Macro refactoring (#117) (#119)

* Add test code failing on compilation with Scala.JS (#117)

* Comment about #117

* Workaround for #116

* Sanity refactor (see #92)

* Update CI config

.travis.yml

@@ -1,6 +1,6 @@
 language: scala
 scala:
-- 2.12.2
+- 2.12.4
 - 2.11.11
 - 2.10.6
 jdk:

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

@@ -48,9 +48,11 @@ import scala.reflect.macros.blackbox
   @deprecated("Use implicitConfigReadsImpl or withOptionsReadsImpl", "2.6.6")
   protected def readsImpl[A: c.WeakTypeTag, O: c.WeakTypeTag]: c.Expr[Reads[A]] = macroImpl[A, Reads, Reads](
     implicitOptionsConfig, "read", "map", reads = true, writes = false)
+
   @deprecated("Use implicitConfigWritesImpl or withOptionsWritesImpl", "2.6.6")
   protected def writesImpl[A: c.WeakTypeTag, O: c.WeakTypeTag]: c.Expr[OWrites[A]] = macroImpl[A, OWrites, Writes](
     implicitOptionsConfig, "write", "contramap", reads = false, writes = true)
+
   @deprecated("Use implicitConfigFormatImpl or withOptionsFormatImpl", "2.6.6")
   protected def formatImpl[A: c.WeakTypeTag, O: c.WeakTypeTag]: c.Expr[OFormat[A]] = macroImpl[A, OFormat, Format](
     implicitOptionsConfig, "format", "inmap", reads = true, writes = true)
@@ -95,10 +97,7 @@ import scala.reflect.macros.blackbox
     val libs = q"_root_.play.api.libs"
     val json = q"$libs.json"
     val syntax = q"$libs.functional.syntax"
-    val utilPkg = q"$json.util"
     val JsPath = q"$json.JsPath"
-    val Reads = q"$json.Reads"
-    val Writes = q"$json.Writes"
     val unlift = q"$syntax.unlift"
     val atpe = atag.tpe.dealias
 
@@ -577,20 +576,26 @@ import scala.reflect.macros.blackbox
           cq"""x: $t => {
             val xjs = implicitly[Writes[$t]].writes(x)
             @inline def jso = xjs match {
-              case xo @ JsObject(_) => xo
-              case jsv => JsObject(Seq("_value" -> jsv))
+              case xo @ $json.JsObject(_) => xo
+              case jsv => $json.JsObject(Seq("_value" -> jsv))
             }
 
-            jso + ("_type" -> JsString(${typeNaming(t)}))
+            jso + ("_type" -> $json.JsString(${typeNaming(t)}))
           }"""
         })
 
         // Use shadowing to eliminate the generated term itself
         // from the implicit scope, due to the contravariant/implicit issue:
         // https://groups.google.com/forum/#!topic/scala-language/ZE83TvSWpT4
 
+        val shadowName = TermName(term.name.decodedName.toString.trim)
+        // DO NOT directly use `term.name` as for some reason,
+        // the TermName is provided within Scala.JS is appended with a final ' '
+
         q"""{ v: ${atpe} =>
-          val ${term.name.asInstanceOf[TermName]} = "eliminatedImplicit"
+          def ${shadowName}: $json.OWrites[${atpe}] =
+            sys.error("Invalid implicit resolution")
+
           $cases
         }"""
       }

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

@@ -49,7 +49,7 @@ class MacroSpec extends WordSpec with MustMatchers
     }
 
     "as Format for a simple generic case class" in {
-      val fmt = Json.format[Lorem[Double]]
+      val fmt: OFormat[Lorem[Double]] = Json.format
 
       fmt.reads(Json.obj("ipsum" -> 0.123D, "age" -> 1)).get mustEqual Lorem(
         0.123D, 1
@@ -104,8 +104,8 @@ class MacroSpec extends WordSpec with MustMatchers
       implicit val simpleReads = Reads[Simple] { js =>
         (js \ "bar").validate[String].map(Simple(_))
       }
-      implicit val optionalReads: Reads[Optional] = Json.reads[Optional]
-      implicit val familyReads: Reads[Family] = Json.reads[Family]
+      implicit val optionalReads: Reads[Optional] = Json.reads
+      implicit val familyReads: Reads[Family] = Json.reads
 
       val simple = Simple("foo")
       val optional = Optional(None)
@@ -150,7 +150,7 @@ class MacroSpec extends WordSpec with MustMatchers
     }
 
     "as Format for a generic case class" in {
-      val fmt = Json.format[Lorem[Float]]
+      val fmt: Format[Lorem[Float]] = Json.format
 
       fmt.writes(Lorem(2.34F, 2)) mustEqual Json.obj(
         "ipsum" -> 2.34F, "age" -> 2
@@ -192,7 +192,12 @@ class MacroSpec extends WordSpec with MustMatchers
       implicit val simpleWrites = Writes[Simple] { simple =>
         Json.obj("bar" -> simple.bar)
       }
-      implicit val optionalWrites: OWrites[Optional] = Json.writes[Optional]
+
+      implicit val optionalWrites = Json.writes[Optional]
+      // Following won't work due to inferrence issue (see #117)
+      // with inheritance/contravariance/implicit resolution
+      //val _: OWrites[Optional] = Json.writes
+
       implicit val familyWrites: OWrites[Family] = Json.writes[Family]
 
       val simple = Simple("foo")
@@ -529,6 +534,16 @@ class MacroSpec extends WordSpec with MustMatchers
 
   sealed trait EmptyFamily
 
+  object FamilyCodec {
+    implicit val simpleWrites = Json.writes[Simple]
+    implicit val optionalWrites = Json.writes[Optional]
+
+    implicit val familyWrites = Json.writes[Family] // Failing:
+    /* java.lang.IllegalArgumentException:
+     requirement failed: familyWrites  is not a valid identifier
+     */
+  }
+
   object Foo {
     import shapeless.tag.@@