#19301 Support packaging JVM artifacts for first party sources. Issue created by alonsodomin Is your feature request related to a problem? Please describe. Support additional targets like `jvm_jar`/`scala_jar` with the purpose of packaging compiled JVM sources into JAR artifacts that can be published into a Maven 2 compatible repository. Building JARs and publishing them is bread and butter in the JVM world and can be helpful in many scenarios but most beneficial in the following two: • Library authors, specially multi-module frameworks, that want to have a single repo for all their sources (for consistency purposes) but want to offer a mix and match selection of features to their users. • An organization wants to move from a repo-per-project structure to a monorepo but wants do to do that gradually so they can move repos one at a time. Without this feature they only have an all or nothing approach. Describe the solution you'd like The bare minimum would be being able to declare JAR artifact targets like in the following scenario:

jvm_artifact(name="thrid_party_1", group=..., artifact=...) # simplified for sake of brevity
jvm_artifact(name="third_party_2")

java_sources(name="core_src", dependencies=[":third_party_1"])
java_sources(name="extra_src", dependencies=[":core_src", ":third_party_2"])

jvm_jar(name="core_jar", group="<http://my.org|my.org>", arfifact="core", version="1.0", dependencies=[":core_src"])
jvm_jar(name="extra_jar", group="<http://my.org|my.org>", arfifact="core", version="1.0", dependencies=[":core_jar", ":extra_src"])

With the previous, when running

pants package ::

, Pants would build two JAR artifacts, the ones for targets

core_jar

and

extra_jar

with only the minimal compiled sources according to the dependency graph that still produce a valid class path. So, since

core_jar

depends on

core_src

, it will contain only the class files for the

core_src

target AND NOT the class files for the third party dependency. In the case of

extra_jar

a similar thing happens but also the class files for

core_src

WILL NOT be part of the final JAR as they are already satisfied by the dependency on

core_jar

. The built JARs should be publishable into a Maven 2 compatible repository. This could be achieved by leveraging Apache Ivy which would also give the possibility to publish to non-Maven repos. The choice of underlying mechanism is left open though but it's considered to be crucial for this feature as there is little value on creating JAR files that are not shared with others. Important to note is that to achieve the Maven 2 compatibility, Pants will need to generate a POM file and package it inside the JAR. Additionally, the

jvm_jar

target should support being runnable (having a

main

field). A

scala_jar

target type should also be supported at some point since, similar to the

scala_artifact

target, Scala JAR names need to be decorated with the Scala version. While this can be done using the simpler

jvm_jar

target and resolves, a

scala_jar

specific target simplifies it a lot. Describe alternatives you've considered There isn't much alternative right now, organisations that want to publish JARs need to rely on secondary tools to perform that specific task or just stick with their original built tool of choice (i.e. Maven, Gradle, SBT, ...). For those that really want to transition to Pants, the path of less resistance is to use

deploy_jar

to build massive JARs and then use Apache Ant to unpack them and build smaller JARs based on folder structure. Additional context Authenticating with password-protected Maven 2 repositories at the time of publishing the JARs is out of scope at this point. pantsbuild/pants