Render typeclass; 9.5.8

build.sbt

@@ -1,7 +1,7 @@
 lazy val scalalib = Project("scalalib", file("."))
 organization                           := "com.github.ornicar"
 name                                   := "scalalib"
-version                                := "9.5.7"
+version                                := "9.5.8"
 scalaVersion                           := "3.3.3"
 licenses += "MIT"                      -> url("https://opensource.org/licenses/MIT")
 libraryDependencies += "org.typelevel" %% "cats-core"      % "2.10.0"

src/main/scala/Render.scala

@@ -0,0 +1,18 @@
+package ornicar.scalalib
+
+/* Like cats.Show,
+ * except it's actually fine to render it to an end-user.
+ * cats.Show has a default instance for Option[A] that renders
+ * as `None` or `Some(value)`, which is not very user-friendly.
+ */
+@FunctionalInterface
+trait Render[A]:
+  def apply(a: A): String
+  extension (a: A) def render: String = apply(a)
+
+object Render:
+  def apply[A](f: A => String): Render[A] = f(_)
+
+  /* If we have Render, we have Show;
+   * but not the other way around. */
+  given [A](using Render[A]): cats.Show[A] = cats.Show.show(_.render)

src/main/scala/newtypes.scala

@@ -44,7 +44,8 @@ object newtypes:
     extension (a: Newtype) inline def apply: Impl = a
 
   trait OpaqueString[A](using A =:= String) extends TotalWrapper[A, String]:
-    given Show[A] = Show.show(_.value)
+    given Show[A]   = _.value
+    given Render[A] = _.value
 
   trait OpaqueInt[A](using A =:= Int) extends TotalWrapper[A, Int]:
     extension (inline a: A)