[FTWinston]

A snapshot of a MapSchema<T> (or of a IMap<string, T>) is typed as Record<string, T> which is awkward for testing it e.g. in storybook. If it instead is typed Partial<Record<string, T>>.

A Record asserts that every key is present, whereas a Map does nothing of the sort, so I think making the frontend type Partial is the more accurate approach.

[endel]

Thanks @FTWinston! Merged and released in 0.18.3.

I adjusted the approach before merging:

• Union keys become optional, for both IMap<K, V> and MapSchema<V, K>. MapSchema is matched by an earlier branch of Snapshot, so the original change never reached it (that branch also dropped K). Snapshot of IMap<CardTrait, ExtraTraitType> is now { readonly [P in CardTrait]?: ExtraTraitType }.
• String keys keep their index signature. Partial<Record<string, T>> resolves to { [k: string]: T | undefined }, which turns every Object.values(snap.players).map(p => p.name) into a 'p' is possibly 'undefined' error, though entries are never undefined at runtime. To get checked lookups on string-keyed maps, noUncheckedIndexedAccess types snap[id] as T | undefined and keeps iteration exact.

I checked this against AllHands: on 0.18.3 the as Record<CardTrait, ExtraTraitType> cast in WeaponSlot.stories.tsx can go (along with the then-unused CardTrait import), and the rest of the project type-checks unchanged.

[FTWinston]

Nice one, thank you!