gust-stdlib 0.2.0

Standard library of reusable Gust state machines (circuit breaker, retry, saga, rate limiter, and more)
Documentation 
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// EngineFailure: typed runtime/engine failure for workflow-style machines.
//
// Corsac and other workflow runtimes use Gust as the contract language for
// compiled workflows. They need a stable, typed failure surface so that
// retry policies, replay semantics, and observability can reason about
// failures without parsing strings.
//
// This file ships as `gust_stdlib::ENGINE_FAILURE`. Import it in a .gu
// project with:
//
//     use std::EngineFailure;
//
// and use the variants in state field types, e.g.:
//
//     state Failed(failure: EngineFailure)
//
// Domain-specific failure enums can wrap this to preserve the engine
// layer while adding domain variants:
//
//     enum SlackFailure {
//         Engine(EngineFailure),
//         RateLimited(i64),
//         ChannelNotFound(String),
//     }
//
// Variant payload positions (documented here because Gust enum variants
// currently take positional types, not named fields):
//
//   UserError(reason)
//       reason: String
//
//   SystemError(reason, attempt)
//       reason:  String  -- human-readable description
//       attempt: i64     -- attempt number (1-based)
//
//   IntegrationError(service, status_code, body)
//       service:     String  -- downstream service identifier
//       status_code: i64     -- HTTP-style status from the service
//       body:        String  -- raw response body
//
//   Timeout(wall_clock_ms)
//       wall_clock_ms: i64   -- elapsed milliseconds at the timeout
//
//   Cancelled(requested_by)
//       requested_by: String -- opaque canceller identifier

enum EngineFailure {
    UserError(String),
    SystemError(String, i64),
    IntegrationError(String, i64, String),
    Timeout(i64),
    Cancelled(String),
}