Make the current artifact configurable and default to use the jar (#…

…143)

* Make the current artifact configurable.

This enhances the flexibility of the plugin.

* Change the default for `mimaCurrentArtifact` to `jar`

This is to also take all potential post processing (filtering, shading, OSGi bundling) into account.
This is IMHO a better default than `compile().classes`, but if someone needs the old behavior, it's now configurable.

* doc

* ScalaDoc

* scalafmt

README.md

@@ -104,6 +104,18 @@ def mimaPreviousArtifacts = Agg(
 )
 ```
 
+### mimaCurrentArtifact
+
+The `PathRef` to the actual artifact that is being checked for binary compatibility. Defaults to use the result of the `jar` target.
+
+_Up until version `0.0.24`, this was implemented as `compile().classes`, for compatibility to the sbt plugin._
+
+```scala
+def mimaCurrentArtifact = T {
+  compile().classes
+}
+```
+
 ### mimaBackwardIssueFilters
 
 Filters to apply to binary issues found grouped by version of a module

mill-mima/src/com/github/lolgab/mill/mima/MimaBase.scala

@@ -105,6 +105,14 @@ private[mima] trait MimaBase
     MimaWorkerExternalModule.mimaWorker().impl(cp)
   }
 
+  /** The `PathRef` to the actual artifact that is being checked for binary
+    * compatibility. Defaults to use the result of the [[jar]] target.
+    *
+    * Up until version mill-mima `0.0.24`, this was implemented as
+    * [[compile]]`().classes`, for compatibility to the sbt plugin.
+    */
+  def mimaCurrentArtifact: T[PathRef] = T { jar() }
+
   def mimaReportBinaryIssues(): Command[Unit] = T.command {
     def prettyDep(dep: Dep): String = {
       s"${dep.dep.module.orgName}:${dep.dep.version}"
@@ -116,7 +124,7 @@ private[mima] trait MimaBase
       log.outputStream.println(_)
     val runClasspathIO =
       runClasspath().view.map(_.path).filter(os.exists).map(_.toIO).toArray
-    val current = compile().classes.path.pipe {
+    val current = mimaCurrentArtifact().path.pipe {
       case p if os.exists(p) => p
       case _                 => (T.dest / "emptyClasses").tap(os.makeDir)
     }.toIO