Maven cannot find JRuby mojo descriptors

Question

I followed the instructions to the letter in this blog post by Sonatype on writing a Maven plugin in Ruby.

When I try running mvn install (Maven 3.0.4), the build is successful, but maven-plugin-plugin cannot find any mojo descriptors:

[INFO] ------------------------------------------------------------------------
[INFO] Building Example Ruby Mojo - firstruby-maven-plugin 1.0-SNAPSHOT
[INFO] ------------------------------------------------------------------------
[WARNING] The POM for org.jruby:jruby:jar:0.9.9 is invalid, transitive dependencies (if any) will not be available, enable debug logging for more details
[INFO]
[INFO] --- maven-plugin-plugin:2.4:descriptor (default-descriptor) @ firstruby-maven-plugin ---
[INFO] Using 3 extractors.
[INFO] Applying extractor for language: java
[INFO] Extractor for language: java found 0 mojo descriptors.
[INFO] Applying extractor for language: jruby
[INFO] Extractor for language: jruby found 0 mojo descriptors.
[INFO] Applying extractor for language: bsh
[INFO] Extractor for language: bsh found 0 mojo descriptors.

If I try bumping maven-plugin-plugin version to anything higher than 2.4, the build fails with this error message:

[ERROR] Failed to execute goal org.apache.maven.plugins:maven-plugin-plugin:2.5:descriptor (default-descriptor) on project firstruby-maven-plugin: The API of the mojo scanner is not compatible with this plugin version. Please check the plugin dependencies configured in the POM and ensure the versions match. org.apache.maven.tools.plugin.scanner.MojoScanner.populatePluginDescriptor(Lorg/apache/maven/tools/plugin/PluginToolsRequest;)V -> [Help 1]

Here's the output of tree to show that the directory structure is OK:

firstruby-maven-plugin
├── pom.xml
└── src
    └── main
        └── scripts
            └── echo.rb

3 directories, 2 files

Any idea why it's not working?

Answer 1

The Codehaus jruby-maven-plugin seems to have been abandoned 5 years ago. If you're using Maven3, you can try using Maven2 but I'd look at https://github.com/torquebox/jruby-maven-plugins