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oxlint-plugin-effect

single-style-per-function

Intent: a function is entirely Effect or not Effect at all.

// ❌ no
export const POST = async (request: Request) => {
    const form = await request.formData()
    const created = await Effect.runPromise(Effect.result(createEvent(form)))
    // …
}


// ✅ yes: promises lifted with Effect.tryPromise
const createEvent = Effect.fn("events.create")(function* (request: Request) {
    const form = yield* Effect.tryPromise({
        try: () => request.formData(),
        catch: () => new BadRequest({ message: "invalid form data" }),
    })
    // …
})

Trigger: async, await and .then( in a function that builds Effects: an Effect generator, or a function using an Effect.* member. A test/it callback (.only, .each(…) and the like included) or a beforeAll/afterAll/beforeEach/afterEach hook, and in test files any other function except an Effect generator, is reported once, on the function, when more than one of its awaits, or any .then(, involves Effect: has an Effect.* member in its expression, nested callbacks and Effect.run* included.

Exemptions and blind spots: Effect.run* alone does not make a function effectful: it is how an async boundary hands over to Effect, and where it may appear is decided by run-only-in-runner. An async function that renders JSX itself, not only in nested callbacks, is a Server Component: how it turns failures into UI is left to the application. A test, hook or test helper may await promise-based fixtures (a container, an identity provider), then one Effect program, and assert on its result. A step that reaches Effect only through a helper (await run(seed)) is not counted.

Why: errors travel on two channels, exceptions and Effect, and neither sees them all.

Options:

Fix: none