Could you make error messages more informative?

[antonvialibri1]

Hello,

Thank you for this project! I have one request about error messages.

When an error occurs, for example when a custom merge fails because it uses mergeObjects and either one of incoming or existing isn't an array (because perhaps there's a bug on the developer's end), this is the error we get:

Cannot automatically merge arrays

import { ApolloClient, InMemoryCache } from '@apollo/client';

const simpleMerge = {
  merge(existing, incoming, { mergeObjects }) {
    return mergeObjects(existing, incoming); // This may fail if either `existing` or `incoming` isn't an array.
  }
};

const cacheOptions = {
  typePolicies: {
    SomeType: {
      fields: {
        someTypeItems: simpleMerge,
      }
    },
};

const cache = new InMemoryCache(cacheOptions);

It would be useful to at least have the name of the field involved, e.g.:

Cannot automatically merge arrays for `someTypeItems` field. Either one of `existing` or `incoming` is not an array. Check your merge function or the field's value.

Something like this would save a lot of hassle and time spent in debugging trying to understand what's going on.

[jerelmiller]

Hey @antonvialibri1 👋

Thanks for the suggestion! This seems like a reasonable request! Feel free to submit a PR if you're interested in getting this in soon!