Incorrect error handling behavior

[steelbrain]

Context:

Here's what the schema looks like in this scenario:

type Query {
  viewer: Viewer
}
type Viewer {
  id: ID!
  institutions: [Institution]!
}
type Institution {
  id: ID!
  name: String!
}

We were running into a bug where ANY error in Viewer.institutions resolver would ALWAYS throw out a Error: Cannot return null for non-nullable field User.id for the GQL request which makes absolutely no sense at all.

Investigation:

Upon some rigorous digging, here's what happens:

Apollo executes the GraphQL schema -> GraphQL resolves viewer (with a wrapped resolveFn coming from this package). The wrapper calls delegateRequest, the result trace so far is correct.

Then we get to this part, transformer.transformResult converts

{
  data: { viewer: null },
  errors: [...Institution Error...]
}

into

{
  institution: ...InstitutionError...
}

This is not what the caller expects, so tries to resolve id from {institution: Error}. I think this is incorrect behavior. I'm not familiar enough with internals to suggest a proper fix except handleNull needs to handle this.

[yaacovCR]

Can you create a minimal reproduction?

Thanks!

[yaacovCR]

Is this possible related to #1047

[steelbrain]

It's likely related, I'll create a minimal reproduction tomorrow. Thanks!

[steelbrain]

Unable to repro in an isolated environment. It's possible that some of the deep dependency in production app is using an older version of graphql-tools.

Closing this until I have more information. Thank you

Edit: Update graphql-tools in all deep deps to latest version, still getting the error. Sigh. I wish it was easier to isolate this into a repro.