Immer adapter ​

@sometic/store-immer adds draft-style updates on top of @sometic/store without pulling Immer into the default store bundle. immer is a peer dependency.

Overview ​

ExportRole
createImmerStoreDisposable store plus produce(updater)
ImmerUpdater(draft: Draft<TState>) => void
ImmerStoreDisposableStore extended with produce

State must be an object (Immer's produce constraint). You still get get, set, update, batch, subscribe, and dispose from the underlying store.

When to use ​

  • Deep nested trees where immutable spreads become noisy
  • Existing Immer habits in an app that also binds Sometic engines
  • Localized mutable drafts while keeping the public store immutable

When not to use ​

  • Flat counters, flags, or small preference objects (plain update is enough)
  • Avoiding the immer peer weight in hot paths or size-sensitive bundles
  • Expecting Redux Toolkit-style slices or middleware (out of scope)

Installation ​

Install the adapter and the peer:

pnpm
pnpm add @sometic/store-immer immer @sometic/store
npm
npm install @sometic/store-immer immer @sometic/store
yarn
yarn add @sometic/store-immer immer @sometic/store
bun
bun add @sometic/store-immer immer @sometic/store

@sometic/store is also a peer (>=0.0.1). immer must satisfy ^10.0.0.

Usage ​

ts
import { createImmerStore } from "@sometic/store-immer";

type TodosState = {
    items: Array<{ id: string; title: string; done: boolean }>;
};

const store = createImmerStore<TodosState>({
    items: [{ id: "1", title: "Ship docs", done: false }],
});

store.produce((draft) => {
    const first = draft.items[0];
    if (first) {
        first.done = true;
    }
    draft.items.push({ id: "2", title: "Write FAQ", done: false });
});

store.get().items[0]?.done; // true

store.dispose();
js
import { createImmerStore } from "@sometic/store-immer";

const store = createImmerStore({
    items: [{ id: "1", title: "Ship docs", done: false }],
});

store.produce((draft) => {
    const first = draft.items[0];
    if (first) {
        first.done = true;
    }
    draft.items.push({ id: "2", title: "Write FAQ", done: false });
});

store.dispose();

produce is implemented as store.set(produce(store.get(), updater)). Equality, batching, and subscribe behavior match createStore. You can still call set / update when a full replacement is clearer.

ts
store.batch(() => {
    store.produce((draft) => {
        draft.items[0]!.done = true;
    });
    store.produce((draft) => {
        draft.items.push({ id: "3", title: "Batch", done: false });
    });
});

Optional equalityFn is forwarded to createStore:

ts
const store = createImmerStore({ nested: { n: 0 } }, { equalityFn: Object.is });

How it works ​

  1. createImmerStore wraps createStore from @sometic/store.
  2. produce(updater) runs Immer's produce against the current state and sets the result.
  3. Listeners see immutable next states (structural sharing from Immer), same as any other store commit.
  4. No persistence or cross-tab logic lives here; compose with @sometic/store/persistent or /cross-tab at the app layer if needed (wrap or mirror state yourself).

Edge cases ​

CaseBehavior
Non-object initial stateTypeScript rejects; Immer expects objects
Mutating outside produceDo not mutate get() results; treat them as frozen
produce that returns a valuePrefer recipe side effects on draft (Immer rules)
Disposed storeSame throws as core store
Missing immer peerInstall fails / runtime import fails; keep it explicit

Performance notes ​

  • Adapter itself targets ≤ 1 KB gzip; immer is extra and often dominates size.
  • Prefer plain createStore for small slices.
  • Structural sharing helps large trees; for tiny state it is overhead without benefit.

FAQ ​

Why is Immer a peer instead of a dependency? ​

Most Sometic stores never need drafts. Peer-forcing immer would tax every consumer of @sometic/store. The adapter keeps the choice explicit.

Does createImmerStore replace createStore? ​

No. Use it only where drafts help. Adapters (useStore) accept either store shape because both implement get / subscribe.

Can I persist an Immer store? ​

Not as a one-liner from this package. Persist the same state shape with createPersistentStore, or keep an Immer store and write your own hydrate/persist bridge. Theme persistence uses the plain persistent store, not Immer.

Does produce notify selectors? ​

Yes. After set, select and framework useStore selectors re-run against the next immutable state.

Is this Redux Toolkit? ​

No. No slices, middleware, or entity adapters. Only draft updates on the Sometic store contract.

TypeScript: why TState extends object? ​

That matches Immer's produce typing for draftable values.

Can I use select with an Immer store? ​

Yes. Import select from @sometic/store and pass the immer store.

What about SSR? ​

Same as core store: no import-time browser access. Immer runs wherever your bundle runs.

Comparison ​

ApproachTradeoff
Plain update spreadsZero Immer cost; verbose for deep trees
@sometic/store-immerDraft DX; peer weight; object-only state
App-level Zustand + ImmerFine at the app boundary; do not pull into Sometic cores