Errors

{
  "error": {
    "code": "MODULE_NOT_FOUND",
    "message": "…",
    "diagnostics": [{ "code": "…", "message": "…" }]
  }
}

// Every failure is the same JSON envelope on every service. Branch on `code`,
// never on the message.
const origin = process.env.CDN_ORIGIN ?? process.env.DEV_ORIGIN;

// The options of the contract default to published delivery, so a development service refuses them with
// OPTION_UNSUPPORTED before it looks at the identity. A development consumer always asks for its output.
const development = !process.env.CDN_ORIGIN;
const options = development ? 'target=node&format=esm&env=development&min=false&sourcemap=inline' : 'target=browser&format=esm';

// A well-formed identity that no service holds
const request = `/m/@example/does-not-exist@0.0.1/modules/main?${options}`;

const response = await fetch(new URL(request, origin));
const type = response.headers.get('content-type') ?? '';

if (response.ok || !type.includes('application/json')) {
	console.log(`unexpected answer: ${response.status} ${type}`);
	process.exit(1);
}

const { error } = await response.json();
console.log(`${response.status} ${error.code}`);
console.log(error.message);
for (const diagnostic of error.diagnostics ?? []) console.log(`  ${diagnostic.code}: ${diagnostic.message}`);

if (error.code !== 'PACKAGE_NOT_FOUND') process.exitCode = 1;

// A published service only retrieves. A valid request for an output that was
// not prepared is a 404 with OUTPUT_NOT_AVAILABLE, and asking again changes
// nothing: no GET starts a build.
const origin = process.env.CDN_ORIGIN;

// Set UNPREPARED_REQUEST to a valid option set that your release did not prepare
const request = process.env.UNPREPARED_REQUEST ?? '/m/@example/shared@1.0.0/modules/text?target=node&format=cjs';

for (const attempt of [1, 2]) {
	const response = await fetch(new URL(request, origin));
	const { error } = await response.json();
	console.log(`attempt ${attempt}: ${response.status} ${error.code}`);
	console.log(`  Cache-Control: ${response.headers.get('cache-control')}`);

	const acceptable = ['OUTPUT_NOT_AVAILABLE', 'OPTION_UNSUPPORTED'].includes(error.code);
	if (!acceptable) process.exitCode = 1;
}

import { ContractError } from '@beyond-js/artifact-api';

const response = await fetch(url);
if (!response.ok) {
	const error = ContractError.from(response.status, await response.json());
	error.code; // 'OUTPUT_NOT_AVAILABLE'
	error.status; // 404
	error.diagnostics; // compiler diagnostics of a failed build, when present
}