Add mojo to custom lifecycle defined by another maven plugin

Question

I'm using a maven plugin that defines a custom packaging type and lifecycle for my projects. Lets call this packaging "foo", defined by the "foo-plugin". I have no control over said plugin, but I want to extend it's lifecycle definition in my plugin.

I am writing another plugin, lets call this one the "bar-plugin". I want a certain goal of my plugin to be invoked in the process-sources phase of a project with "foo" packaging. Not in any other case. I have defined a mojo to execute in the process-sources phase but this makes it execute in the process-sources phase of any project, not just those with packaging "foo".

/**
 * @goal bar
 * @phase process-sources
 */
public class BarMojo extends AbstractMojo

I have also tried to use a custom lifecycle definition to extend the existing lifecycle, like this:

<component-set>
  <components>
    <component>
      <role>org.apache.maven.lifecycle.mapping.LifecycleMapping</role>
      <role-hint>foo</role-hint>
      <implementation>org.apache.maven.lifecycle.mapping.DefaultLifecycleMapping</implementation>
      <configuration>
        <phases>
          <process-sources>${groupId}:${artifactId}:${version}:bar</process-sources>
        </phases>
      </configuration>
    </component>
  </components>
</component-set>

This seemed to be totally ignored, even with the <extensions> element in the pom set to true. Is it even possible to extend a lifecycle defined by one plugin using another plugin and if so, what am I doing wrong?

Edit: The maven project structure is as follows: project-name (packaging)
mycompany-parent (pom)
- someprojecttype-parent (pom)
- - project-1 (foo)
- - project-2 (foo)

I want to add the plugin to someprojecttype-parent, which has packaging set to pom. This causes the bar goal to execute while building the parent project. I only want to execute the bar goal when building project-1 and project-2.

Answer 1

judging from the last bit it sounds like you need to put the plugin inside

<build>
    <pluginManagement>
        <plugins>

rather than just

<build>
    <plugins>

that should restrict execution to the child projects