feat(codegen): handle (v, ok) methods

codegen/field.go

@@ -25,6 +25,7 @@ type Field struct {
 	Args             []*FieldArgument // A list of arguments to be passed to this field
 	MethodHasContext bool             // If this is bound to a go method, does the method also take a context
 	NoErr            bool             // If this is bound to a go method, does that method have an error as the second argument
+	VOkFunc          bool             // If this is bound to a go method, is it of shape (interface{}, bool)
 	Object           *Object          // A link back to the parent object
 	Default          interface{}      // The default value
 	Stream           bool             // does this field return a channel?
@@ -152,6 +153,8 @@ func (b *builder) bindField(obj *Object, f *Field) (errret error) {
 		sig := target.Type().(*types.Signature)
 		if sig.Results().Len() == 1 {
 			f.NoErr = true
+		} else if s := sig.Results(); s.Len() == 2 && s.At(1).Type().String() == "bool" {
+			f.VOkFunc = true
 		} else if sig.Results().Len() != 2 {
 			return fmt.Errorf("method has wrong number of args")
 		}

codegen/field.gotpl

@@ -112,7 +112,13 @@ func (ec *executionContext) _{{$object.Name}}_{{$field.Name}}(ctx context.Contex
 			return nil, fmt.Errorf("unexpected type %T for field %s", v, {{ .Name | quote}})
 		}
 	{{- else if .IsMethod -}}
-		{{- if .NoErr -}}
+		{{- if .VOkFunc -}}
+			v, ok := {{.GoReceiverName}}.{{.GoFieldName}}({{ .CallArgs }})
+			if !ok {
+				return nil, nil
+			}
+			return v, nil
+		{{- else if .NoErr -}}
 			return {{.GoReceiverName}}.{{.GoFieldName}}({{ .CallArgs }}), nil
 		{{- else -}}
 			return {{.GoReceiverName}}.{{.GoFieldName}}({{ .CallArgs }})

codegen/testserver/resolver.go

@@ -272,6 +272,14 @@ func (r *queryResolver) OptionalUnion(ctx context.Context) (TestUnion, error) {
 	panic("not implemented")
 }
 
+func (r *queryResolver) VOkCaseValue(ctx context.Context) (*VOkCaseValue, error) {
+	panic("not implemented")
+}
+
+func (r *queryResolver) VOkCaseNil(ctx context.Context) (*VOkCaseNil, error) {
+	panic("not implemented")
+}
+
 func (r *queryResolver) ValidType(ctx context.Context) (*ValidType, error) {
 	panic("not implemented")
 }