[MASSEMBLY-993] Configuration option to specify artifact classifier.

**[Garret Wilson](https://issues.apache.org/jira/secure/ViewProfile.jspa?name=garretwilson)** opened **[MASSEMBLY-993](https://issues.apache.org/jira/browse/MASSEMBLY-993?redirect=false)** and commented

Please add a `classifier` option to the Maven Assembly Plugin, similar to the [Spring Boot Maven Plugin option of the same name](https://docs.spring.io/spring-boot/docs/current/maven-plugin/reference/htmlsingle/#goals-repackage-parameters-details-classifier), to allow a POM to explicitly indicate what classifier to append to the end of the artifact.

Generated Maven artifacts have an option of a "classifier" such as `javadoc` or `sources`. This is placed on the end of a artifact base filename, such as `foo-1.2.3-javadoc.jar` or `foo-1.2.3-sources`. See the description of classifiers in the [Maven POM Reference](https://maven.apache.org/pom.html) for more details.

The Spring Boot Maven Plugin has a simple [configuration to set the classifier](https://docs.spring.io/spring-boot/docs/current/maven-plugin/reference/htmlsingle/#goals-repackage-parameters-details-classifier). Thus if I specify `bar` as my classifier, then Spring Boot Maven Plugin generates `foo-1.2.3-bar.jar`.

The Maven Assembly Plugin's only equivalent facility is indirect and arguably semantically incorrect. Instead of specifying a "classifier", the Assembly Plugin has a Boolean option to [append the assembly ID](https://maven.apache.org/plugins/maven-assembly-plugin/single-mojo.html#appendAssemblyId). The name of this option is a little unclear; what it's really saying is "use the assembly ID as the artifact classifier". Using the assembly ID as the classifier is not a bad default, but the problem is not allowing an option for an alternate classifier.

The drawback here is that the consumer of a public, published assembly descriptor _has no control over what the ID is defined within the descriptor_. There needs to be a way to specify the generated artifact classifier _at the point of plugin definition_, independent of what is defined in the descriptor. (Of course, if MASSEMBLY-992 were implemented, this would provide one workaround, although not solve the problem of consuming published artifact descriptors.)

As an example see https://github.com/symphoniacloud/lambda-packaging/issues/1 . Symphonia publishes a Maven Assembly Plugin descriptor, but the ID it uses (for reasons I outline in that ticket) is less than ideal. If the Assembly Plugin simply were to allow a `classifier` option like Spring Boot Maven Plugin does, the POM could simply choose whatever it wants, independent of the ID in the assembly descriptor.

---
No further details from [MASSEMBLY-993](https://issues.apache.org/jira/browse/MASSEMBLY-993?redirect=false)

Start with the Maven Assembly Plugin configuration for appendAssemblyId and the artifact naming behavior it controls. Trace how the assembly descriptor ID becomes the classifier, then determine where a plugin-level classifier option belongs. Done means a POM can choose a classifier independently of the descriptor ID while existing appendAssemblyId behavior remains supported.

Written by the indexing model from the issue text.