API for setting custom directives

Prototype for #913
In this prototype, we check how we can apply custom directives much easier.
Furthermore, we check if we can prove type safety, to that a custom directive
that can be applied on some elements cannot be applied on others.

Limitations:
- a directive can be applied on a field definition for example. With that current approach,
we cannot formulate that with the type system as a field definition lives in sangria.ast, and
we only handle sangria.schema types.
- we are introducing new types to mark on which elements a directive can be applied. Those types
are kind of duplication of the current [sangria.schema.DirectiveLocation values](https://github.com/sangria-graphql/sangria/blob/f339b5df97bd89c2a24fcfc977a1f20191ffd7fc/modules/core/src/main/scala/sangria/schema/Schema.scala#L1136-L1158).

Author: yanns

build.sbt

@@ -126,7 +126,10 @@ lazy val core = project
       ProblemFilters.exclude[MissingTypesProblem]("sangria.schema.Directive$"),
       ProblemFilters.exclude[MissingTypesProblem]("sangria.schema.MappedAbstractType"),
       ProblemFilters.exclude[IncompatibleMethTypeProblem](
-        "sangria.execution.Resolver.resolveSimpleListValue")
+        "sangria.execution.Resolver.resolveSimpleListValue"),
+      ProblemFilters.exclude[DirectMissingMethodProblem]("sangria.schema.Argument.apply"),
+      ProblemFilters.exclude[DirectMissingMethodProblem]("sangria.schema.Field.subs"),
+      ProblemFilters.exclude[DirectMissingMethodProblem]("sangria.schema.Field.apply")
     ),
     Test / testOptions += Tests.Argument(TestFrameworks.ScalaTest, "-oF"),
     libraryDependencies ++= Seq(

modules/ast/src/main/scala/sangria/ast/QueryAst.scala

@@ -325,7 +325,7 @@ sealed trait WithDirectives extends AstNode {
 
 case class Directive(
     name: String,
-    arguments: Vector[Argument],
+    arguments: Vector[Argument] = Vector.empty,
     comments: Vector[Comment] = Vector.empty,
     location: Option[AstLocation] = None)
     extends AstNode

modules/core/src/main/scala/sangria/schema/AstSchemaBuilder.scala

@@ -324,8 +324,8 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
       description = definition.flatMap(_.description.map(_.value)),
       directives = directives,
       astDirectives =
-        definition.fold(Vector.empty[ast.Directive])(_.directives) ++ extensions.flatMap(
-          _.directives),
+        (definition.fold(Vector.empty[ast.Directive])(_.directives) ++ extensions.flatMap(
+          _.directives)).asInstanceOf[Vector[ast.Directive with OnSchema]],
       astNodes = Vector(mat.document) ++ extensions ++ definition.toVector
     )
 
@@ -346,7 +346,8 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
       directives = directives,
       description = originalSchema.description,
       validationRules = originalSchema.validationRules,
-      astDirectives = originalSchema.astDirectives ++ extensions.flatMap(_.directives),
+      astDirectives = (originalSchema.astDirectives ++ extensions.flatMap(_.directives))
+        .asInstanceOf[Vector[ast.Directive with OnSchema]],
       astNodes = {
         val (docs, other) = originalSchema.astNodes.partition(_.isInstanceOf[ast.Document])
         val newDoc = ast.Document.merge(docs.asInstanceOf[Vector[ast.Document]] :+ mat.document)
@@ -374,7 +375,7 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
             interfaces = interfaces,
             instanceCheck =
               (value: Any, clazz: Class[_], _: ObjectType[Ctx, Any]) => fn(value, clazz),
-            astDirectives = directives,
+            astDirectives = directives.asInstanceOf[Vector[ast.Directive with OnObject]],
             astNodes = (definition +: extensions).toVector
           )
         case None =>
@@ -384,7 +385,7 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
             fieldsFn = fields,
             interfaces = interfaces,
             instanceCheck = ObjectType.defaultInstanceCheck[Ctx, Any],
-            astDirectives = directives,
+            astDirectives = directives.asInstanceOf[Vector[ast.Directive with OnObject]],
             astNodes = (definition +: extensions).toVector
           )
       }
@@ -404,15 +405,17 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
         existing.copy(
           fieldsFn = fields,
           interfaces = interfaces,
-          astDirectives = existing.astDirectives ++ extensions.flatMap(_.directives),
+          astDirectives = existing.astDirectives ++ extensions.flatMap(
+            _.directives.asInstanceOf[Vector[ast.Directive with OnObject]]),
           astNodes = existing.astNodes ++ extensions,
           instanceCheck = (value: Any, clazz: Class[_], _: ObjectType[Ctx, Any]) => fn(value, clazz)
         )(ClassTag(existing.valClass))
       case None =>
         existing.copy(
           fieldsFn = fields,
           interfaces = interfaces,
-          astDirectives = existing.astDirectives ++ extensions.flatMap(_.directives),
+          astDirectives = existing.astDirectives ++ extensions.flatMap(
+            _.directives.asInstanceOf[Vector[ast.Directive with OnObject]]),
           astNodes = existing.astNodes ++ extensions,
           instanceCheck =
             existing.instanceCheck.asInstanceOf[(Any, Class[_], ObjectType[Ctx, _]) => Boolean]
@@ -430,7 +433,8 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
         name = typeName(definition),
         description = typeDescription(definition),
         fieldsFn = fields,
-        astDirectives = definition.directives ++ extensions.flatMap(_.directives),
+        astDirectives = (definition.directives ++ extensions.flatMap(_.directives))
+          .asInstanceOf[Vector[ast.Directive with OnInputObjectType]],
         astNodes = definition +: extensions
       ))
 
