Merge pull request #876 from cchantep/feature/jsobj_builder

Add Json.newBuilder utility

docs/manual/working/scalaGuide/main/json/ScalaJson.md

@@ -73,6 +73,10 @@ Represents a path into a `JsValue` structure, analogous to XPath for XML. This i
 
 @[convert-from-factory](code/ScalaJsonSpec.scala)
 
+You also can use `Json.newBuilder` to create `JsObject`:
+
+@[object-builder](code/ScalaJsonSpec.scala)
+
 ### Using Writes converters
 
 Scala to `JsValue` conversion is performed by the utility method `Json.toJson[T](T)(implicit writes: Writes[T])`. This functionality depends on a converter of type [`Writes[T]`](api/scala/play/api/libs/json/Writes.html) which can convert a `T` to a `JsValue`.

docs/manual/working/scalaGuide/main/json/code-2/Scala2JsonAutomatedSpec.scala

@@ -4,7 +4,6 @@
 
 package scalaguide.json
 
-import play.api.libs.json.Json
 import org.specs2.mutable.Specification
 
 //#valueClass

docs/manual/working/scalaGuide/main/json/code/ScalaJsonSpec.scala

@@ -45,8 +45,9 @@ class ScalaJsonSpec extends Specification {
     "parse json" in {
       import play.api.libs.json._
       val json = sampleJson
-      (json \ "name").get.must_==(JsString("Watership Down"))
-      (json \ "location" \ "lat").get.must_==(JsNumber(51.235685))
+
+      (json \ "name").toOption mustEqual Some(JsString("Watership Down"))
+      (json \ "location" \ "lat").toOption mustEqual Some(JsNumber(51.235685))
     }
 
     "allow constructing json using case classes" in {
@@ -78,17 +79,15 @@ class ScalaJsonSpec extends Specification {
         )
       )
       //#convert-from-classes
-      (json \ "name").get.must_==(JsString("Watership Down"))
+
+      (json \ "name").toOption mustEqual Some(JsString("Watership Down"))
     }
 
     "allow constructing json using factory methods" in {
       //#convert-from-factory
-      import play.api.libs.json.JsNull
-      import play.api.libs.json.Json
-      import play.api.libs.json.JsString
-      import play.api.libs.json.JsValue
+      import play.api.libs.json.{JsNull,Json,JsString,JsObject}
 
-      val json: JsValue = Json.obj(
+      val json: JsObject = Json.obj(
         "name"     -> "Watership Down",
         "location" -> Json.obj("lat" -> 51.235685, "long" -> -1.309197),
         "residents" -> Json.arr(
@@ -105,7 +104,44 @@ class ScalaJsonSpec extends Specification {
         )
       )
       //#convert-from-factory
-      (json \ "name").get.must_==(JsString("Watership Down"))
+
+      (json \ "name").toOption mustEqual Some(JsString("Watership Down"))
+    }
+
+    "allow constructing json using builder" in {
+      //#object-builder
+      import play.api.libs.json.{ JsNull, Json, JsString, JsObject }
+
+      def asJson(active: Boolean): JsObject = {
+        val builder = Json.newBuilder
+
+        builder ++= Seq(
+          "name" -> "Watership Down",
+          "location" -> Json.obj(
+            "lat" -> 51.235685D, "long" -> -1.309197D))
+
+        if (active) {
+          builder += "active" -> true
+        }
+
+        builder += "residents" -> Seq(
+          Json.obj(
+            "name" -> "Fiver",
+            "age"  -> 4,
+            "role" -> JsNull
+          ),
+          Json.obj(
+            "name" -> "Bigwig",
+            "age"  -> 6,
+            "role" -> "Owsla"
+          ))
+
+        builder.result()
+      }
+      //#object-builder
+
+      (asJson(true) \ "name").
+        toOption mustEqual Some(JsString("Watership Down"))
     }
 
     "allow converting simple types" in {
@@ -171,7 +207,7 @@ class ScalaJsonSpec extends Specification {
       val json = Json.toJson(place)
       //#convert-from-model
 
-      (json \ "name").get === JsString("Watership Down")
+      (json \ "name").toOption === Some(JsString("Watership Down"))
     }
 
     "allow converting models preferred" in {
@@ -211,27 +247,28 @@ class ScalaJsonSpec extends Specification {
       val json = Json.toJson(place)
       //#convert-from-model
 
-      (json \ "name").get === JsString("Watership Down")
+      (json \ "name").toOption === Some(JsString("Watership Down"))
     }
 
     "allow traversing JsValue tree" in {
       import play.api.libs.json._
       val json = sampleJson
 
       //#traverse-simple-path
-      val lat = (json \ "location" \ "lat").get
-      // returns JsNumber(51.235685)
-      val bigwig = (json \ "residents" \ 1).get
-      // returns {"name":"Bigwig","age":6,"role":"Owsla"}
+      val lat = (json \ "location" \ "lat").toOption
+      // returns some JsNumber(51.235685)
+      val bigwig = (json \ "residents" \ 1).toOption
+      // returns some {"name":"Bigwig","age":6,"role":"Owsla"}
 
       //#traverse-simple-path
 
       val expected = Json.parse(
         """{"name":"Bigwig","age":6,"role":"Owsla"}"""
       )
-      bigwig.mustEqual(expected)
 
-      lat === JsNumber(51.235685)
+      bigwig mustEqual Some(expected)
+
+      lat === Some(JsNumber(51.235685))
 
       //#traverse-recursive-path
       val names = json \\ "name"
@@ -282,7 +319,8 @@ class ScalaJsonSpec extends Specification {
         case _: NoSuchElementException =>
       }
 
