1package validator
 2
 3import (
 4	"github.com/vektah/gqlparser/ast"
 5	. "github.com/vektah/gqlparser/validator"
 6)
 7
 8func init() {
 9	AddRule("UniqueVariableNames", func(observers *Events, addError AddErrFunc) {
10		observers.OnOperation(func(walker *Walker, operation *ast.OperationDefinition) {
11			seen := map[string]bool{}
12			for _, def := range operation.VariableDefinitions {
13				if seen[def.Variable] {
14					addError(
15						Message(`There can be only one variable named "%s".`, def.Variable),
16						At(def.Position),
17					)
18				}
19				seen[def.Variable] = true
20			}
21		})
22	})
23}