support for cyclic fields on defintion

definition.go

@@ -398,6 +398,7 @@ type ObjectConfig struct {
 	IsTypeOf    IsTypeOfFn  `json:"isTypeOf"`
 	Description string      `json:"description"`
 }
+
 type FieldsThunk func() Fields
 
 func NewObject(config ObjectConfig) *Object {
@@ -506,19 +507,26 @@ func defineInterfaces(ttype *Object, interfaces []*Interface) ([]*Interface, err
 	return ifaces, nil
 }
 
-func defineFieldMap(ttype Named, fields Fields) (FieldDefinitionMap, error) {
+func defineFieldMap(ttype Named, fields interface{}) (FieldDefinitionMap, error) {
+	var fieldMap Fields
+	switch fields.(type) {
+	case Fields:
+		fieldMap = fields.(Fields)
+	case FieldsThunk:
+		fieldMap = fields.(FieldsThunk)()
+	}
 
 	resultFieldMap := FieldDefinitionMap{}
 
 	err := invariant(
-		len(fields) > 0,
+		len(fieldMap) > 0,
 		fmt.Sprintf(`%v fields must be an object with field names as keys or a function which return such an object.`, ttype),
 	)
 	if err != nil {
 		return resultFieldMap, err
 	}
 
-	for fieldName, field := range fields {
+	for fieldName, field := range fieldMap {
 		if field == nil {
 			continue
 		}
@@ -1080,8 +1088,8 @@ type InputObject struct {
 
 	typeConfig InputObjectConfig
 	fields     InputObjectFieldMap
-
-	err error
+	init       bool
+	err        error
 }
 type InputObjectFieldConfig struct {
 	Type         Input       `json:"type"`
@@ -1129,7 +1137,7 @@ func NewInputObject(config InputObjectConfig) *InputObject {
 	gt.PrivateName = config.Name
 	gt.PrivateDescription = config.Description
 	gt.typeConfig = config
-	gt.fields = gt.defineFieldMap()
+	//gt.fields = gt.defineFieldMap()
 	return gt
 }
 
@@ -1175,9 +1183,14 @@ func (gt *InputObject) defineFieldMap() InputObjectFieldMap {
 		field.DefaultValue = fieldConfig.DefaultValue
 		resultFieldMap[fieldName] = field
 	}
+	gt.init = true
 	return resultFieldMap
 }
+
 func (gt *InputObject) Fields() InputObjectFieldMap {
+	if !gt.init {
+		gt.fields = gt.defineFieldMap()
+	}
 	return gt.fields
 }
 func (gt *InputObject) Name() string {

definition_test.go

@@ -619,3 +619,25 @@ func TestTypeSystem_DefinitionExample_IncludesFieldsThunk(t *testing.T) {
 		t.Fatalf("Unexpected result, Diff: %v", testutil.Diff(fieldMap["s"].Type, someObject))
 	}
 }
+
+func TestTypeSystem_DefinitionExampe_AllowsCyclicFieldTypes(t *testing.T) {
+	personType := graphql.NewObject(graphql.ObjectConfig{
+		Name: "Person",
+		Fields: (graphql.FieldsThunk)(func() graphql.Fields {
+			return graphql.Fields{
+				"name": &graphql.Field{
+					Type: graphql.String,
+				},
+				"bestFriend": &graphql.Field{
+					Type: personType,
+				},
+			}
+		}),
+	})
+
+	fieldMap := personType.Fields()
+	if !reflect.DeepEqual(fieldMap["name"].Type, graphql.String) {
+		t.Fatalf("Unexpected result, Diff: %v", testutil.Diff(fieldMap["bestFriend"].Type, personType))
+	}
+
+}