@@ -449,7 +453,7 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
         fieldsFn = fields,
         interfaces = Nil,
         manualPossibleTypes = () => Nil,
-        astDirectives = directives,
+        astDirectives = directives.asInstanceOf[Vector[ast.Directive with OnInterface]],
         astNodes = (definition +: extensions).toVector
       ))
   }
@@ -464,7 +468,8 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
       fieldsFn = fields,
       manualPossibleTypes = () => Nil,
       interfaces = Nil,
-      astDirectives = existing.astDirectives ++ extensions.flatMap(_.directives),
+      astDirectives = (existing.astDirectives ++ extensions
+        .flatMap(_.directives)).asInstanceOf[Vector[ast.Directive with OnInterface]],
       astNodes = existing.astNodes ++ extensions
     )
 
@@ -479,7 +484,8 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
         name = typeName(definition),
         description = typeDescription(definition),
         types = types,
-        astDirectives = definition.directives ++ extensions.flatMap(_.directives),
+        astDirectives = (definition.directives ++ extensions.flatMap(_.directives))
+          .asInstanceOf[Vector[ast.Directive with OnUnion]],
         astNodes = definition +: extensions
       ))
 
@@ -491,8 +497,10 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
       mat: AstSchemaMaterializer[Ctx]): UnionType[Ctx] =
     existing.copy(
       typesFn = () => types,
-      astDirectives = existing.astDirectives ++ extensions.flatMap(_.directives),
-      astNodes = existing.astNodes ++ extensions)
+      astDirectives = (existing.astDirectives ++ extensions.flatMap(_.directives))
+        .asInstanceOf[Vector[ast.Directive with OnUnion]],
+      astNodes = existing.astNodes ++ extensions
+    )
 
   def extendScalarAlias[T, ST](
       origin: MatOrigin,
@@ -516,7 +524,8 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
         coerceInput = scalarCoerceInput(definition),
         complexity = scalarComplexity(definition),
         scalarInfo = scalarValueInfo(definition),
-        astDirectives = definition.directives ++ extensions.flatMap(_.directives),
+        astDirectives = (definition.directives ++ extensions.flatMap(_.directives))
+          .asInstanceOf[Vector[ast.Directive with OnScalar]],
         astNodes = definition +: extensions
       ))
 
@@ -531,7 +540,8 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
         name = typeName(definition),
         description = typeDescription(definition),
         values = values,
-        astDirectives = definition.directives ++ extensions.flatMap(_.directives),
+        astDirectives = (definition.directives ++ extensions.flatMap(_.directives))
+          .asInstanceOf[Vector[ast.Directive with OnEnumType]],
         astNodes = definition +: extensions
       ))
 
@@ -547,7 +557,7 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
         description = enumValueDescription(definition),
         value = enumValue(typeDefinition, definition),
         deprecationReason = enumValueDeprecationReason(definition),
-        astDirectives = definition.directives,
+        astDirectives = definition.directives.asInstanceOf[Vector[ast.Directive with OnEnumValue]],
         astNodes = Vector(definition)
       ))
 
