originalError in federation

[ramiel]

When an error occurs in federation, even if it is a GraphqlError, the federation removes the "originalError" message when not in development. Is this expected? As an example, this is in dev

{
  "errors": [
    {
      "message": "Unexpected error.",
      "extensions": {
        "serviceName": "events",
        "code": "DOWNSTREAM_SERVICE_ERROR",
        "originalError": {
          "message": "User identified by email \"[email protected]\" not found"
        }
      }
    }
  ],
  "data": null
}

while this is in production

{
  "errors": [
    {
      "message": "Unexpected error.",
      "extensions": {
        "code": 404,
        "serviceName": "events"
      }
    }
  ],
  "data": null
}

[n1ru4l]

Hey, @ramiel what you are experiencing is error masking which is a security measure to avoid leaking sensitive information. You can learn more here: https://the-guild.dev/graphql/yoga-server/docs/features/error-masking#customize-error-masking and https://the-guild.dev/graphql/yoga-server/docs/features/apollo-federation#handling-subgraph-errors for subgraph error handling.

[ramiel]

This is exactly what I'm talking about. I'm using GraphqlError to let the message pass to the client. This is in fact working correctly in the service itself, but is masked when going through the gateway

[n1ru4l]

Okay, I can see what is happening here.

The error is raised in the subgraph, however, the gateway does not know that this is GraphQLError as it serialized and then again de-serialized to JSON.

I created a reproduction and potential solution that I am discussing with @ardatan over here: #2364

[n1ru4l]

@ramiel We updated the documentation with examples of how to customize error masking for such use cases.

[ramiel]

Great! I see there's a new function called maskError, has this been released already?

[n1ru4l]

Yes try 3.5.1 😇

[ramiel]

So, it's not really working for me, I receive this

{
  "errors": [
    {
      "message": "Unexpected error.",
      "path": [
        "userGetManagedByEmail"
      ],
      "extensions": {
        "code": 404,
        "serviceName": "events"
      }
    }
  ],
  "data": null
}

and, as you can see, it's not working because the code is not DOWNSTREAM_SERVICE_ERROR . Anyway, I got the logic and now I know I can completely disable error masking in the gateway as long as I know the error are masked in the subgraph.
Thank you