One Error Shape

Part of the REST APIs section of Coddy's Node.js journey. Lesson 8 of 18.

Your API answers errors in two shapes now: a string for a 404 and zod's object for a 400. A client has to handle each one. Pick one shape for every error:

{ "error": { "code": "not_found", "message": "Invoice not found" } }

{ "error": { "code": "invalid_body", "message": "Too small: ...",
             "fields": { "amount": ["Too small: expected number to be >0"] } } }

code is for programs: it never changes, so a client can compare it. message is for people, and its wording may change. fields tells a form which input to mark. Write the shape in one function and call it from every route, so no route can drift:

sendError(res, 404, 'not_found', 'Invoice not found');

Challenge

Easy

Write sendError in errors.js: { "error": { "code", "message" } } with the status, plus fields only when given.
Use it for every 404 (code not_found), sendInvalid for every bad body, and sendError in server.js's error handler (invalid_json, server_error).

Send DELETE /api/tasks/99, then POST with { "title": 123 }.

Try it yourself

import { z } from 'zod';

// Sends every error in one shape:
// { "error": { "code": "not_found", "message": "Task not found" } }
// with "fields" added only when it is given.
export const sendError = (res, status, code, message, fields) => {
    // Send the answer here
};

// A zod error as a 400: its first problem as the message, each field's
// problems in fields.
export const sendInvalid = (res, zodError) =>
    sendError(res, 400, 'invalid_body', zodError.issues[0].message, z.flattenError(zodError).fieldErrors);