Fix #72.

This allows users to add custom rewrites to the compiler classpath and
classload them by fully qualified name.

core/src/main/scala/scalafix/config/ScalafixMetaconfigReaders.scala

@@ -9,6 +9,7 @@ import scala.util.matching.Regex
 import scalafix.Failure.UnknownRewrite
 import scalafix.rewrite.ScalafixRewrite
 import scalafix.rewrite.ScalafixRewrites
+import scalafix.util.ClassloadObject
 import scalafix.util.TreePatch._
 
 import metaconfig.Reader
@@ -26,7 +27,13 @@ trait ScalafixMetaconfigReaders {
  }
 
  implicit lazy val rewriteReader: Reader[ScalafixRewrite] =
- ReaderUtil.fromMap(ScalafixRewrites.name2rewrite)
+ Reader.instance[ScalafixRewrite] {
+ case fqn: String if fqn.startsWith("_root_.") =>
+ val suffix = if (fqn.endsWith("$")) "" else "$"
+ ClassloadObject[ScalafixRewrite](fqn.stripPrefix("_root_.") + suffix)
+ case els =>
+ ReaderUtil.fromMap(ScalafixRewrites.name2rewrite).read(els)
+ }
 
  implicit val RegexReader: Reader[Regex] = Reader.instance[Regex] {
  case str: String => Right(FilterMatcher.mkRegexp(List(str)))

core/src/main/scala/scalafix/util/ClassloadObject.scala

@@ -0,0 +1,48 @@
+package scalafix.util
+
+import scala.collection.immutable.Seq
+import scala.reflect.ClassTag
+import scala.util.Failure
+import scala.util.Success
+import scala.util.Try
+
+import java.lang.reflect.InvocationTargetException
+
+// Helper to classload object or no argument class.
+class ClassloadObject[T](classLoader: ClassLoader)(implicit ev: ClassTag[T]) {
+ private val t = ev.runtimeClass
+
+ private def getClassFor(fqcn: String): Try[Class[_ <: T]] =
+ Try[Class[_ <: T]]({
+ val c =
+ Class.forName(fqcn, false, classLoader).asInstanceOf[Class[_ <: T]]
+ if (t.isAssignableFrom(c)) c
+ else throw new ClassCastException(s"$t is not assignable from $c")
+ })
+
+ private def createInstanceFor(clazz: Class[_]): Try[T] =
+ Try {
+ val constructor = clazz.getDeclaredConstructor()
+ constructor.setAccessible(true)
+ val obj = constructor.newInstance()
+ if (t.isInstance(obj)) obj.asInstanceOf[T]
+ else
+ throw new ClassCastException(
+ s"${clazz.getName} is not a subtype of $t")
+ } recover {
+ case i: InvocationTargetException if i.getTargetException ne null ⇒
+ throw i.getTargetException
+ }
+
+ def createInstanceFor(fqcn: String): Try[T] =
+ getClassFor(fqcn).flatMap(c => createInstanceFor(c))
+}
+
+object ClassloadObject {
+ def apply[T: ClassTag](fqn: String): Either[Throwable, T] =
+ new ClassloadObject(this.getClass.getClassLoader)
+ .createInstanceFor(fqn) match {
+ case Success(e) => Right(e)
+ case Failure(e) => Left(e)
+ }
+}

scalafix-nsc/src/test/resources/checkSyntax/FqnRewrite.source

@@ -0,0 +1,9 @@
+rewrites = [
+ _root_.scalafix.test.FqnRewrite
+]
+<<< NOWRAP add import
+import scala._
+object FqnMe
+>>>
+import scala.meta._
+object FqnMe

scalafix-nsc/src/test/scala/scalafix/test/FqnRewrite.scala

@@ -0,0 +1,13 @@
+package scalafix.test
+
+import scala.meta._
+import scala.collection.immutable.Seq
+import scalafix.rewrite.Rewrite
+import scalafix.rewrite.RewriteCtx
+import scalafix.util.Patch
+import scalafix.util.TreePatch.AddGlobalImport
+
+case object FqnRewrite extends Rewrite[Any] {
+ override def rewrite[B <: Any](ctx: RewriteCtx[B]): Seq[Patch] =
+ Seq(AddGlobalImport(importer"scala.meta._"))
+}