[question] why are some plugins bound to the package phase executed by eclipse lifecycle mapping by default and others not?

[reto-hoehener]

In Eclipse 2024-06, new workspace, when I create a simple maven project with 2 plugins bound to the package phase, one is ignored and one is executed.

I thought Eclipse only considers phases up to and including compile as 'interesting', but I couldn't find any documentation about this, only hints here: https://eclipse.dev/m2e/documentation/m2e-execution-not-covered.html

I had a look inside the maven-dependency-plugin jar but did not observe any META-INF/m2e lifecycle mapping that could explain the execution. I clearly observe the junit dependency being copied to target/dependency by the Eclipse workspace build (no manual maven execution).

Is the maven-dependency-plugin treated special by m2e?

<project xmlns="http://maven.apache.org/POM/4.0.0"
  xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
  xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd">
  <modelVersion>4.0.0</modelVersion>

  <groupId>test</groupId>
  <artifactId>test</artifactId>
  <version>1.0.0</version>
  <packaging>jar</packaging>

  <properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
  </properties>

  <build>
    <plugins>
      <plugin>

        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-antrun-plugin</artifactId>
        <version>3.1.0</version>
        <executions>
          <execution>
            <id>id</id>
            <phase>package</phase>
            <goals>
              <goal>run</goal>
            </goals>
            <configuration>
              <target>
                <echo>Hello world!</echo>
              </target>
            </configuration>
          </execution>
        </executions>
      </plugin>

      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-dependency-plugin</artifactId>
        <version>3.7.1</version>
        <executions>
          <execution>
            <id>id</id>
            <phase>package</phase>
            <goals>
              <goal>copy</goal>
            </goals>
          </execution>
        </executions>
        <configuration>
          <artifactItems>
            <artifact>
              <groupId>junit</groupId>
              <artifactId>junit</artifactId>
              <version>4.11</version>
            </artifact>
          </artifactItems>
        </configuration>
      </plugin>

    </plugins>
  </build>
</project>

[laeubi]

In your screenshot you can see that the antrun plugin is ignored (I assume it has a mapping for that), the dependency plugin is executed because mojos are executed by default if not otherwise specified.

[reto-hoehener]

@laeubi are you sure? that is the core of my question: I thought only plugins bound to "interesting phases" (i.e. up to compile) are executed by eclipse? at least that's what is written in the linked page.

[laeubi]

See https://github.com/eclipse-m2e/m2e-core/blob/master/RELEASE_NOTES.md#mojos-without-a-mapping-are-now-executed-by-default-in-incremental-builds

[reto-hoehener]

Thanks for that pointer, that's good to know. So the package phase is an "interesting" phase for m2e? I mean, plugins bound to test/install/deploy are surely never executed by m2e, right?

I will check the maven-antrun-plugin...

[reto-hoehener]

In your screenshot you can see that the antrun plugin is ignored (I assume it has a mapping for that), the dependency plugin is executed because mojos are executed by default if not otherwise specified.

I checked the plugin jar and don't see a META-INF/m2e folder. Are there other ways to specify m2e mappings that I can check?

[laeubi]

m2e ship with some default mappings ifecycle-mapping-metadata.xml and as far as I know every phase can be interesting. The question is more do you want the antrun to execute (than you can enable it e.g with processing instructions (I can't find the n&n at the moment maybe @HannesWell knows them?) or if you like to disable the maven-dependency-plugin?

[reto-hoehener]

I am mainly trying to update my mental model of how m2e is supposed to work with relation to the package phase: I was surprised by the maven-dependency-plugin being executed, because I thought m2e would never automatically execute plugins bound to the package phase. Now you pointed me to the release notes that say that m2e executes all plugins by default, which I think is not the case at least for the test/install/deploy-phases. I believe my custom plugins bound to the package phase are also not executed by default but I have to recheck those.

I tried to click on "Open workspace lifecycle mappings metadata" but got an error message and an empty editor. Edit: Now it works (but this mapping is empty).

[laeubi]

Yes it is not always easy when it comes to mappings, but you can open the LifeCycle Mappings as a view to at least get the info what is executed.

In this particular case I think the reason is that m2e has a default mapping for maven-dependency-plugin here that is used when nothing else is configured.

So even if the package-phase is "uninteresting" by default, if there is a mapping (either implicit or explicit) m2e can execute mojos in such a phase.

So here we have:

1. maven-antrun-plugin:run has no explicit or implicit binding and package phase is uninteresting -> ignored
2. maven-dependency-plugin:copy-dependency has implicit default binding -> execute regardless of phase.