Add forall method to JsResult with Option#forall semantics (#184)

build.sbt

@@ -144,6 +144,7 @@ lazy val `play-json` = crossProject(JVMPlatform, JSPlatform).crossType(CrossType
       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"),
+      ProblemFilters.exclude[ReversedMissingMethodProblem]("play.api.libs.json.JsResult.forall"),
 
       // 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

@@ -25,6 +25,8 @@ case class JsSuccess[T](value: T, path: JsPath = JsPath()) extends JsResult[T] {
 
   def exists(p: T => Boolean): Boolean = p(value)
 
+  def forall(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
@@ -71,6 +73,8 @@ case class JsError(errors: collection.Seq[(JsPath, collection.Seq[JsonValidation
 
   def exists(p: Nothing => Boolean): Boolean = false
 
+  def forall(p: Nothing => Boolean): Boolean = true
+
   def repath(path: JsPath): JsResult[Nothing] =
     JsError(errors.map { case (p, s) => path ++ p -> s })
 
@@ -221,6 +225,12 @@ sealed trait JsResult[+A] { self =>
   /** If this result is successful than check value with predicate '''p''', otherwise return '''false''' */
   def exists(p: A => Boolean): Boolean
 
+  /**
+   * If this result is successful than check value with predicate '''p''', otherwise return '''true'''.
+   * Follows [[scala.collection.Traversable.forall]] semantics
+   */
+  def forall(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

@@ -77,4 +77,24 @@ class JsResultSpec extends WordSpec with MustMatchers {
 
   }
 
+  "JsSuccess#forall" should {
+
+    "return true for JsSuccess(x * 2).forall(_ % 2 == 0)" in {
+      assert(JsSuccess(2).forall(_ % 2 == 0))
+    }
+
+    "return false for JsSuccess(x, {x < 0}).forall(_ >)" in {
+      assert(!JsSuccess(-1).forall(_ > 0))
+    }
+
+  }
+
+  "JsError#forall" should {
+
+    "return true" in {
+      assert(JsError("").forall(_ => false))
+    }
+
+  }
+
 }