[MPLUGIN-321] improve documentation on maven-plugin-annotations telling that optional=true is sufficient

• Type: Improvement
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Affects Version/s: 3.5
• Fix Version/s: 3.5.1
• Component/s: maven-plugin-annotations
• Assignee: Robert Scholte
• Reporter: Herve Boutemy
• Created: 23/Dec/16 07:13
• Updated: 15/Jan/17 14:06
• Resolved: 15/Jan/17 13:22

Description

https://maven.apache.org/plugin-tools-archives/plugin-tools-3.5/maven-plugin-plugin/examples/using-annotations.html#POM_configuration
tells

  <dependencies>
    <!-- dependencies to annotations -->
    <dependency>
      <groupId>org.apache.maven.plugin-tools</groupId>
      <artifactId>maven-plugin-annotations</artifactId>
      <version>3.5</version>
      <scope>provided</scope><!-- annotations are needed only to build the plugin -->
    </dependency>
  </dependencies>

Yes, annotations are needed only to build the plugin, since they have @Retention(value=CLASS) which means they stay in bytecode but are not loaded at runtime.
What is not clear is that this dependency is not really provided at runtime: Maven core does not inject maven-plugin-annotations at runtime (why would it? Maven core works by reading META-INF/maven/plugin.xml). But the dependency is simply not used at runtime.

This doc can be improved:

<!-- annotations are not used at runtime because @Retention(value=CLASS), they are needed only to build the plugin -->

Issue Links

• relates to: MNG-6135 Maven plugins and core extensions are not dependencies, they should be resolved the same way as projects.
• relates to: MRESOLVER-8 ScopeDependencySelector incorrectly de-selects direct dependencies
• relates to: MPLUGIN-296 java.lang.ClassNotFoundException: org.apache.maven.plugins.annotations.Execute