Add prefix method to Route/Routes (#2547)

Add nest method to `Route`/`Routes`

zio-http/src/main/scala/zio/http/Route.scala

@@ -17,6 +17,8 @@ package zio.http
 
 import zio._
 
+import zio.http.codec.PathCodec
+
 /*
  * Represents a single route, which has either handled its errors by converting
  * them into responses, or which has polymorphic errors, which must later be
@@ -207,6 +209,16 @@ sealed trait Route[-Env, +Err] { self =>
    */
   def location: Trace
 
+  def nest(prefix: PathCodec[Unit])(implicit ev: Err <:< Response): Route[Env, Err] =
+    self match {
+      case Provided(route, env)                     => Provided(route.nest(prefix), env)
+      case Augmented(route, aspect)                 => Augmented(route.nest(prefix), aspect)
+      case Handled(routePattern, handler, location) => Handled(routePattern.nest(prefix), handler, location)
+
+      case Unhandled(rpm, handler, zippable, location) =>
+        Unhandled(rpm.prefix(prefix), handler, zippable, location)
+    }
+
   final def provideEnvironment(env: ZEnvironment[Env]): Route[Any, Err] =
     Route.Provided(self, env)
 
@@ -316,6 +328,16 @@ object Route                   {
       Route.route[A, Env1](self)(handler)
     }
 
+    def prefix(path: PathCodec[Unit]): Builder[Env, A] =
+      new Builder[Env, A] {
+        type PathInput = self.PathInput
+        type Context   = self.Context
+
+        def routePattern: RoutePattern[PathInput]         = self.routePattern.nest(path)
+        def aspect: HandlerAspect[Env, Context]           = self.aspect
+        def zippable: Zippable.Out[PathInput, Context, A] = self.zippable
+      }
+
     def provideEnvironment(env: ZEnvironment[Env]): Route.Builder[Any, A] = {
       implicit val z = zippable
 

zio-http/src/main/scala/zio/http/RoutePattern.scala

@@ -122,6 +122,9 @@ final case class RoutePattern[A](method: Method, pathCodec: PathCodec[A]) { self
    */
   def matches(method: Method, path: Path): Boolean = decode(method, path).isRight
 
+  def nest(prefix: PathCodec[Unit]): RoutePattern[A] =
+    copy(pathCodec = prefix ++ pathCodec)
+
   /**
    * Renders the route pattern as a string.
    */

zio-http/src/main/scala/zio/http/Routes.scala

@@ -17,6 +17,8 @@ package zio.http
 
 import zio._
 
+import zio.http.codec.PathCodec
+
 /**
  * Represents a collection of routes, each of which is defined by a pattern and
  * a handler. This data type can be thought of as modeling a routing table,
@@ -90,6 +92,9 @@ final class Routes[-Env, +Err] private (val routes: Chunk[zio.http.Route[Env, Er
   def handleErrorCauseZIO(f: Cause[Err] => ZIO[Any, Nothing, Response])(implicit trace: Trace): Routes[Env, Nothing] =
     new Routes(routes.map(_.handleErrorCauseZIO(f)))
 
+  def nest(prefix: PathCodec[Unit])(implicit trace: Trace, ev: Err <:< Response): Routes[Env, Err] =
+    new Routes(self.routes.map(_.nest(prefix)))
+
   /**
    * Handles all typed errors in the routes by converting them into responses,
    * taking into account the request that caused the error. This method can be

zio-http/src/main/scala/zio/http/codec/PathCodec.scala

@@ -21,7 +21,7 @@ import scala.language.implicitConversions
 
 import zio._
 
-import zio.http.Path
+import zio.http._
 
 /**
  * A codec for paths, which consists of segments, where each segment may be a
@@ -48,6 +48,11 @@ sealed trait PathCodec[A] { self =>
   final def /[B](that: PathCodec[B])(implicit combiner: Combiner[A, B]): PathCodec[combiner.Out] =
     self ++ that
 
+  final def /[Env](routes: Routes[Env, Response])(implicit
+    ev: PathCodec[A] <:< PathCodec[Unit],
+  ): Routes[Env, Response] =
+    routes.nest(ev(self))
+
   final def asType[B](implicit ev: A =:= B): PathCodec[B] = self.asInstanceOf[PathCodec[B]]
 
   /**

zio-http/src/test/scala/zio/http/RouteSpec.scala

@@ -23,6 +23,16 @@ object RouteSpec extends ZIOHttpSpec {
   def extractStatus(response: Response): Status = response.status
 
   def spec = suite("RouteSpec")(
+    suite("Route#prefix")(
+      test("prefix should add a prefix to the route") {
+        val route =
+          Method.GET / "foo" -> handler(Response.ok)
+
+        val prefixed = route.nest("bar")
+
+        assertTrue(prefixed.isDefinedAt(Request.get(url"/bar/foo")))
+      },
+    ),
     suite("Route#sandbox")(
       test("infallible route does not change under sandbox") {
         val route =