fix: enforce limit of 2 auction triggers at compile time

[anonvt]

The SDK allows an auction to have 3 triggers, but the API allows at most two.

Adde compile time validation to ensure correct formation.

[jbergstroem]

Left feedback. Also.. tests.

[anonvt]

@jbergstroem changed to compile time validation, we'll need to version bump though.
Also, not 100% sure on how to make a meaningful compile time test

[jbergstroem]

how do we then test invalid combinations?

[anonvt]

// @ts-expect-error can be an exit
I've changed the interface to accept the wrong combination and it fails (it expects an error, there's no error, so the annotation fails the "test")

[anonvt]

@jbergstroem

[jbergstroem]

Wouldn't this allow any error, not just the error we're looking for? Are we sure this is the right path?

[anonvt]

added which specific error we're looking for 👍

[jbergstroem]

Can we simplify your types? The permutations looks complicated. How about something like:

type CategoryType =
  | AuctionSingleCategory
  | AuctionMultipleCategories
  | AuctionDisjunctiveCategories;

type AuctionConstraints =
  | { category: CategoryType; products: AuctionProduct; searchQuery?: never }
  | { category: CategoryType; products?: never; searchQuery: string }
  | { category?: never; products: AuctionProduct; searchQuery: string }
  | { category: CategoryType; products?: never; searchQuery?: never }
  | { category?: never; products: AuctionProduct; searchQuery?: never }
  | { category?: never; products?: never; searchQuery: string }
  | { category?: never; products?: never; searchQuery?: never };

type AuctionBase = AuctionBaseFields & AuctionConstraints;

interface SponsoredListingAuction extends Omit<AuctionBase, "type"> {
  type: "listings";
}

interface BannerAuction extends Omit<AuctionBase, "type"> {
  device?: DeviceType;
  slotId: string;
  type: "banners";
}

export interface Auction {
  auctions: (SponsoredListingAuction | BannerAuction)[];
}