fix for #124 is incomplete

What happened

The com.netflix.graphql.dgs.client.codegen.InputValueSerializer from com.netflix.graphql.dgs.codegen:graphql-dgs-codegen-client-core:5.1.16 did not emit a GraphQL compliant string literal causing the server to which the request was sent to error while trying to parse the GraphQL query

How to reproduce it

1. Create a schema1.graphqls as below
2. Use the codegen plugin with generateClient = true
3. Create a driver class as show below
4. Observe the parse error when parsing the return from .serialize

I have a failing test, too, although it was just some "hello world" failures, and does not attempt to enumerate all of the missing edge cases

Samples

schema1.graphqls

input PersonInput {
  name: String
}
type Person {
    name: String
}
type Query {
    friends(like: PersonInput): Person
}

Driver.java

package com.example;

import com.example.gql.client.FriendsGraphQLQuery;
import com.example.gql.client.FriendsProjectionRoot;
import com.example.gql.types.PersonInput;
import com.netflix.graphql.dgs.client.codegen.GraphQLQueryRequest;
import graphql.parser.Parser;

public class Driver {
    public static void main(String[] args) {
        final var names = new String[] {
                // but unicode is already correct
                "💣",
                "\r\n",
                "\u0000",
                "\u001F",
        };
        for (var name : names) {
            final String gql = new GraphQLQueryRequest(
                    FriendsGraphQLQuery.newRequest()
                            .like(PersonInput.newBuilder()
                                    .name(name)
                                    .build())
                            .build(),
                    new FriendsProjectionRoot().name()
            ).serialize();
            System.out.printf("gql = <<%s>>%n", gql);
            var doc = Parser.parse(gql);
            System.out.println("doc = " + doc);
        }
    }
}

What was expected

GraphQLQueryRequest.serialize should return legal GraphQL query text

Versions

• id("com.netflix.dgs.codegen") version "5.1.16"
• implementation("com.netflix.graphql.dgs:graphql-dgs-client:4.9.16")

Workaround

In case someone else stumbles upon this issue, I have a work-around until it is fixed: supersede the scalars parameter and register a JSON-safe graphql.scalar.GraphqlStringCoercing:

            final Map<Class<?>, Coercing<?, ?>> scalars = Map.of(String.class, new GraphqlStringCoercing() {
                @Override
                public String serialize(final Object input) {
                    final var s = (String) input;
                    // this one was chosen because dgs-client uses it, 
                    // meaning it will be present everywhere GraphQLQueryRequest is
                    return net.minidev.json.JSONValue.escape(s);
                }
            });
            final String gql = new GraphQLQueryRequest(
                    FriendsGraphQLQuery.newRequest()
                            .like(PersonInput.newBuilder()
                                    .name(name)
                                    .build())
                            .build(),
                    new FriendsProjectionRoot().name(),
                    scalars
            ).serialize();
            // and now gql will parse successfully

Start with com.netflix.graphql.dgs.client.codegen.InputValueSerializer and GraphQLQueryRequest.serialize, then review the linked failing test commit and the GraphQL October 2021 string-literal rules. Reproduce the examples containing carriage returns, null, and control characters with the client codegen setup. Done means serialized queries parse successfully for these cases and the relevant tests cover the escaping behavior.