specify the path instead of creating a deferred response from the root

[Geal]

on this query:

query ProductById {
  product(id: "apollo-federation") {
    id
    ... on ProductItf @defer {
      package
    }
  }
}

we get:

{
  "data": {
    "product": {
      "id": "apollo-federation"
    }
  },
  "hasNext": true
}

then:

{
  "data": {
    "product": {
      "package": "@apollo/federation"
    }
  },
  "hasNext": true
}

while the second response should be:

{
  "data": {
    "package": "@apollo/federation"
  },
  "path": [ "product" ],
  "hasNext": true
}

[BoD]

An example with lists.

Query

query AllProducts {
  allProducts {
    id
    ... on Product @defer {
      hidden
    }
  }
}

Router current behavior

{"data":{"allProducts":[{"id":"apollo-federation"},{"id":"apollo-studio"}]},"hasNext":true}
{"data":{"allProducts":[{},{}]},"hasNext":true}
{"hasNext":false}

What we would expect

{"data":{"allProducts":[{"id":"apollo-federation"},{"id":"apollo-studio"}]},"hasNext":true}
{"data":{"hidden":null},"path":["allProducts",0],"hasNext":true}
{"data":{"hidden":null},"path":["allProducts",1],"hasNext":false}

We never expect to have to merge lists, instead we expect each item to have its own payload. This allows the client to know at each payload what has been received or not.

[Geal]

that one with lists is unlikely to happen, considering how the query plan is built. And the separate {"hasNext":false} is necessary because there's no reliable way to know when a deferred response is the last one

[BoD]

The separate {"hasNext":false} is not an issue on our side 👍

For the lists: to clarify, on our side, the need is to have a 1:1 mapping between payloads and deferred fragments.

[alessbell]

The separate {"hasNext":false} is also not an issue on our side. We would, however, also expect each item in a list to have its own payload.

Given graphql/defer-stream-wg#46, can we consider this question similarly resolved?

[Geal]

ok so #1529 should fix it, and the good news is that after thinking about this for a while, the only correct way I see to implement it solves both points at once, using a path prefix and generating one response per list element

[Geal]

@BoD @alessbell this will go in the next release, probably early next week

[BoD]

very cool! 🙏

[BoD]

Tested with v0.16.0, it's looking good on Apollo Kotlin's side! 🎉

[Geal]

Nice 😄