Custom Maven packaging, transitive dependencies aren't included

Question

I'm playing around with a custom Maven 3 packaging plugin for some non-java artifacts, and having an issue getting transitive dependencies to work. I've got three projects defined, model, model-impl, and cli, with dependencies like this:

cli
  model-impl
    model

My custom lifecycle plugins are being called in each project, and I can successfully build model and model-impl. For each of those projects, the expected artifacts are being stored in my local repository. cli however is failing because I don't get model as a dependency in my Mojo. I'm not completely sure that this is a problem in my code though, because even using mvn dependency:dependency-tree doesn't show the full dependency hierarchy:

[INFO] Scanning for projects...
[INFO]
[INFO] ----------------------< com.corp.nodes:myproj-cli >-----------------------
[INFO] Building myproj Test 1.0.0-SNAPSHOT
[INFO] --------------------------------[ myproj ]--------------------------------
[INFO]
[INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ myproj-cli ---
[INFO] com.corp.nodes:myproj-cli:myproj:1.0.0-SNAPSHOT
[INFO] \- com.corp.:myproj-model-impl:myproj:1.0.0-SNAPSHOT:compile
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------

Here I would have expected that I see a tree with three levels for each of the projects.

Here's the components.xml defined in my custom plugin:

<component-set>
    <components>
        <component>
            <role>org.apache.maven.lifecycle.mapping.LifecycleMapping</role>
            <role-hint>myproj</role-hint>
            <implementation>
                org.apache.maven.lifecycle.mapping.DefaultLifecycleMapping
            </implementation>
            <configuration>
                <phases>
                    <initialize>com.corp.maven:myproj-plugin:unpackageDependencies</initialize>
                    <process-resources>org.apache.maven.plugins:maven-resources-plugin:resources</process-resources>
                    <compile>com.corp.maven:myproj-plugin:compile</compile>
                    <process-test-resources>org.apache.maven.plugins:maven-resources-plugin:testResources</process-test-resources>
                    <test-compile>org.apache.maven.plugins:maven-compiler-plugin:testCompile</test-compile>
                    <test>org.apache.maven.plugins:maven-surefire-plugin:test</test>
                    <package>com.corp.maven:myproj-plugin:package</package>
                    <install>org.apache.maven.plugins:maven-install-plugin:install</install>
                    <deploy>org.apache.maven.plugins:maven-deploy-plugin:deploy</deploy>
                </phases>
            </configuration>
        </component>
        <component>
            <role>org.apache.maven.artifact.handler.ArtifactHandler</role>
            <role-hint>myproj</role-hint>
            <implementation>org.apache.maven.artifact.handler.DefaultArtifactHandler</implementation>
            <configuration>
                <type>myproj</type>
                <extension>myproj</extension>
                <packaging>myproj</packaging>
                <addedToClasspath>true</addedToClasspath>
                <includesDependencies>true</includesDependencies>
            </configuration>
        </component>
    </components>
</component-set>

All of the project POMs have their packaging set to myproj, and all of the dependencies have their type set to myproj. Here's the pom for the cli project:

<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 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.corp.arthur.nodes</groupId>
    <artifactId>myproj-cli</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <packaging>myproj</packaging>

    <name>myproj Test</name>

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

    <dependencies>
        <dependency>
            <groupId>com.corp.arthur</groupId>
            <artifactId>myproj-model-impl</artifactId>
            <version>1.0.0-SNAPSHOT</version>
            <type>myproj</type>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>com.corp.maven</groupId>
                <artifactId>myproj-plugin</artifactId>
                <version>1.0.0-SNAPSHOT</version>
                <extensions>true</extensions>
            </plugin>
        </plugins>
    </build>
</project>

The POM for the impl project looks similar. Any idea's what I'm missing?

Answer 1

Finally figured out what was going on by tracing through the source for the DefaultDependencyCollector class. Turns out I needed to set includesDependencies in my components.xml to false. What was happening is the dependency collector saw that flag was true, meaning the dependencies were included in the artifact, and so didn't recurse through them. With it set to false, it does recurse, and I get the expected behavior.

[INFO] Scanning for projects...
[INFO]
[INFO] ------------------< com.corp.nodes:myproj-cli >------------------
[INFO] Building myproj Test: CLI Node 1.0.0-SNAPSHOT
[INFO] --------------------------------[ myproj ]--------------------------------
[INFO]
[INFO] --- maven-dependency-plugin:2.8:tree (default-cli) @ myproj-cli ---
[INFO] com.corp.nodes:myproj-cli:myproj:1.0.0-SNAPSHOT
[INFO] \- com.corp:myproj-model-impl:myproj:1.0.0-SNAPSHOT:compile
[INFO]    \- com.corp:myproj-model:myproj:1.0.0-SNAPSHOT:compile
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------

Answer 2

I've been struggling with a similar problem while trying to include my android lib via maven to my another project. My research has shown that library's pom file isn't included in maven library for some cases like mine was - I had an .aar file. Hence, your project build system doesn't know anything about these transitive dependencies. The solution for me was to manually point them in in my Gradle file. You can familiarize with this more concretely in this topic.