As of 3.2.18/3.3.6/3.4.0, optional dependencies won't be published in pom.xml anymore

[simonbasle]

Motivation

While originally a side effect of removing problematic dependency plugin (see #2151), we discussed this with the team and took some insight from the Spring Framework and Spring Boot teams and decided that we'd stop publishing optional dependencies to the pom.

For now we won't advertise a feature in Gradle either. Note the only candidate would be metrics (with the optional dependency to micrometer).

For more context, see spring-projects/spring-framework#23234

Desired solution

The optional entries are effectively already out of the pom. The MavenPublication.withXml() is currently no-op, and should be replaced with a comment pointing to this issue for context.

Considered alternatives

If we were to re-introduce optional-marked dependencies in the generated Maven pom, the following block of code should be used in MavenPublication.withXml() in the Gradle build:

withXml {
	project.configurations.optional.allDependencies.each { optDep ->
		Node d = asNode().dependencies[0].appendNode('dependency')
		d.appendNode('groupId', optDep.group)
		d.appendNode('artifactId', optDep.name)
		d.appendNode('version', optDep.version)
		d.appendNode('scope', 'compile')
		d.appendNode('optional', true)
		println "$optDep.group:$optDep.name:$optDep.version has been marked as optional in generated pom"
	}

	//groovy magic incantation to sort dependencies alphabetically (optional/scope/group/name..)
	def sorted = asNode().dependencies[0].children().collect().sort { it.optional.text() + it.scope.text() + it.groupId.text() + it.artifactId.text() }
	asNode().dependencies[0].children().with { deps ->
		deps.clear()
		sorted.each { deps.add(it) }
	}
}