Unable to set custom headers on errors

[ustun]

The headers for errors seem to be fixed, one cannot set any headers for errors via any other means (extensions etc).

See

apollo-server/packages/apollo-server-core/src/runHttpQuery.ts

Line 79 in f51aa07

const defaultHeaders = { 'Content-Type': 'application/json' };

The use case is explained in this issue: #3061

Note that I was able to send response headers for successful responses there, but not for errors.

[abernix]

Please try this with the new implementation provided in #2719 and let us know if it's not possible.

Roughly, I think you'd want this:

import { ApolloServer } from 'apollo-server';
const server = new ApolloServer({
  typeDefs,
  resolvers,
  plugins: [
    {
      requestDidStart() {
        return {
          didEncounterErrors({ response, errors }) {
            // You can inspect `errors`, if you'd like!
            response.http.headers.set('Your-Own-Header', 'SEVERITY!');
          }
        }
      },
    },
  ],
});

[ustun]

Hmm, it seems that there are different categories of errors.

I was already catching errors in resolvers and the new plugin also worked for errors in resolvers, however unfortunately that didn't do the trick for parsing or validation errors, e.g. when we send a malformed query from the client.

When a validation error is detected (you ask for a field that is not in typedef), didEncounterErrors function is executed, however that response with headers is ignored, at least for the apollo-server-express.

[PrimarchAlpharius]

@abernix The proposed solution does not work.

In my case, the error (PersistedQueryNotFound) is picked up by didEncounterErrors, but setting of the header is apparently ignored.

At the moment, it appears impossible to customize the headers of (at least some) error responses.
Example, a persisted GET request that yields a PersistedQueryNotFoundError will go through didEncounterError (where setting the header simply does not work and the documentation for this event is next to non-existent) and formatError, where the context is not available.

Is there a way to accomplish this that I am not aware of? If not, would you consider adding support for this? Either allowing it in didEncounterError, or maybe adding a new event willSendErrorResponse (similar to willSendResponse)?

[msdinit]

For anyone trying to resolve this, the problem seems to be that for some errors (namely APQ errors), apollo server forces some pre-defined headers. A temporary workaround is to manually throw an HttpQueryError with your own headers:

didEncounterErrors ({ errors, debug }) {
    if (hasPersistedQueryError(errors)) {
        throw new HttpQueryError(
            200,
            JSON.stringify({ errors: formatApolloErrors(errors, { debug: debug }) }),
            true,
            { 'Cache-Control': 'max-age=0, stale-while-revalidate' }
        )
    }
}