align behavior with semanticdb-scalac: last arg wins

[bjaglin]

Should fix #1110, as failure to look up the target root triggers the presentation compiler, with a version that might not match the bytecode injected (see #998).

The SemanticDBPlugin from sbt 1.3.x duplicates the targetroot option on Test (or any configuration that extends one where scalafix is enabled) via parent configuration delegation.: https://github.com/sbt/sbt/blob/a1b54d027a87654cbc782270872afc1b4c5a8852/main/src/main/scala/sbt/plugins/SemanticdbPlugin.scala#L42-L45.

In that case, semanticdb-scalac picks the last: https://github.com/scalameta/scalameta/blob/de206a796c7558f0ceb8bf3a557f3296f0ac34de/semanticdb/scalac/library/src/main/scala/scala/meta/internal/semanticdb/scalac/ConfigOps.scala#L105-L106, while scalafix was picking the first.

[daddykotex]

Thanks to you, I could include a work around in the meantime:

lazy val scalaFixTestWorkAround = Def.settings(
  scalacOptions in Test := {
    val initial = (scalacOptions in Test).value
    val semanticDbOptions = initial.filter(_.contains("-P:semanticdb:"))
    val semanticDbLess = initial.filterNot(_.contains("-P:semanticdb:"))
    semanticDbLess ++ semanticDbOptions.lastOption.toSeq
  }
)

Then use as .settings(scalaFixTestWorkAround) on the modules you need.

[bjaglin]

@daddykotex using the sbt 1.2.x way should also do the trick since the "problem" is in the sbt 1.3.x plugin:

 lazy val myproject = project.settings(
   scalaVersion := "2.12.11", // 2.11.12, or 2.13.2
+  addCompilerPlugin(scalafixSemanticdb), // enable SemanticDB
   scalacOptions ++= List(
+    "-Yrangepos",          // required by SemanticDB compiler plugin
+    "-Ywarn-unused-import" // required by `RemoveUnused` rule
   )
 )

https://scalacenter.github.io/scalafix/docs/users/installation.html#sbt

[olafurpg]

LGTM 👍 thank you!

I apologize the late response, if you're blocked by review in other PRs maybe @mlachkar can help?