maven plugin execution

Question

When will plugin execute if I don't specify a phase?

for example that plugin

<plugin>
    <groupId>com.vaadin</groupId>
    <artifactId>vaadin-maven-plugin</artifactId>
    <version>1.0.1</version>
    <executions>
      <execution>
        <configuration>
          <!-- if you don't specify any modules, the plugin will find them -->
          <!-- <modules> <module>learning.vaadin.gwt.ColorPickerWidgetSet</module> </modules> -->
        </configuration>
        <goals>
          <goal>update-widgetset</goal>
        </goals>
      </execution>
    </executions>
  </plugin>

Answer 1

It depends on the plugin. If the plugin author specified an @phase in the mojo metadata, it will end up there. If not, it won't run at all.