Enable customization of Commands.Command shrinking

project/MimaSettings.scala

@@ -16,6 +16,9 @@ object MimaSettings {
   )
 
   private def newMethods = Seq(
+    "org.scalacheck.commands.Commands.shrinkCommand",
+    "org.scalacheck.commands.Commands.shrinkSequentialCommands",
+    "org.scalacheck.commands.Commands.shrinkParallelCommands",
   )
 
   private def removedPrivateMethods = Seq(

src/main/scala/org/scalacheck/commands/Commands.scala

@@ -262,6 +262,24 @@ trait Commands {
     * [[State]].  By default no shrinking is done for [[State]]. */
   def shrinkState: Shrink[State] = implicitly
 
+  /** Override this to provide a custom Shrinker for your internal
+    * [[Command]].  By default no shrinking is done for [[Command]]. */
+  def shrinkCommand: Shrink[Command] = implicitly
+
+  /** Override this to provide a custom Shrinker of sequential [[Command]]s.
+    * By default, the implicit List shrinker is used with [[shrinkCommand]]. */
+  def shrinkSequentialCommands: Shrink[List[Command]] = {
+    implicit val commandShrinker = shrinkCommand
+    implicitly
+  }
+
+  /** Override this to provide a custom Shrinker of parallel [[Command]]s.
+    * By default, the implict List shrinker is used with [[shrinkCommand]]. */
+  def shrinkParallelCommands: Shrink[List[List[Command]]] = {
+    implicit val commandShrinker = shrinkCommand
+    implicitly
+  }
+
   // Private methods //
   private type Commands = List[Command]
 
@@ -270,9 +288,12 @@ trait Commands {
   )
 
   private implicit val shrinkActions: Shrink[Actions] = Shrink[Actions] { as =>
+    val shrinkSeq = shrinkSequentialCommands
+    val shrinkPar = shrinkParallelCommands
+
     val shrinkedCmds: Stream[Actions] =
-      Shrink.shrink(as.seqCmds).map(cs => as.copy(seqCmds = cs)) append
-      Shrink.shrink(as.parCmds).map(cs => as.copy(parCmds = cs))
+      shrinkSeq.shrink(as.seqCmds).map(cs => as.copy(seqCmds = cs)) append
+      shrinkPar.shrink(as.parCmds).map(cs => as.copy(parCmds = cs))
 
     Shrink.shrinkWithOrig[State](as.s)(shrinkState) flatMap { state =>
       shrinkedCmds.map(_.copy(s = state))