@systemfsoftware/oxlint-plugin

Catch Effect-TS violations before they hit review: ban classes, string errors, bare promises, native timers, and every other pattern the System F Software Constitution forbids.

Effect enforces a discipline — no Date.now(), no Set or Map inside an Effect, no barrel exports, no string errors. But the compiler doesn't catch these. And code review catches them too late, one PR at a time, after someone already wrote the wrong thing.

This plugin turns those rules into instant feedback. Wire it into your oxlint.config.ts, and every pnpm lint run checks every file before commit. Eighteen rules cover the constitution's pure-core and boundary articles — from ban-classes and ban-error-string to no-io-boundary-tests and no-logging-in-catch.

Quick start

pnpm add -D @systemfsoftware/oxlint-plugin

Configure it in your oxlint config:

import { defineConfig } from 'oxlint'

export default defineConfig({
  jsPlugins: ['@systemfsoftware/oxlint-plugin'],
  rules: {
    '@systemfsoftware/oxlint-plugin/ban-classes': 'error',
  },
})

Then lint:

pnpm oxlint

A class that does not extend one of the sanctioned Effect v4 constructor expressions (Context.Service, Schema.Class, Data.TaggedClass, the Rpc factories, ...) is reported and rejected. No legacy class — and no bare class — survives to review.

A service declaration carries the effect that builds it:

class Store extends Context.Service<Store, StoreShape>()('app/Store', {
  make: Effect.gen(function*() {/* … */}),
}) {
  static readonly layer = Layer.effect(this, this.make)
}

Effect.Service is reported wherever it appears — the Effect module exports no Service in v4, and Context exports Key, Service and Reference but no Tag.

Whether a service should carry make is not linted, and deliberately so. A Context.Service with no make is a port, and a port's own file routinely holds exactly one layer — a stub or a noop — while the real implementations live elsewhere. No rule reading one file can separate that stub from a canonical construction, so a check that fired on "one layer beside a service" would tell a port to promote its stub. Put the construction on the class when the module owns it; that call is a review matter.

For a full setup with every rule enabled at the recommended severity, extend the shared base config:

import baseConfig from '@systemfsoftware/oxlint-config'

export default defineConfig({ ...baseConfig })

Browse src/rules/ for every rule and its implementation — that list is always current.

Tech stack

| Component | Technology | Version | | ---------- | --------------- | ------- | | Runtime | Node.js | 24.x | | Linter | oxlint | 1.60.x | | Plugin API | @oxlint/plugins | 1.60.x | | Language | TypeScript | 6.0.x |

License

Apache 2.0