Why can't gradle find my local maven dependency with a classifier?

Question

I have a package which is a JNI wrapper around native code and is therefore platform dependent. I want to create a platform specific jar using os-maven-plugin. The relevant part of my pom is as follows:

<groupId>foo.bar.baz</groupId>
<artifactId>project</artifactId>
<version>0.0.1-SNAPSHOT</version>
<packaging>jar</packaging>


<build>
    <extensions>
        <extension>
            <groupId>kr.motd.maven</groupId>
            <artifactId>os-maven-plugin</artifactId>
            <version>1.6.1</version>
        </extension>
    </extensions>
    <plugins>
        <plugin>
           <artifactId>maven-jar-plugin</artifactId>
           <version>3.1.0</version>
           <configuration>
                <classifier>${os.detected.classifier}</classifier>
            </configuration>
        </plugin>
    </plugins>
    // ...

After running mvn clean install, it seems the artifact is built appropriately:

$ ls /Users/erip/.m2/repository/foo/bar/baz/project/0.0.1-SNAPSHOT
_remote.repositories                        project-0.0.1-SNAPSHOT-osx-x86_64.jar
maven-metadata-local.xml                    project-0.0.1-SNAPSHOT.pom

however, when I add this dependency to my gradle file…

repositories {
    // ...
    mavenLocal()
}

dependencies {
    // ...
    compile 'foo.bar.baz:project:0.0.1-SNAPSHOT:osx-x86_64' 
}

and try to build, gradle says it can’t find the file:

$ ./gradlew clean build
> Task :compileJava FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':compileJava'.
> Could not resolve all files for configuration ':compileClasspath'.
   > Could not find foo.bar.baz:project:0.0.1-SNAPSHOT.
     Searched in the following locations:
       ...
       - file:/Users/erip/.m2/repository/foo/bar/baz/project/0.0.1-SNAPSHOT/project-0.0.1-SNAPSHOT.pom
     Required by:
         project :

It looks in an existing pom, but fails to resolve the jar, so why can't gradle find this dependency?

Answer 1

Resolving dependencies with classifiers is currently not supported by Gradle as of 6.8 as corroborated by this issue.

Answer 2

Re os-maven-plugin: The Java System Properties:

• os.name
• os.arch
• os.version

are available in POMs. Aren't these enough for your artifact classifiers?

Re your not found dependency: The Gradle dependencies doc mentions classifiers just in conjunction with JavaScript. The examples for dependencies there use just <groupId>:<artifactId>:<version>. (Where did you get the 3-colon syntax with the additional :<classifier>?) The POM Reference mentions classifiers/qualifiers as part of the version, so I'd try:

dependencies {
    // ...
    compile 'foo.bar.baz:project:0.0.1-SNAPSHOT-osx-x86_64' 
}