@substate/core

@substate/core is the first package in the Substate monorepo. It provides typed reactive store primitives built around substores, selectors, mutations, subscriptions, dependency tracking, and snapshots.

This package is published from the open-source Substate monorepo:

• Repository: https://github.com/dumitru-arsenii/substate
• Package source: https://github.com/dumitru-arsenii/substate/tree/main/packages/core
• npm: https://www.npmjs.com/package/@substate/core
• Issues: https://github.com/dumitru-arsenii/substate/issues

Installation

npm install @substate/core

Quick Start

import { createStore, createSubStore } from "@substate/core";

const counter = createSubStore({}, (builder) => {
  const setCount = builder.mutation(async (args: { value: number }) => ({
    value: args.value,
  }));

  const doubled = builder
    .withDependencies({ setCount })
    .selector(async ({ setCount }) => ({
      value: setCount.value * 2,
    }));

  return { setCount, doubled };
});

const store = createStore({ counter });

await store.counter.setCount().run({ value: 2 });

const result = await store.counter.doubled().resolve();

console.log(result.value); // 4

Core API

createSubStore(dependencies, factory)

Creates a substore definition. The factory receives a builder with methods for:

• selector
• mutation
• subscription
• isolated
• withDependencies

Substores can depend on other substores, and dependent flows can read ready dependency data through the builder.

createStore(substores, snapshot?)

Initializes a store from substore definitions and optional snapshot data.

The returned store includes the initialized substores plus runtime helpers:

• isPending()
• whenIdle()
• getSnapshot()

Results

Flow streams expose discriminated result objects:

type SubstateResult<T> =
  | { ready: false }
  | { ready: true; success: true; data: T }
  | { ready: true; success: false; error: unknown };

Development

From the repository root:

pnpm install
pnpm --filter @substate/core test
pnpm --filter @substate/core typecheck
pnpm --filter @substate/core build