-      (bigwig \ "name").get === JsString("Bigwig")
+      bigwig.flatMap(
+        obj => (obj \ "name").toOption) === Some(JsString("Bigwig"))
     }
 
     "allow converting JsValue to String" in {

play-json/shared/src/main/scala-2.13+/play/api/libs/json/JsObjectBuilder.scala

@@ -0,0 +1,38 @@
+/*
+ * Copyright (C) from 2022 The Play Framework Contributors <https://github.com/playframework>, 2011-2021 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package play.api.libs.json
+
+import scala.collection.mutable.{ Builder => MBuilder }
+
+private[json] final class JsObjectBuilder extends MBuilder[(String, Json.JsValueWrapper), JsObject] {
+
+  private val fs = Map.newBuilder[String, JsValue]
+
+  def addOne(elem: (String, Json.JsValueWrapper)): this.type = {
+    val (name, wrapped) = elem
+
+    fs += (name -> Json.unwrap(wrapped))
+
+    this
+  }
+
+  override def addAll(xs: IterableOnce[(String, Json.JsValueWrapper)]): this.type = {
+    xs.iterator.foreach(addOne)
+
+    this
+  }
+
+  override def knownSize: Int = fs.knownSize
+
+  override def sizeHint(size: Int): Unit = {
+    fs.sizeHint(size)
+  }
+
+  def clear(): Unit = {
+    fs.clear()
+  }
+
+  def result(): JsObject = JsObject(fs.result())
+}

play-json/shared/src/main/scala-2.13-/play/api/libs/json/JsObjectBuilder.scala

@@ -0,0 +1,34 @@
+/*
+ * Copyright (C) from 2022 The Play Framework Contributors <https://github.com/playframework>, 2011-2021 Lightbend Inc. <https://www.lightbend.com>
+ */
+
+package play.api.libs.json
+
+import scala.collection.mutable.{ Builder => MBuilder }
+
+private[json] final class JsObjectBuilder extends MBuilder[(String, Json.JsValueWrapper), JsObject] {
+
+  private val fs = Map.newBuilder[String, JsValue]
+
+  def +=(elem: (String, Json.JsValueWrapper)): this.type = {
+    val (name, wrapped) = elem
+
+    fs += (name -> Json.unwrap(wrapped))
+
+    this
+  }
+
+  override def ++=(xs: TraversableOnce[(String, Json.JsValueWrapper)]): this.type = {
+    xs.foreach(`+=`)
+
+    this
+  }
+
+  def knownSize: Int = fs.result().size
+
+  def clear(): Unit = {
+    fs.clear()
+  }
+
+  def result(): JsObject = JsObject(fs.result())
+}

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

@@ -4,6 +4,8 @@
 
 package play.api.libs.json
 
+import scala.collection.mutable.{ Builder => MBuilder }
+
 import java.io.InputStream
 
 /**
@@ -226,12 +228,52 @@ object Json extends JsonFacade with JsMacros with JsValueMacros {
   implicit def toJsFieldJsValueWrapper[T](field: T)(implicit w: Writes[T]): JsValueWrapper =
     JsValueWrapperImpl(w.writes(field))
 
-  def obj(fields: (String, JsValueWrapper)*): JsObject = JsObject(fields.map(f => (f._1, unwrap(f._2))))
+  def obj(fields: (String, JsValueWrapper)*): JsObject = JsObject(fields.map { case (name, wrapped) =>
+    name -> unwrap(wrapped)
+  })
+
+  /**
+   * Returns a JSON object builder.
+   *
+   * {{{
+   *   import play.api.libs.json.{ Json, JsObject }
+   *
+   *   // Create a new builder
+   *   val builder: JsObjectBuilder = JsObject.newBuilder
+   *
+   *   // Add key-value pairs to the builder
+   *   builder += ("name" -> "John Doe")
+   *   builder += ("age" -> 25)
+   *
+   *   // Clear the builder
+   *   builder.clear()
+   *
+   *   // Add more key-value pairs
+   *   builder += ("email" -> "john.doe@example.com")
+   *   builder += ("address" -> "123 Street")
+   *
+   *   // Build the final JsObject
+   *   val result: JsObject = builder.result()
+   *
+   *   // Print the resulting JsObject
+   *   println(result)
+   * }}}
+   *
+   * This will output:
+   * {{{
+   *   {"email":"john.doe@example.com","address":"123 Street"}
+   * }}}
+   */
+  def newBuilder: MBuilder[(String, Json.JsValueWrapper), JsObject] =
+    new JsObjectBuilder()
 
   def arr(items: JsValueWrapper*): JsArray = JsArray(items.iterator.map(unwrap).toArray[JsValue])
 
-  // Passed nulls will typecheck without needing the implicit conversion, so they need to checked at runtime
-  private def unwrap(wrapper: JsValueWrapper) = wrapper match {
+  /*
+   * Passed nulls will typecheck without needing the implicit conversion,
+   * so they need to checked at runtime.
+   */
+  private[json] def unwrap(wrapper: JsValueWrapper) = wrapper match {
     case null                      => JsNull
     case JsValueWrapperImpl(value) => value
   }

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

@@ -135,6 +135,22 @@ class JsonSharedSpec extends AnyWordSpec with Matchers with org.scalatestplus.sc
       "js.toJsObject(peach)(writes)".mustNot(typeCheck)
     }
 
+    "create object using builder" in {
+      val builder = Json.newBuilder
+
+      builder += ("name" -> "John Doe")
+      builder += ("age"  -> 25)
+
+      val result: JsObject = builder.result()
+
+      result.mustEqual(
+        Json.obj(
+          "name" -> "John Doe",
+          "age"  -> 25
+        )
+      )
+    }
+
     "convert to a byte array containing the UTF-8 representation" in json { js =>
       val json = js.parse("""
                             |{