Tagged Error Generator

Name: tagged-error
Rating: 78
Author: legacy3

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