Apollo Server Express with stitched schema swallows errors

[GarethSharpe]

Intended outcome

When using a GraphQL gateway to schema stitch GraphQL µservices, the error messages thrown by the µservices should bubble up to the gateway and should be presented unaltered.

Actual outcome

A generic INTERNAL_SERVER_ERROR error code is displayed to the gateway client along with a message containing an `[object Object] which cannot be extracted. The µservice throws the correct error.

µservice error:

{ [GraphQLError: Session expired or invalid]
  message: 'Session expired or invalid',
  locations: [ { line: x, column: x } ],
  path: [ 'xxx' ],
  extensions: 
   { code: 'INTERNAL_SERVER_ERROR',
     exception: 
      { name: 'INVALID_SESSION_ID',
        errorCode: 'INVALID_SESSION_ID',
        stacktrace: [Array] } } }

gateway error:

{ [GraphQLError: [object Object]]
  message: '[object Object]',
  locations: [ { line: x, column: x } ],
  path: [ 'xxx' ],
  extensions: 
   { code: 'INTERNAL_SERVER_ERROR',
     exception: { errors: [Array], stacktrace: [Array] } } }

How to reproduce the issue

Stitch two schemas together. Force one to throw a specific error (AutenticationError, etc). Observe response from the Apollo Server that stitched the schemas.

Potential fix

Move to graphql-tools@next (5.0.0-rc.0). Here is the ongoing discussion.

[martijnwalraven]

Closing this because it will have to be resolved in graphql-tools, but note that schema stitching is being deprecated in favor of federation.