From 3bc1436155cd6d5c046002c12ab1a65ee4fe1e71 Mon Sep 17 00:00:00 2001
From: Filippo De Luca <me@filippodeluca.com>
Date: Tue, 16 May 2023 18:23:23 +0200
Subject: [PATCH] Allow overriding builtin scalars

Ref: #1000
---
 .../schema/AstSchemaMaterializer.scala        | 24 +++++++---
 .../sangria/schema/CustomScalarSpec.scala     | 45 +++++++++++++++++++
 2 files changed, 62 insertions(+), 7 deletions(-)

diff --git a/modules/core/src/main/scala/sangria/schema/AstSchemaMaterializer.scala b/modules/core/src/main/scala/sangria/schema/AstSchemaMaterializer.scala
index 7c77c70a..45db33aa 100644
--- a/modules/core/src/main/scala/sangria/schema/AstSchemaMaterializer.scala
+++ b/modules/core/src/main/scala/sangria/schema/AstSchemaMaterializer.scala
@@ -576,10 +576,10 @@ class AstSchemaMaterializer[Ctx] private (
   def getNamedType(
       origin: MatOrigin,
       typeName: String,
-      location: Option[AstLocation]): Type with Named =
-    typeDefCache.getOrElseUpdate(
-      origin -> typeName,
-      Schema.getBuiltInType(typeName).getOrElse {
+      location: Option[AstLocation]): Type with Named = {
+
+    def update = {
+      val builtType = {
         val existing = existingDefsMat.get(typeName).toVector
         val sdl = typeDefsMat.filter(_.name == typeName)
         val additional = builder.additionalTypes.filter(_.name == typeName).toVector
@@ -606,11 +606,21 @@ class AstSchemaMaterializer[Ctx] private (
             getNamedType(origin, allCandidates.head)
           } else None
 
-        builtType.getOrElse(
-          throw MaterializedSchemaValidationError(Vector(
-            UnknownTypeViolation(typeName, Seq.empty, document.sourceMapper, location.toList))))
+        builtType
       }
+
+      builtType
+        .orElse(Schema.getBuiltInType(typeName))
+        .getOrElse(throw MaterializedSchemaValidationError(Vector(
+          UnknownTypeViolation(typeName, Seq.empty, document.sourceMapper, location.toList))))
+
+    }
+
+    typeDefCache.getOrElseUpdate(
+      origin -> typeName,
+      update
     )
+  }
 
   def getNamedType(origin: MatOrigin, tpe: MaterializedType): Option[Type with Named] =
     tpe match {
diff --git a/modules/core/src/test/scala/sangria/schema/CustomScalarSpec.scala b/modules/core/src/test/scala/sangria/schema/CustomScalarSpec.scala
index 6ba2c9a5..70889165 100644
--- a/modules/core/src/test/scala/sangria/schema/CustomScalarSpec.scala
+++ b/modules/core/src/test/scala/sangria/schema/CustomScalarSpec.scala
@@ -4,6 +4,7 @@ import java.text.SimpleDateFormat
 import java.util.Date
 
 import sangria.ast
+import sangria.macros._
 import sangria.util.Pos
 import sangria.util.SimpleGraphQlSupport._
 import sangria.validation.ValueCoercionViolation
@@ -11,6 +12,7 @@ import sangria.validation.ValueCoercionViolation
 import scala.util.{Failure, Success, Try}
 import org.scalatest.matchers.should.Matchers
 import org.scalatest.wordspec.AnyWordSpec
+import sangria.validation.BigDecimalCoercionViolation
 
 class CustomScalarSpec extends AnyWordSpec with Matchers {
   "Schema" should {
@@ -80,5 +82,48 @@ class CustomScalarSpec extends AnyWordSpec with Matchers {
             Pos(3, 28)))
       )
     }
+
+    "allow to overwrite built-in scalar type" in {
+
+      def parseBigDecimal(s: String) = Try(BigDecimal(s)) match {
+        case Success(d) => Right(d)
+        case Failure(error) => Left(BigDecimalCoercionViolation)
+      }
+
+      val BigDecimalType = ScalarType[BigDecimal](
+        "BigDecimal",
+        description = Some("A string only BigDecimal type"),
+        coerceOutput = (d, _) => d.toString,
+        coerceUserInput = {
+          case s: String => parseBigDecimal(s)
+          case _ => Left(BigDecimalCoercionViolation)
+        },
+        coerceInput = {
+          case ast.StringValue(s, _, _, _, _) => parseBigDecimal(s)
+          case _ => Left(BigDecimalCoercionViolation)
+        }
+      )
+
+      val schemaSdl = graphql"""
+        scalar BigDecimal
+
+        type Query {
+          age: BigDecimal!
+        }
+      """
+
+      val schema = Schema.buildFromAst[Unit](
+        schemaSdl,
+        AstSchemaBuilder.resolverBased(
+          ScalarResolver[Unit] { case ast.ScalarTypeDefinition("BigDecimal", _, _, _, _) =>
+            BigDecimalType
+          }
+        )
+      )
+
+      schema.scalarTypes.collectFirst { case ("BigDecimal", tpe) => tpe } should be(
+        Some(BigDecimalType))
+
+    }
   }
 }