Intercept and customise Apollo GraphQL Errors

Question

I am using simple error handling mechanism based on ApolloError (or derived one) to throw errors from my GraphQL server. For example:

throw new AuthenticationError("Token not present in the request");

In this case, client would receive something like:

{
  "errors": [
    {
      "message": "Token not present in the request",
      ...

I would like to somehow intercept those errors before returning the response to the client, in order to translate them to user's language of choice.

How can I do it?

Answer 1

Looking here you can provide the formatError method to your ApolloServer constructor.

const server = new ApolloServer({
  typeDefs,
  resolvers,
  formatError: (err) => {
    if (err.message.includes("xyz")) {
      return new Error('Internal server error');
    }

    return err;
  },
});

Use err.originalError to do type checking

formatError: (err) => {
    if (err.originalError instanceof AuthenticationError) {
      return new Error('Internal server error');
    }

    return err;
  },