schema transform bug: cannot return null for non nullable type subscription_root.user

[wawhal]

So we are trying to perform schema-stitching with schema transforms to prefix schema types and root-fields. This is how we do it:

const renameSchema = (schema, prefix) => {
 return transformSchema(
    schema,
    [
      new RenameTypes((type) => `${prefix}_${type}`),
      new RenameRootFields((operation, name) => `${prefix}_${name}`)
    ]
  );     
};

Without renaming, the schema stitching works totally.
After renaming, it works fine in case of queries and mutations but throws an error in case of subscriptions.

The error message reads "Cannot return null for non-nullable field subscription_root.user".

Some details:

1. Subscription root of the remote server: subscription_root
2. New subscription root: Subscription
3. Old root fields: user images
4. New root fields: hasura_user, hasura_images

You can clone this repo and run npm install && npm start from the root to see this error in action.
https://github.com/wawhal/custom-resolvers-boilerplate

[yaacovCR]

Duplicate of #997.
Fixed in #1104.

[yaacovCR]

Fixed in graphql-tools-fork https://www.npmjs.com/package/graphql-tools-fork

[kamilkisiela]

We recently released an alpha version of GraphQL Tools (#1308) that should fix the issue.

Please update graphql-tools to next or run:

npx match-version graphql-tools next

Let us know if it solves the problem, we're counting for your feedback! :)

[yaacovCR]

Rolled into #1306