feature: Implements specifiedBy directive

Author: NeedleInAJayStack

Sources/GraphQL/Type/Definition.swift

@@ -169,6 +169,7 @@ extension GraphQLNonNull: GraphQLWrapperType {}
 public final class GraphQLScalarType {
     public let name: String
     public let description: String?
+    public let specifiedByURL: String?
     public let kind: TypeKind = .scalar
 
     let serialize: (Any) throws -> Map
@@ -178,13 +179,15 @@ public final class GraphQLScalarType {
     public init(
         name: String,
         description: String? = nil,
+        specifiedByURL: String? = nil,
         serialize: @escaping (Any) throws -> Map,
         parseValue: ((Map) throws -> Map)? = nil,
         parseLiteral: ((Value) throws -> Map)? = nil
     ) throws {
         try assertValid(name: name)
         self.name = name
         self.description = description
+        self.specifiedByURL = specifiedByURL
         self.serialize = serialize
         self.parseValue = parseValue ?? defaultParseValue
         self.parseLiteral = parseLiteral ?? defaultParseLiteral
@@ -218,6 +221,7 @@ extension GraphQLScalarType: Encodable {
     private enum CodingKeys: String, CodingKey {
         case name
         case description
+        case specifiedByURL
         case kind
     }
 }
@@ -229,6 +233,8 @@ extension GraphQLScalarType: KeySubscriptable {
             return name
         case CodingKeys.description.rawValue:
             return description
+        case CodingKeys.specifiedByURL.rawValue:
+            return specifiedByURL
         case CodingKeys.kind.rawValue:
             return kind
         default:

Sources/GraphQL/Type/Directives.swift

@@ -123,6 +123,21 @@ public let GraphQLDeprecatedDirective = try! GraphQLDirective(
     ]
 )
 
+/**
+ * Used to provide a URL for specifying the behavior of custom scalar definitions.
+ */
+public let GraphQLSpecifiedByDirective = try! GraphQLDirective(
+    name: "specifiedBy",
+    description: "Exposes a URL that specifies the behavior of this scalar.",
+    locations: [.scalar],
+    args: [
+        "url": GraphQLArgument(
+            type: GraphQLNonNull(GraphQLString),
+            description: "The URL that specifies the behavior of this scalar."
+        ),
+    ]
+)
+
 /**
  * Used to indicate an Input Object is a OneOf Input Object.
  */
@@ -140,5 +155,6 @@ let specifiedDirectives: [GraphQLDirective] = [
     GraphQLIncludeDirective,
     GraphQLSkipDirective,
     GraphQLDeprecatedDirective,
+    GraphQLSpecifiedByDirective,
     GraphQLOneOfDirective,
 ]

Sources/GraphQL/Type/Introspection.swift

@@ -185,7 +185,7 @@ let __Type: GraphQLObjectType = try! GraphQLObjectType(
         "many kinds of types in GraphQL as represented by the `__TypeKind` enum." +
         "\n\nDepending on the kind of a type, certain fields describe " +
         "information about that type. Scalar types provide no information " +
-        "beyond a name and description, while Enum types provide their values. " +
+        "beyond a name and description and optional `specifiedByURL`, while Enum types provide their values. " +
         "Object and Interface types provide the fields they describe. Abstract " +
         "types, Union and Interface, provide the Object types possible " +
         "at runtime. List and NonNull types compose other types.",
@@ -217,6 +217,7 @@ let __Type: GraphQLObjectType = try! GraphQLObjectType(
         ),
         "name": GraphQLField(type: GraphQLString),
         "description": GraphQLField(type: GraphQLString),
+        "specifiedByURL": GraphQLField(type: GraphQLString),
         "fields": GraphQLField(
             type: GraphQLList(GraphQLNonNull(__Field)),
             args: [