Order of returned types from a subschema

[ahhhkah]

Hello,

We utilize directive-based stitching in our application, which performs well. The gateway effectively discovers and reloads subschemas, and fetches all required data as expected. However, we've noticed that in the response, the fetched types are not merged correctly.

Consider the following example:

query meals {
    meals(ids: ["123456"]) {
        id
        recipe {
            id
            name
            recipeEntries {
                amount
                unit
                product {
                    id
                    supplier
                }
            }
        }
    }
}

The product is stitched from the recipe-subschema:

type Product {
    id: ID!
}

And the products-subschema:

type Query {
    _products(ids: [ID!]!): [Product]! @merge(keyField: "id", keyArg: "ids")
    _sdl: String!
}

type Product @key(selectionSet: "{ id }") {
    id: ID!
    supplier: Supplier!
}

The merged result contains all products, but they are incorrectly merged into the RecipeEntry. For instance, we expect 140g of Chicken, but it ends up being merged into the RecipeEntry with 20g.

We found a temporary fix: sorting the result of _products in the order of received ids. Meaning if _products receives IDs in the sequence 1, 2, 3, and we return the resulting products in the same order (1, 2, 3), everything works fine. If we return the products unordered, then the merging is incorrect.

We're wondering if this ordering is actually required (as we could not find this in any specification) or if there is any other problem with our code. We expected the merging to be based on the ID and not the order.

Thank you in advance.

[ahhhkah]

Sorry, we just forgot to add some @key directives to our types.

In the example above (recipes-subschema):

type Product @key(selectionSet: "{ id }"){
    id: ID!
}