Parse error - Syntax Error GraphQL (57:49) Unexpected Name "null"

[StarpTech]

I faced this error during the benchmark of GraphQL parsers in the wild.

Query: https://github.com/StarpTech/graphql-parser-bench/blob/main/kitchen-sink.graphql Code: https://github.com/StarpTech/graphql-parser-bench/tree/main/go-graphql

2021/08/15 11:19:12 Syntax Error GraphQL (57:49) Unexpected Name "null"

56: {
57:   unnamed(truthy: true, falsey: false, nullish: null),
                                                    ^
58:   query

[chrisfrank]

I ran into this issue today when trying to write a mutation that allows clearing a nullable field. Here's an inline example that reproduces the problem. If a PR would be welcome, I'd be happy to try to open one with a fix. I think we can also work around this by agreeing on some sentinel value to treat as null, if that's what you'd advise. Thanks!

package main

import (
	"fmt"
	"log"

	"github.com/graphql-go/graphql"
)

func main() {
	var config graphql.SchemaConfig
	config.Query = graphql.NewObject(graphql.ObjectConfig{
		Name:   "Query",
		Fields: graphql.Fields{},
	})
	config.Mutation = graphql.NewObject(graphql.ObjectConfig{
		Name: "Mutation",
		Fields: graphql.Fields{
			"put": &graphql.Field{
				Args: graphql.FieldConfigArgument{
					"value": &graphql.ArgumentConfig{
						Type: graphql.String,
					},
				},
				Type: graphql.NewObject(graphql.ObjectConfig{
					Name: "result",
					Fields: graphql.Fields{
						"value": &graphql.Field{Type: graphql.String},
					},
				}),
				Resolve: func(p graphql.ResolveParams) (any, error) {
					val := p.Args["value"]
					return fmt.Sprintf("%v", val), nil
				},
			},
		},
	})
	schema, _ := graphql.NewSchema(config)

	for _, request := range []string{
		`mutation { put(value: "hello"){ value } }`,
		`mutation { put(value: ""){ value } }`,
		`mutation { put(value: null ){ value } }`,
	} {
		result := graphql.Do(graphql.Params{
			Schema:        schema,
			RequestString: request,
		})
		if result.HasErrors() {
			log.Fatalf("query %s has errors %v", request, result.Errors)
		}
	}
}