@requires directive not found in gateway list of directives

[aleccool213]

Hi!

My team writes the gateway schema to disk for a number of reasons. We like seeing what our federated graph schema compiles to and its nice for communicating what the schema looks like to other teams (we dont use a schema registry).

We recently started to use the @requires directive in a service and the gateway doesn't list it in the directives available. Because of this, @requires does not get defined at the top of the schema file even though its being used in the schema. This breaks our linting and also doesn't follow the GraphQL schema spec closely.

Functionally @requires works as expected for the federated services.

Steps to reproduce

1. Create a new node project on your computer.

2. Copy and paste the example gateway code from the repo into a index.js file.

3. Run the gateway and the two services (does this by default) by running node index.js.

4. Query the gateway for directives

5. See that no requires directive will exist

6. Query service 2 for directives

7. See that the @requires directive exists

Here is the query you can run to get directives.

query IntrospectionQuery {
  __schema {
    directives {
      name
      description
      locations
    }
  }
}

[mcollina]

Good spot! Would you like to send a Pull Request to address this issue? Remember to add unit tests.

[aleccool213]

Sure thing!

It isn't quite clear to me in the codebase where the omitting of @requires occurs but I see its being used in relation to the gateway here:

mercurius/lib/util.js

Line 20 in bc83aad

if (directive === 'extends' || directive === 'requires') {

I'll start there and comment back when I see a clear path forward.

[aleccool213]

The reason this happens is that the gateway-specific directives are filtered out of the final list of directives here:

mercurius/lib/federation.js

Line 240 in ea2e50d

const directives = schema.getDirectives()

This is because they aren't used in the final gateway schema, except the requires is used in both locations. I propose we do not filter out the requires directive when building the gateway schema.