[bug] The dissimilarity of fromJSON with data when using fragments over union types

[meg4cyberc4t]

I have this query:

query getStudentTask($input: GetStudentTaskInput!, $studentId: UUID) {
  getStudentTask_v2(input: $input) {
    ...TaskFragment
  }
}

fragment TaskFragment on Task {
  id
  contentBlock {
    ...TopicContentBlockFragment
  }
  answers {
    ...TaskAnswerFragment
  }
}


fragment TopicContentBlockFragment on DisciplineTopicContentBlock {
  ... on InfoDisciplineTopicContentBlock {
    body
    id
    kind
    name
    order
  }
  ... on TaskDisciplineTopicContentBlock {
    body
    id
    kind
    maxScore
    name
    order
    studentCanSendAnswers(studentId: $studentId)
    studentCanSendAnswersAfterDeadline(studentId: $studentId)
    studentDeadline(studentId: $studentId)
  }
  ... on TestDisciplineTopicContentBlock {
    body
    deadlineDate
    id
    kind
    testMaxScore: maxScore
    name
    order
    testId
    canBePassed
    canBeUpdated
    studentScore(studentId: $studentId)
    availableIntervalForStudent(studentId: $studentId) {
      from
      to
    }
  }
}

The assembly takes place without errors, scanning network requests, it is clear that everything is OK.

However, at the moment of fromJson unpacking, the following error appears:

StudentTaskBloc cathing error type 'Null' is not a subtype of type 'String' in type cast | type 'Null' is not a subtype of type 'String' in type cast
flutter: #0      new Fragment$TopicContentBlockFragment$$TaskDisciplineTopicContentBlock.fromJson (package:new_lxp_mobile/src/features/topics/data/data_sources/remote/fragments/topic_content_block_fragment.graphql.dart:894:21)
...

After conducting my own research, I find out that:

factory Query$getStudentTask.fromJson(Map<String, dynamic> json) {
    print(json);
    ...
}

sends this

flutter: {getStudentTask_v2: {id: a3ac7438-4f4e-4109-83c0-f27e8f148952, contentBlock: {__typename: TaskDisciplineTopicContentBlock}, answers: [], __typename: Task}, __typename: Query}

For all proxies, I saw that the data is being received, but at the very top of FromJSON, the part with steaming from union is lost.

[github-actions]

👋 @meg4cyberc4t
Thank you for raising an issue. I will investigate the issue and get back to you as soon as possible.
Please make sure you have provided enough context.

This library is created and maintained by me, @budde377. Please consider supporting my work and ensure our survival by donating here.

[budde377]

Thanks for reporting this! If I understand you correctly the vales from the GraphQL client does not match the network request. I suspect this might be caused by normalisation. Can you share your schema? And have you provided the possibleTypesMap to your client?