API reference

Types

import type { Either, EitherAsync } from "@ngwes/mini-fp";

/** What a step or a hook may return: an Either, or anything that resolves to one. */
type StepResult<E, Ctx> = Either<E, Ctx> | PromiseLike<Either<E, Ctx>>;

type Step<E, Ctx> = (ctx: Readonly<Ctx>) => StepResult<E, Ctx>;

interface PipelineOptions<E, Ctx extends object> {
  /** A step returned left(error). Optional: by default the error stops the pipeline. */
  onLeft?: (error: E, ctx: Readonly<Ctx>) => StepResult<E, Ctx>;
  /** A step threw or its promise rejected. */
  onException: (exception: unknown, ctx: Readonly<Ctx>) => StepResult<E, Ctx>;
  /** A step changed or removed a value an earlier step had written. */
  onConflictingKeys: (
    keys: ReadonlyArray<keyof Ctx & string>,
    ctx: Readonly<Ctx>,  // the context the step received
    next: Readonly<Ctx>, // the context the step returned
  ) => StepResult<E, Ctx>;
}

type DynamicStepModule<E, Ctx> =
  | { default: Step<E, Ctx> }
  | { default: ReadonlyArray<Step<E, Ctx>> }
  | { steps: ReadonlyArray<Step<E, Ctx>> };

type LoadError =
  | { tag: "not-found"; path: string; cause: unknown }
  | { tag: "import-failed"; path: string; cause: unknown }
  | { tag: "invalid-export"; path: string; detail: string };

Functions

Function	Returns
Pipeline(ctx, steps, options)	EitherAsync<E, Readonly<Ctx>>
loadSteps<E, Ctx>(paths)	EitherAsync<ReadonlyArray<LoadError>, ReadonlyArray<Step<E, Ctx>>>
loadStepsFromDir<E, Ctx>(dir, options?)	EitherAsync<ReadonlyArray<LoadError>, ReadonlyArray<Step<E, Ctx>>>

The package exports Pipeline, loadSteps and loadStepsFromDir, and the types Step, StepResult, PipelineOptions, DynamicStepModule and LoadError.