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oxlint-plugin-effect

split-success-path-from-error-handling

Intent: the generator holds only the happy path; error handling lives in the second argument of Effect.fn.

// ❌ no
function* () {
    const x = yield* fetchThing.pipe(Effect.catchTag("NotFound", () => Effect.succeed(fallback)))
}


// ✅ yes: naming the error or giving an alternative is not handling
function* () {
    const x = yield* fetchThing.pipe(Effect.orElseSucceed(() => fallback))
    const y = yield* decode(raw).pipe(Effect.mapError((error) => new BadRequest({ message: error.message })))
}


// ✅ yes: translation in the second argument, which also receives the original arguments
const createEvent = Effect.fn("events.create")(
    function* (request: Request) { /* success only */ },
    (effect, request) => effect.pipe(Effect.catchTags({ BadRequest: (e) => refused(400, e.message) })),
)

Trigger: inside a generator passed to Effect.gen/Effect.fn, callbacks passed to Effect.* combinators included, calls to Effect.catch* (catch, catchAll, catchTag, catchTags, catchIf, catchCause, catchDefect, catchReason, …), either, result, exit, match* and sandbox.

Exemptions and blind spots: pipeables of a nested Effect.fn. Handlers inside the callback of an iteration (forEach, filter, reduce, partition, validate, findFirst, …): they handle each element on its own, and in the pipeables the first failure would stop the rest. Functions the generator only defines, such as an HttpApiBuilder handler or a service method: they are programs of their own. Test files, where the failure is the outcome under observation (yield* Effect.result(op) then expect). A catch, catchTag, catchTags, catchIf or catchFilter whose handlers only die (Effect.die passed directly or as the sole return): it is a selective orDie, declaring the case untracked rather than handling it; a die behind a wrapper or a condition is still reported. A .pipe(Effect.catch…) appended to an Effect.gen escapes; prefer-effect-fn closes that gap.

Why: translation becomes a single exhaustive point instead of catches scattered along the flow.

Options:

Fix: none