effect-io-ai

Package: effect
Module: Effect

Effect.catchReason

Catches a specific reason within a tagged error.

When to use

Use to handle one nested reason inside an Effect’s tagged error while preserving the parent error shape for unmatched reasons.

Details

Use this to handle nested error causes without removing the parent error from the error channel. The handler receives the unwrapped reason.

Example (Handling an error reason)

import { Data, Effect } from "effect"

class RateLimitError extends Data.TaggedError("RateLimitError")<{
  retryAfter: number
}> {}

class QuotaExceededError extends Data.TaggedError("QuotaExceededError")<{
  limit: number
}> {}

class AiError extends Data.TaggedError("AiError")<{
  reason: RateLimitError | QuotaExceededError
}> {}

declare const program: Effect.Effect<string, AiError>

// Handle rate limits specifically
const handled = program.pipe(
  Effect.catchReason("AiError", "RateLimitError", (reason) =>
    Effect.succeed(`Retry after ${reason.retryAfter}s`)
  )
)

See

• catchReasons for handling several nested reason tags

Signature

declare const catchReason: { <K extends Tags<E>, E, RK extends ReasonTags<ExtractTag<NoInfer<E>, K>>, A2, E2, R2, A3 = unassigned, E3 = never, R3 = never>(errorTag: K, reasonTag: RK, f: (reason: ExtractReason<ExtractTag<NoInfer<E>, K>, RK>, error: NarrowReason<ExtractTag<NoInfer<E>, K>, RK>) => Effect<A2, E2, R2>, orElse?: ((reasons: ExcludeReason<ExtractTag<NoInfer<E>, K>, RK>, error: OmitReason<ExtractTag<NoInfer<E>, K>, RK>) => Effect<A3, E3, R3>) | undefined): <A, R>(self: Effect<A, E, R>) => Effect<A | A2 | Exclude<A3, unassigned>, ExcludeTag<E, K> | E2 | E3 | (A3 extends unassigned ? ExtractTag<E, K> : never), R | R2 | R3>; <A, E, R, K extends Tags<E>, RK extends ReasonTags<ExtractTag<E, K>>, A2, E2, R2, A3 = unassigned, E3 = never, R3 = never>(self: Effect<A, E, R>, errorTag: K, reasonTag: RK, f: (reason: ExtractReason<ExtractTag<E, K>, RK>, error: NarrowReason<ExtractTag<E, K>, RK>) => Effect<A2, E2, R2>, orElse?: ((reasons: ExcludeReason<ExtractTag<E, K>, RK>, error: OmitReason<ExtractTag<E, K>, RK>) => Effect<A3, E3, R3>) | undefined): Effect<A | A2 | Exclude<A3, unassigned>, ExcludeTag<E, K> | E2 | E3 | (A3 extends unassigned ? ExtractTag<E, K> : never), R | R2 | R3>; }

Source

Since v4.0.0