Improving typing custom key extractors for urql-graphcache-exchange

[jedahan]

I have a field artistId: string which acts as the id for one of my graphql types.

The cacheExchange KeyingConfig type doesn't know what fields I have, so we need to tell typescript. Maybe we can make it a Record<any, string> or make a generic KeyExtractField<T: SomeTypeScriptType> to allow passing in a known compile-time type?

Fails with "string | null" -> number type error:

cacheExchange({
  keys: {
    Artist: (artist) => artist.artistId,
  },
})

Works fine

cacheExchange({
  keys: {
    Artist: (artist: Data & { artistId: string }) =>
      artist.artistId,
    },
  }
})

[JoviDeCroock]

I think something like this should be able to help #901 (comment)

[jedahan]

Excellent, will explore shortly