1package validator
 2
 3import (
 4	"strconv"
 5
 6	"github.com/vektah/gqlparser/ast"
 7	. "github.com/vektah/gqlparser/validator"
 8)
 9
10func init() {
11	AddRule("SingleFieldSubscriptions", func(observers *Events, addError AddErrFunc) {
12		observers.OnOperation(func(walker *Walker, operation *ast.OperationDefinition) {
13			if operation.Operation != ast.Subscription {
14				return
15			}
16
17			if len(operation.SelectionSet) > 1 {
18				name := "Anonymous Subscription"
19				if operation.Name != "" {
20					name = `Subscription ` + strconv.Quote(operation.Name)
21				}
22
23				addError(
24					Message(`%s must select only one top level field.`, name),
25					At(operation.SelectionSet[1].GetPosition()),
26				)
27			}
28		})
29	})
30}