I have the following code: ```object HelloWorldQueryHandler { fun hello(yourname: String) = "Hello...

# http4k

[Arnab]

I have the following code:

object HelloWorldQueryHandler {
  fun hello(yourname: String) = "Hello $yourname"
}

class GraphQLHandler: GraphQLHandler {
  private val graphql = newGraphQL(
    toSchema(
      SchemaGeneratorConfig(supportedPackages = listOf("no.example.capgemini")),
      listOf(TopLevelObject(HelloWorldQueryHandler))
    )
  ).build()

  override fun invoke(request: GraphQLRequest): GraphQLResponse =
    GraphQLResponse.from(
      graphql.execute {
        Builder()
          .query(request.query)
          .variables(request.variables)
      }
    )
}

fun main() {
  val app = routes("/graphql" bind graphQL(GraphQLHandler()))
  app.asServer(Netty()).start()
}

Now, this works when I use the GraphQL playground, but not when I use the Graphiql client. For the Graphiql client, this just returns an empty response. Am I missing something? Why is there a difference?

[dave]

suggest that you put a debugging filter on the handler handler.debug() and sniff what the difference in request is

[Arnab]

@dave: where exactly do you mean? I don’t quite understand where the handler object is 😮

[dave]

app.debug().asServer(Netty()).start()

[Arnab]

***** REQUEST: POST: /graphql *****
POST /graphql HTTP/1.1
Host: localhost:8000
Connection: keep-alive
accept: */*
Origin: null
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_16_0) AppleWebKit/537.36 (KHTML, like Gecko) GraphQLPlayground/1.8.10 Chrome/61.0.3163.100 Electron/2.0.11 Safari/537.36
content-type: application/json
Accept-Encoding: gzip, deflate
Accept-Language: en-GB
content-length: 84

<<stream>>
***** RESPONSE 200 to POST: /graphql *****
HTTP/1.1 200 OK
content-type: application/json; charset=utf-8

{"data":{"hello":"Hello arnab"},"errors":null}
***** REQUEST: POST: /graphql *****
POST /graphql HTTP/1.1
Content-Type: application/json
User-Agent: graphiql-app
Host: localhost:8000
Connection: close
content-length: 65

<<stream>>
***** RESPONSE 400 to POST: /graphql *****
HTTP/1.1 400 Bad Request

[Arnab]

What in the world…?

[dave]

put debug(debugStreams=true) instead. you'll get the content of the request

[Arnab]

So this: {"query":"{\n hello(yourname:\"Arnab\")\n}","variables":null} gives 400, but this does not {"operationName":null,"variables":{},"query":"{\n hello(yourname: \"arnab\")\n}\n"} I am really not sure what’s going on here. The first one is from Graphiql and the other from GraphQL playground.

[Arnab]

In my eyes both are identical except playground sends an empty dict for variables and null for operation name

[Arnab]

Apparently sending an empty dict in GraphiQL is the thing 😮 This is really strange

[dave]

I think the problem is that at the moment the vraiables can't be null

data class GraphQLRequest(val query: String = "",
                          val operationName: String? = null,
                          val variables: Map<String, Any> = emptyMap()) {
    companion object {
        val requestLens = Body.auto<GraphQLRequest>().toLens()
    }
}

[dave]

interestingly - the graphql java lib will blow up if it is null:

this.variables = assertNotNull(variables, () -> "variables map can't be null");

[dave]

we can easily fix it, but I'm not sure what the actual spec says about if the fields are nullable

[Arnab]

Well, I took a look at the specs, and as far as I can see here, variables are not required in a query. Nullability. I cannot say anything about however:
https://spec.graphql.org/June2018/#sec-Validation

What I can say however, is that apollo graphql for instance, has nullable variables:
https://github.com/apollographql/apollo-client/blob/cbcf951256b22553bdb065dfa0d32c0a4ca804d3/src/react/hooks/useQuery.ts

[dave]

no problem - we can fix it to not blow up in the absence of variables

[Arnab]

Where is this code from?

this.variables = assertNotNull(variables, () -> "variables map can't be null");

[Arnab]

(the snippet you posted above)

[dave]

that's from graphql-java library

[Arnab]

This is interesting. I’ll take a look as to how ktor solves this for instance.

[dave]

well it's just a matter of making the field nullable and passing in an empty map instead. it's already fixed

[Arnab]

Oh ok, is the release already out?

[dave]

not yet

[dave]

it's out now 🙂