Introduction

@fuiste/dependencies is a small TypeScript library for wiring programs with typed service tags, immutable contexts, and composable dependency recipes.

It is inspired by Effect’s Layer, but it keeps the local surface area narrow:

Context

An immutable map of services addressed by typed tags.

Dependency

A recipe that builds one or more services from declared requirements.

Scope

A finalizer stack for resources that need deterministic release.

Result

A tiny success-or-failure value for build and use outcomes.

The point is not to make TypeScript pretend it has a runtime module system. The point is to make application construction explicit, typed, replaceable, and hostile to spooky mutable globals.

import { Context, Dependency, Result, compose, use } from '@fuiste/dependencies'

const Config = Context.Tag<{ appName: string }>('docs/config')
const Greeter = Context.Tag<{ greet: () => string }>('docs/greeter')

const config = Dependency.succeed(Config, { appName: 'Dependencies' })
const greeter = Dependency.sync(Greeter, [Config], (context) => ({
  greet: () => `hello from ${Context.get(context, Config).appName}`,
}))

const result = await use(compose(config, greeter), (context) => {
  return Context.get(context, Greeter).greet()
})

if (Result.isOk(result)) {
  console.log(result.value)
}

What This Library Optimizes For

Service wiring that is explicit at the value level.
Type inference for provided and required services.
Test substitution without mutating global containers.
Scoped resources that release in last-in-first-out order.
Small primitives that compose without a framework-shaped invoice.

Install

pnpm add @fuiste/dependencies

Use npm, yarn, or bun if that is your chosen package manager weather.