Polymorphic Variants capturing a Union with Fragments

[GTDev87]

Hi, I'm using "reason-apollo-client": "1.0.0-beta.0", and "@reasonml-community/graphql-ppx": "1.0.1",

and I'm having trouble interpreting unions into polymorphic variants.

Using a Js.log, I have an object which looks like the following:

{__typename: "MultipleChoiceQuestion", id: "91d7d8ec-a581-56ef-8467-ca4d54da1dd7", questionBaseId: "91d7d8ec-a581-56ef-8467-ca4d54da1dd7", questionBase: {…}, choices: Array(4)}choices: (4) [{…}, {…}, {…}, {…}]

With this graphql fragment:

module Fields = [%graphql
  {|
    fragment TestFields on Test {
      questions {
        __typename
        ...on LongAnswerQuestion {
          ...LongAnswerQuestionFields
        }
        ...on MultipleChoiceQuestion {
          ...MultipleChoiceQuestionFields
        }
        ...on TrueFalseQuestion {
          ...TrueFalseQuestionFields
        }
        ...on FillInTheBlankQuestion {
          ...FillInTheBlankQuestionFields
        }
      }
   |}
 ];

and the polymorphic variant is returning:

{__typename: "MultipleChoiceQuestion", id: "91d7d8ec-a581-56ef-8467-ca4d54da1dd7", questionBaseId: "91d7d8ec-a581-56ef-8467-ca4d54da1dd7", questionBase: {…}, choices: Array(4)}choices: (4) [{…}, {…}, {…}, {…}]
LongAnswerQuestion q
undefined

Capture through here:

  Js.log("Question_Model question");
  Js.log(question);
  switch (question) {
  | `LongAnswerQuestion(q) =>{
    Js.log("LongAnswerQuestion q");
    Js.log(q);
    q
    |> LongAnswerQuestion.Model.objectToId
    |> Schema.LongAnswerQuestion.idToString
    |> q => UnionSchema.Question.LongAnswer(q)
  }
  | `MultipleChoiceQuestion(q) =>{
    Js.log("MultipleChoiceQuestion q");
    Js.log(q);
    q
    |> MultipleChoiceQuestion.Model.objectToId
    |> Schema.MultipleChoiceQuestion.idToString
    |> q => UnionSchema.Question.MultipleChoice(q)
   }
//Where question is of type 
type unionType = [
  | `LongAnswerQuestion(LongAnswerQuestionFields.t)
  | `MultipleChoiceQuestion(MultipleChoiceQuestionFields.t)
  | `TrueFalseQuestion(TrueFalseQuestionFields.t)
  | `FillInTheBlankQuestion(FillInTheBlankQuestionFields.t)
  | `FutureAddedValue(Js.Json.t)
];
   ...

So the polymorphic variant is interpreted as the incorrect type and is returning undefined when passed through the switch statement.

Do i need a __typespec somewhere to inform the union?
Is there a working example of unions being evaluated into fragments that i can follow? I believe I had this working in 1.0.0-beta.11.

Thanks

[jfrolich]

Are you sure it's not a nullable field (and the type is not an option?). Otherwise, can you share the schema so we have a reproduction?

[GTDev87]

It's not nullable or at least is shouldn't be. questions in the fragment above is a non_null list of non_null union question types.

Even if it were null though, i find it curious that the console recognizes it as a MultipleChoiceQuestion type until it captured by the switch statement which then it gives it LongAnswerQuestion type. Also, I do look for FutureAddedValue as a case too.

I've included the file. It's very large.

graphql_schema.txt

[GTDev87]

Yea sorry if the example is very complex I was upgrading from using reasonml-community/reason-apollo-hooks#117. I'll look into making a minimal example.

After talking to @jeddeloh, I think I'm of the mind this may be because of the fact I'm defining the types in unionType myself rather than letting the ppx interpret them for me. It may be confusing the switch statement so I'm getting undefined. It is hard to unravel this because this is my design in a bigger project where I have each fragment in it's own files and i aggregate them into bigger fragments.

I'll keep digging and I'll update if I have a minimal example or if I figure out something that works.

[GTDev87]

A little more info

I expanded the query out removing the fragment directly inside the union.

module Fields = [%graphql
  {|
    fragment TestFields on Test {
      id
      questions {
        ...on LongAnswerQuestion {
          id
          questionBaseId
          questionBase {
            ...QuestionBaseFields
          }
        }
        ...on MultipleChoiceQuestion {
          id
          questionBaseId
          questionBase{
            ...QuestionBaseFields
          }
          choices{
            ...QuestionChoiceFields
          }
        }
        ...on TrueFalseQuestion {
          id
          questionBaseId
          questionBase{
            ...QuestionBaseFields
          }
          choices{
            ...QuestionChoiceFields
          }
        }
        ...on FillInTheBlankQuestion {
          id
          questionBaseId
          questionBase {
            ...QuestionBaseFields
          }
        }
      }
    }
  |}
];

I have the same issue, where the fragment are in the incorrect polymorphic variant and I am getting undefined in the object.

[GTDev87]

Turns out it was something in reason-apollo-client fixed here (jeddeloh/rescript-apollo-client@ff6ec54) I'll close.

[jfrolich]

Oh haha oops. Sorry I didn't get around looking into this!