Using dataloader, expecting records to not exist, and not propagating those "errors" to the client

[tbehunin]

I'm using @pothos/plugin-dataloader (with graphql-yoga) to "bulk get by id's". I expect it to return a partial list of records. From what I've read in the docs, in order to use that correctly, I need to:

1. Return them in the same order I received the id's, and
2. When the item isn't found or does not exist, return a new Error() object.

This has been working. However a couple annoyances: my console outputs these errors for each Error object I return in the list, I'm assuming due to when the promise is resolved. In my mind, these aren't errors - just non-existing records. In addition to the "found" records being returned after making a graphql query, an "errors" array is also returned with "sensible defaults as error masking" (as defined here, presumably a graphql-yoga thing):

  "errors": [
    {
      "message": "Unexpected error.",
      "path": [
        "myQuery",
        0,
        "myField"
      ],
      "extensions": {
        "code": "DOWNSTREAM_SERVICE_ERROR"
      }
    },
    ...

Here's a sample of my code:

export const myUnionType = builder.loadableUnion<string, typeof myType1 | typeof myType2>('MyUnionType', {
  types: [myType1, myType2],
  resolveType: (obj) => `${obj.type}`,
  load: async (ids: string[]) => {
    const list = await service.getDataByIds(ids);
    
    // Reorder
    return ids.map((id) => {
      const item = list.find(x => x === id);
      return item ? item : new Error(`Item with id ${id} not found`);
    });
  },
});

Ideally I'd like to not return an Error object - just a null object. That would stop the errors in the console and presumably in the query response. But if I replace the new Error() with null, I get more typescript errors:

Type 'null' is not assignable to type 'MyType1 | MyType2 | Error'.

It's been a "whack-a-mole" trying to resolve one typescript error after another. Any ideas what I'm doing wrong or how I can achieve this?

[hayes]

Here's a working example (extracted from pothos tests)

https://stackblitz.com/edit/typescript-qhw5q5fl?file=tsconfig.json,index.ts

[tbehunin]

Thank you! OMG I just needed to remove the generic block <string, typeof myType1 | typeof myType2> and the typescript errors disappeared. I wasn't sure how to use the loadableUnion since there wasn't any documentation on it, so I was just fumbling around. Thanks again!