 tracks). So I think we're going to close this PR.
However you may want to create a new PR adding a comment in the Overview page to remind that with extension support, it would be possible to dynamically list all packaging types that make sense for the current project.

[laeubi]

(that's not trivial though, as #118 tracks

That said, we already have some workarounds for packaging types in place in m2e, maybe this could simply be reused her, take a look at:

m2e-core/org.eclipse.m2e.core/src/org/eclipse/m2e/core/internal/project/registry/DefaultMavenDependencyResolver.java

Lines 98 to 105 in 840fb2e

	// extension plugins (affect packaging type calculation)
	for(Plugin plugin : mavenProject.getBuildPlugins()) {
	if(plugin.isExtensions()) {
	ArtifactKey artifactKey = new ArtifactKey(plugin.getGroupId(), plugin.getArtifactId(), plugin.getVersion(),
	null);
	requirements.add(MavenRequiredCapability.createMavenArtifact(artifactKey, "plugin", false)); //$NON-NLS-1$
	}
	}

one could the parse these plugins for components.xml descriptors declaring new packaging types (thats how maven seems to handle them).

[mickaelistria]

That would be very good and it may open some first breaches towards tackling #118.
@kjsmita6 are you interested in implementing the approach suggest by @laeubi , introspecting the project plugins for declared packaging types?

[kjsmita6]

@mickaelistria I could be interested in working on this, as it's something we need in our product. I will investigate some things, try and implement them, and create another PR when necessary.

[mickaelistria]

@kjsmita6 Thanks! And feel free to ping on issues or on the m2e-dev mailing-list if you need any assistance.

[laeubi]

And feel free to ping on issues or on -the m2e-dev mailing-list- if you need any assistance.

Better use the https://github.com/eclipse-m2e/m2e-core/discussions