Defer: client expectations on subsequent payloads’ path

[BoD]

Hi!

Given this schema:

type Query {
  product(id: ID!): Product
}

type Product {
  id: ID!
  description: String
}

This query:

query ProductById {
  product(id: "0") {
    id
    ... on Product @defer {
      description
    }
  }
}

could return:

Payload 1

{
  "data": {
    "product": {
      "id": "0"
    }
  },
  "hasNext": true
}

Payload 2

{
  "data": {
    "label": "Product 0"
  },
  "path": [ "product" ],
  "hasNext": false
}

But could the response be of this form:

Payload 1

same as above

Payload 2

{
  "data": {
    "product": {
      "label": "Product 0"
    }
  },
  "hasNext": false
}

?

In other words, should subsequent payloads always be rooted at the path where the related @defer directive is applied (example 1)? Or is it also possible for them to be rooted above it (example 2)?

[glasser]

I'm reasonably sure based on my understanding of the spec that only the first version is correct — but I think the spec should have some more examples/clarity to be explicit that subsequent payloads are always "here's a subtree with the place to splice it in" and not "here's some more tree, rooted at the top, to be merged in".

[robrichard]

Yes, this is correct. I'll make sure this is noted in the spec text.

[robrichard]

I added the following wording to the response section of the spec

defer:

The path segments must point to the location of the result of the field containing the associated @defer directive.

stream:

All but the non-final path segments must
refer to the location of the list field containing the corresponding @stream
directive. The final segment of the path list must be a 0-indexed integer. This
integer indicates that this result is set at a range, where the beginning of the
range is at the index of this integer, and the length of the range is the length
of the data.

[glasser]

Or to be clear, there actually is merging still, but a single level (ie, data doesn't replace the entire node at path, which would remove the id above, but it adds all of its fields there)