jackwener/OpenCLI · error · CommandExecutionError

Chess.com callback returned an invalid response object for $

Error message

Chess.com callback returned an invalid response object for ${url}

What it means

This library fetches a single Chess.com game via the internal callback endpoint /callback/{kind}/game/{id}. After the fetch resolves, it expects a valid Response-like object; if fetch resolved with null, undefined, or a non-object, the command throws CommandExecutionError. This is a defensive invariant check against a misbehaving fetch implementation or a mocked/patched global fetch.

Source

Thrown at clis/chess/game.js:96

        { name: 'game-url', type: 'string', required: true, positional: true, help: 'Full game URL, e.g. https://www.chess.com/game/live/168842570216' },
    ],
    columns: [
        'kind', 'game_id', 'date',
        'white', 'white_rating', 'black', 'black_rating',
        'result', 'winner_color', 'termination',
        'eco', 'time_control', 'rated', 'ply_count', 'url',
    ],
    func: async (kwargs) => {
        const { kind, id } = parseGameUrl(kwargs['game-url']);
        const url = `${CALLBACK_BASE}/${kind}/game/${id}`;
        let resp;
        try {
            resp = await fetch(url, { headers: { 'User-Agent': UA, accept: 'application/json' } });
        } catch (error) {
            throw new CommandExecutionError(`Failed to fetch Chess.com callback ${url}: ${error?.message || error}`);
        }
        if (!resp || typeof resp !== 'object') {
            throw new CommandExecutionError(`Chess.com callback returned an invalid response object for ${url}`);
        }
        if (resp.status === 404) {
            throw new EmptyResultError(`Chess.com has no ${kind} game with id ${id}`);
        }
        if (!resp.ok) {
            throw new CommandExecutionError(`Chess.com callback returned HTTP ${resp.status} for ${url}`);
        }
        let payload;
        try {
            payload = await resp.json();
        } catch (error) {
            throw new CommandExecutionError(`Chess.com callback returned malformed JSON for ${url}: ${error?.message || error}`);
        }
        return [summarizeGame({ kind, id, payload })];
    },
});

export const __test__ = { parseGameUrl, summarizeGame };

View on GitHub (pinned to 49907e53dc)

Solutions

Check that any global fetch mock/polyfill returns a Response-like object (at minimum {status, ok, json()}) for every matched URL
Fix unmatched-route behavior in HTTP mocking libraries (e.g. nock/msw) so unmatched requests return a Response instead of undefined
Run in a runtime with spec-compliant fetch (Node 18+ or undici) instead of a custom polyfill

Example fix

// before (broken mock)
global.fetch = async () => undefined;
// after
const resp = new Response(JSON.stringify({ game: { pgnHeaders: { White: 'a', Black: 'b', Result: '1-0' } } }), { status: 200, headers: { 'content-type': 'application/json' } });
global.fetch = async () => resp;

Defensive patterns

Strategy: type-guard

Validate before calling

// before calling the command, ensure your fetch environment is spec-compliant
if (typeof globalThis.fetch !== 'function') throw new Error('fetch unavailable');

Type guard

function isResponseLike(r) { return !!r && typeof r === 'object' && typeof r.status === 'number' && typeof r.ok === 'boolean' && typeof r.json === 'function'; }

Try / catch

try {
  const rows = await chessGameCmd(url);
} catch (e) {
  if (/invalid response object/.test(e.message)) {
    // fix or replace the fetch polyfill/mock, then retry
  } else throw e;
}

Prevention

Never stub fetch with functions returning undefined/null; always return a Response object
Test against real fetch (Node 18+) in CI
Pin mocking libs (nock/msw) and configure a fallback for unmatched routes

When it happens

Trigger: fetch() at clis/chess/game.js:91 resolves to a falsy value or a non-object (e.g. a test stub returning undefined, a proxy/patched fetch returning null, or a non-standard runtime whose fetch resolves non-Response values).

Common situations: Running under a test harness with an incomplete fetch mock; custom Node environments with a polyfilled fetch that violates the spec; code interception (e.g. an HTTP mocking lib misconfigured to return undefined for unmatched routes).

Related errors

AI-assisted analysis of jackwener/OpenCLI@49907e53dc (2026-08-29). Data as JSON: /api/errors/06593a4d75670e28. Report an issue: GitHub.