tagged-error

Generate Effect TaggedError types for error handling. Use when adding new error types or improving error handling.

Stars 163

Forks 31

Install this agent skill to your Project

npx add-skill https://github.com/majiayu000/claude-skill-registry/tree/main/skills/data/tagged-error

SKILL.md

Tagged Error Generator

Generate Effect Data.TaggedError types following project conventions.

Error Location

packages/wowlab-core/src/internal/errors/Errors.ts

Basic Error Template

import * as Data from "effect/Data";

export class MyError extends Data.TaggedError("MyError")<{
  readonly message: string;
  readonly cause?: unknown;
}> {}

Error with Context

import * as Branded from "../schemas/Branded.js";
import * as Entities from "../entities/index.js";

export class SpellNotFound extends Data.TaggedError("SpellNotFound")<{
  readonly unitId: Branded.UnitID;
  readonly spellId: number;
}> {}

export class CastFailed extends Data.TaggedError("CastFailed")<{
  readonly reason: string;
  readonly spell: Entities.Spell.Spell;
  readonly caster?: Entities.Unit.Unit;
}> {}

Error Union Types

Group related errors:

export type RotationError =
  | NoChargesAvailable
  | SpellNotFound
  | SpellOnCooldown
  | UnitNotFound;

export type CombatLogError = QueueEmpty | HandlerError | EventValidationError;

Naming Conventions

Error class: {Thing}{Problem} - e.g., SpellNotFound, CastFailed
Tag: Same as class name
Include relevant context in payload (IDs, entities, messages)

Usage in Effects

import * as Errors from "@wowlab/core/Errors";

// Failing with error
yield *
  Effect.fail(
    new Errors.SpellNotFound({
      unitId,
      spellId,
    }),
  );

// In function signature
const cast = (
  spellId: number,
): Effect.Effect<CastResult, Errors.SpellNotFound | Errors.SpellOnCooldown> =>
  Effect.gen(function* () {
    // ...
  });

Instructions

Identify what can fail
Design payload with useful context
Create error class with TaggedError
Add to union type if applicable
Update function signatures to include error