GraphQL playground returns data, while app returns null

Question

I am working on an app in React+TS/GraphQL/Prisma. The API is written in GraphQL and when I run a particular query in the playground, I get the data I expect, but when I run the exact same query in react, I get null . Why would this be?

What I run in query (relevant portion)

query {
  session {
    userData: {
      firstName
      lastName
      dateOfBirth 
    }
  }
}

and in the playground it returns

{
  "data": {
    "session": {
      "userData": {
        "firstName":"John",
        "lastName":"Doe",
        "dateOfBirth":null,
      }
    }
  }
}

but in the App, when I console log the userData or data.session it returns null for the whole object. console.log(data) prints

session: {
  userData: null
}

does anyone have any ideas why this would be? The playground accurately pulls user data and populates the subfields, but on the App in the browser, it only returns "null".

Answer 1

I discovered the solution and wanted to share it here.

The problem came because we are working on a session with data that updates. So user creates a session, then updates, then the next step updates some more, etc before finally submitting the session.

The problem described in my question is based on Apollo defaulting to cache-first as it's fetch policy. So when the user updates, the next step queries the non-updated, cached version of the session data.

To fix this, at each step in the process, we need to call our query and set the fetch policy to "network-only" like so:

const {loading, error, data} = useSessionQuery({fetchPolicy: 'network-only'});

This will ensure that data is pulled from the network where your updateMutation was performed instead of the cached (outdated) copy.