How to capture the GraphQL error message in Relay?

Question

On my server, my implementation of GraphQL is using Flask, Graphene, and SQLAlchemy. Ideally I would like to be able to simply manipulate the headers and return a 401 error response, but GraphQL returns everything as 200.

Using flask.abort(401) however I am at least able to obtain this response:

...
"errors": [
  {
    "message": "401 Unauthorized: The server could not verify that you are authorized to access the URL requested.  You either supplied the wrong credentials (e.g. a bad password), or your browser doesn't understand how to supply the credentials required.",
    "locations": [
      {
      "line": 11,
      "column": 3
      }
    ]
  }
]
...

I see this as a compromise that I can work with at this point in time. However; because nothing can just be that simple... I am not sure as to how I can grab this error message. I've read that there might an issue with the QueryRenderer itself that swallows these GraphQL errors but I can manage to intercept them in the Network object in the Environment... that essentially looks something like this.

Promise {[[PromiseStatus]]: "resolved", [[PromiseValue]]: {…}}
  __proto__: Promise[
    [PromiseStatus]]: "resolved"
    [[PromiseValue]]: Object
      data: {viewer: {…}}
      errors: Array(4)
        0: {locations: Array(1), message: "401 Unauthorized: The server could not verify that…nderstand how to supply the credentials required."}
        1: {locations: Array(1), message: "401 Unauthorized: The server could not verify that…nderstand how to supply the credentials required."}
        2: {locations: Array(1), message: "401 Unauthorized: The server could not verify that…nderstand how to supply the credentials required."}
        3: {locations: Array(1), message: "401 Unauthorized: The server could not verify that…nderstand how to supply the credentials required."}
      length: 4
      __proto__: Array(0)
    __proto__:Object

I don't really feel like handling this error at the Network layer of my Environment would be the proper way to manage this. The QueryRenderer seems to make the most sense... I have set it up essentially as the single source of truth.

I am using Relay Modern by the way if that wasn't obvious. So more likely than not any solutions based around Relay Classic will not apply.

Edit: Error message aside, my motivation for this was proper handling of JWT tokens. I think the solution I am looking for isn't related to handling these error responses but rather expanding my understanding of JWT.

I didn't realize that my client would easily be able to decode the JWT using a package such as the jwt-decode which then gives me access to expiration information... which ultimately I foresee leading me to some form of middleware implementation that would assess the amount of time remaining on the JWT and if a refresh is necessary.

Answer 1

You can handle server errros in the onCompleted callback: https://github.com/facebook/relay/pull/1938/files