fix(gatsby): Add early return in link resolver for empty arrays

[sidharthachatterjee]

Why

Consider a schema like,

type Item {
  name: String
}

type Collection {
  items: [Item]! @link(by: "id", from: "items___NODE")
}

And a query like,

allCollection {
  nodes {
    items {
      name
    }
  }
}

If a collection has no items, this currently returns items set to null as opposed to [] (even if it is non nullable as shown in the schema above).

Why

This happens because the link resolver sets the { in: value } operator in case the field value is an array. This however doesn't make sense for an empty array.

This PR adds an early return to fix this 🙂

Todo

• I'd like to add a test for this but unsure where a test for this should go?

Related issues

@Simply007 discovered this issue when building gatsby-source-kentico. You can find a reproduction at https://github.com/Simply007/gatsby-null-instead-of-array

[sidharthachatterjee]

Published in [email protected]