@@ -570,7 +580,7 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
         deprecationReason = fieldDeprecationReason(definition),
         complexity = fieldComplexity(typeDefinition, definition),
         manualPossibleTypes = () => Nil,
-        astDirectives = definition.directives,
+        astDirectives = definition.directives.asInstanceOf[Vector[ast.Directive with OnField]],
         astNodes = Vector(definition)
       ))
 
@@ -655,7 +665,7 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
         description = inputFieldDescription(definition),
         fieldType = tpe,
         defaultValue = defaultValue,
-        astDirectives = definition.directives,
+        astDirectives = definition.directives.asInstanceOf[Vector[ast.Directive with OnInputField]],
         astNodes = Vector(definition)
       ))
 
@@ -683,7 +693,7 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
         argumentType = tpe,
         defaultValue = defaultValue,
         fromInput = argumentFromInput(typeDefinition, fieldDefinition, definition),
-        astDirectives = definition.directives,
+        astDirectives = definition.directives.asInstanceOf[Vector[ast.Directive with OnArgument]],
         astNodes = Vector(definition)
       ))
 
@@ -720,8 +730,10 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
       mat: AstSchemaMaterializer[Ctx]): InputObjectType[T] =
     existing.copy(
       fieldsFn = fields,
-      astDirectives = existing.astDirectives ++ extensions.flatMap(_.directives),
-      astNodes = existing.astNodes ++ extensions)
+      astDirectives = (existing.astDirectives ++ extensions.flatMap(_.directives))
+        .asInstanceOf[Vector[ast.Directive with OnInputObjectType]],
+      astNodes = existing.astNodes ++ extensions
+    )
 
   def transformEnumType[T](
       origin: MatOrigin,
@@ -731,7 +743,9 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
     val dirs = existing.astDirectives ++ extensions.flatMap(_.directives)
 
     if (dirs.nonEmpty)
-      existing.copy(astDirectives = dirs, astNodes = existing.astNodes ++ extensions)
+      existing.copy(
+        astDirectives = dirs.asInstanceOf[Vector[ast.Directive with OnEnumType]],
+        astNodes = existing.astNodes ++ extensions)
     else existing
   }
 
@@ -743,7 +757,9 @@ class DefaultAstSchemaBuilder[Ctx] extends AstSchemaBuilder[Ctx] {
     val dirs = existing.astDirectives ++ extensions.flatMap(_.directives)
 
     if (dirs.nonEmpty)
-      existing.copy(astDirectives = dirs, astNodes = existing.astNodes ++ extensions)
+      existing.copy(
+        astDirectives = dirs.asInstanceOf[Vector[ast.Directive with OnScalar]],
+        astNodes = existing.astNodes ++ extensions)
     else existing
   }
 

modules/core/src/main/scala/sangria/schema/AstSchemaMaterializer.scala

@@ -703,7 +703,8 @@ class AstSchemaMaterializer[Ctx] private (
   def extendEnumType(origin: MatOrigin, tpe: EnumType[_]) = {
     val extensions = findEnumExtensions(tpe.name)
     val extraValues = extensions.flatMap(_.values)
-    val extraDirs = extensions.flatMap(_.directives)
+    val extraDirs =
+      extensions.flatMap(_.directives).asInstanceOf[Vector[ast.Directive with OnEnumType]]
 
     val ev = extraValues.flatMap(buildEnumValue(origin, Right(tpe), _, extensions))
 

modules/core/src/main/scala/sangria/schema/ResolverBasedAstSchemaBuilder.scala

@@ -149,8 +149,8 @@ class ResolverBasedAstSchemaBuilder[Ctx](val resolvers: Seq[AstSchemaResolver[Ct
       description = definition.flatMap(_.description.map(_.value)),
       directives = directives,
       astDirectives =
-        definition.fold(Vector.empty[ast.Directive])(_.directives) ++ extensions.flatMap(
-          _.directives),
+        (definition.fold(Vector.empty[ast.Directive])(_.directives) ++ extensions.flatMap(
+          _.directives)).asInstanceOf[Vector[ast.Directive with OnSchema]],
       astNodes = Vector(mat.document) ++ extensions ++ definition.toVector,
       validationRules = SchemaValidationRule.default :+ new ResolvedDirectiveValidationRule(
         this.directives.filterNot(_.repeatable).map(_.name).toSet)