Add exists & contains methods for JsResult (#178)

build.sbt

@@ -142,6 +142,8 @@ lazy val `play-json` = crossProject(JVMPlatform, JSPlatform).crossType(CrossType
       ProblemFilters.exclude[ReversedMissingMethodProblem]("play.api.libs.json.JsResult.recoverWith"),
       ProblemFilters.exclude[ReversedMissingMethodProblem]("play.api.libs.json.Writes.contramap"),
       ProblemFilters.exclude[ReversedMissingMethodProblem]("play.api.libs.json.OWrites.contramap"),
+      ProblemFilters.exclude[ReversedMissingMethodProblem]("play.api.libs.json.JsResult.contains"),
+      ProblemFilters.exclude[ReversedMissingMethodProblem]("play.api.libs.json.JsResult.exists"),
 
       // Scala 2.13.0-M4
       ProblemFilters.exclude[IncompatibleMethTypeProblem]("play.api.libs.json.LowPriorityDefaultReads.traversableReads"),

play-json/shared/src/main/scala/play/api/libs/json/JsResult.scala

@@ -21,6 +21,10 @@ case class JsSuccess[T](value: T, path: JsPath = JsPath()) extends JsResult[T] {
 
   def foreach(f: T => Unit): Unit = f(value)
 
+  def contains[AA >: T](elem: AA): Boolean = elem == value
+
+  def exists(p: T => Boolean): Boolean = p(value)
+
   def repath(path: JsPath): JsResult[T] = JsSuccess(value, path ++ this.path)
 
   def getOrElse[U >: T](t: => U): U = value
@@ -63,6 +67,10 @@ case class JsError(errors: collection.Seq[(JsPath, collection.Seq[JsonValidation
 
   def foreach(f: Nothing => Unit): Unit = ()
 
+  def contains[AA >: Nothing](elem: AA): Boolean = false
+
+  def exists(p: Nothing => Boolean): Boolean = false
+
   def repath(path: JsPath): JsResult[Nothing] =
     JsError(errors.map { case (p, s) => path ++ p -> s })
 
@@ -207,6 +215,12 @@ sealed trait JsResult[+A] { self =>
     def withFilter(q: A => Boolean) = new WithFilter(a => p(a) && q(a))
   }
 
+  /** If this result is successful than checks for presence for '''elem''', otherwise return '''false''' */
+  def contains[AA >: A](elem: AA): Boolean
+
+  /** If this result is successful than check value with predicate '''p''', otherwise return '''false''' */
+  def exists(p: A => Boolean): Boolean
+
   /** Updates the JSON path */
   def repath(path: JsPath): JsResult[A]
 

play-json/shared/src/test/scala/play/api/libs/json/JsResultSpec.scala

@@ -48,4 +48,33 @@ class JsResultSpec extends WordSpec with MustMatchers {
       JsError("err").recoverWith { _ => succ } mustEqual succ
     }
   }
+
+  "JsResult" should {
+
+    "return true for JsSuccess(x)#contains(x)" in {
+      assert(JsSuccess(1).contains(1))
+    }
+
+    "return false for JsSuccess(x)#contains(y)" in {
+      assert(!JsSuccess(1).contains(2))
+    }
+
+    "return false for JsError(_)#contains(_)" in {
+      assert(!JsError().contains(1))
+    }
+
+    "return true for JsSuccess(x)#exists(p) if p(x) == true" in {
+      assert(JsSuccess(1).exists(_ == 1))
+    }
+
+    "return false for JsSuccess(x)#exists(p) if p(x) == false" in {
+      assert(!JsSuccess(1).exists(_ == 2))
+    }
+
+    "return false for JsError(_).exists(_)" in {
+      assert(!JsError().exists(_ == 1))
+    }
+
+  }
+
 }