nested fragment data returning null from cache

Hello,

I am experiencing this issue in React Native using Apollo Client: I have a query containing a fragment and in it a nested fragment; when the query runs the first time (empty cache) the result is returned correctly and I can see data inside the fragment and the nested fragment; on the following rendering, when the result returns from the cache (default fetchPolicy), data is correctly returned except the nested fragment which contains “null”. I don’t manually manipulate the cache in any way on this query and we have no inMemoryCache configuration for it or its fields.

The nested fragment does NOT have an id but I tried setting a keyField on another field and nothing changed. Removing the cache (fetchPolicy=no-cache) solves the problem but we want to use it.

Do you know what can cause the nested fragment data to be null in this situation or similar?

Here is a query example that resemble our query:

query MyData($myParam: String!) {
  getMyData(myParam: $myParam) {
    categories {
      catOne {
        ...MyFragmentOne
      }
      catTwo {
        ...MyFragmentOne
      }
      catThree {
        ...MyFragmentOne
      }
    }
    brands {
      brandOne {
        ...Brand
      }
      BrandTwo {
        ...Brand
      }
      BrandThree {
        ...Brand
      }
    }
  }
}

fragment Brand on Brand {
  id
  name
  keywords {
    ...Keywords
  }
}

fragment Keywords on Keywords {
  lang1
  lang2
}`

Keywords is the data fragment returning null from the cache,

Versions I am are experiencing this in React Native using version ‘3.3.19’, I also tested using ‘3.4’ and the latest ‘3.6.9’ with the same result.

[mrclay]

I also wasted hours before figuring out the missing possibleTypes config.

[dylanwulf]

Shot in the dark here, but have you set up the possibleTypes configuration for your schema’s unions and interfaces?

nope, no possibleTypes defined so far in this project. thanks

Ah ok. If any of those fragments use a type that implements an interface, or is part of a union, then adding possibleTypes might help. If you’re not using any unions or interfaces then I’m not sure what’s wrong.