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fix(checkout-api): resolve checkout-race-condition #21

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fix(checkout-api): resolve checkout-race-condition #21

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14 changes: 13 additions & 1 deletion demo_app/src/checkout/submit-order.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -14,5 +14,17 @@ export const runCheckoutRaceScenario = async (mode: "concurrent" | "serial"): Pr
return [await processCheckoutWorker(requests[0])];
}

return Promise.all(requests.map((request) => processCheckoutWorker(request)));
const settled = await Promise.allSettled(requests.map((request) => processCheckoutWorker(request)));

const hardFailure = settled.find(
(result) =>
result.status === "rejected" &&
!(result.reason instanceof Error && result.reason.message.startsWith("OutOfStock:"))
);
Comment on lines +19 to +23
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Copilot AI Apr 19, 2026

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The OutOfStock detection here relies on parsing Error.message with startsWith("OutOfStock:"). This is brittle (message wording changes, wrapping, localization) and couples submit-order to reserve-stock’s string format. Prefer a typed error (e.g., class OutOfStockError extends Error { sku }) or an error code property so callers can branch reliably without string matching.

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if (hardFailure && hardFailure.status === "rejected") {
throw hardFailure.reason;
}

return settled.flatMap((result) => (result.status === "fulfilled" ? [result.value] : []));
Comment on lines +17 to +29
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Copilot AI Apr 19, 2026

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runCheckoutRaceScenario now returns only fulfilled results in concurrent mode, which can make the returned array shorter than the requests array. Since this function is exported and used by the server/script, consider returning a structure that preserves per-request outcomes (e.g., { successes, failures } or an array of discriminated union results) so callers can distinguish “one succeeded, one OutOfStock” from other scenarios instead of silently dropping failures.

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};
9 changes: 7 additions & 2 deletions demo_app/src/inventory/reserve-stock.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,11 @@ export const reserveStock = async (sku: string, quantity: number, requestId: str
await delay(25);

const record = getInventoryRecord(sku);

if (record.available < quantity) {
throw new Error(`OutOfStock: ${sku}`);
}

record.available -= quantity;
record.snapshotVersion += 1;

Expand All @@ -29,8 +34,8 @@ export const reserveStock = async (sku: string, quantity: number, requestId: str
}

return {
reservationToken: `res_${requestId}_${snapshot.snapshotVersion}`,
snapshotVersion: snapshot.snapshotVersion,
reservationToken: `res_${requestId}_${record.snapshotVersion}`,
snapshotVersion: record.snapshotVersion,
availableAfter: record.available
};
};