evilissimo/design-by-contract
Analyze code to suggest and add Design by Contract specifications (preconditions, postconditions, invariants, semantic invariants) in any language. Trigger on: "Design by Contract", "DBC", "preconditions", "postconditions", "class invariants", "code contracts", "formal specifications", "document assumptions", "add contracts", "make this function safer", "define what this function guarantees", "add assertions to document behavior", Bertrand Meyer, Eiffel contracts, or when discussing invariants that should always hold. Do NOT skip for non-Eiffel code — DBC applies everywhere via assertions, type guards, properties.
92
90%
Does it follow best practices?
Impact
95%
1.05xAverage score across 5 eval scenarios
Passed
No known issues
task.mdevals/scenario-2/
Contract a Payment Webhook Boundary
Problem/Feature Description
A Node service receives payment webhook payloads from an external provider. Several production failures came from missing fields, unrecognized statuses, and handlers continuing after malformed payloads. Add contract-oriented documentation and enforcement at the boundary so downstream code can rely on a normalized event.
Output Specification
Produce webhook_contract_analysis.md, webhook.ts, and webhook_contract_tests.md showing expected valid and invalid cases.
Input Files
=============== FILE: webhook.ts ===============
type RawWebhook = any
export function handlePaymentWebhook(payload: RawWebhook) {
const eventId = payload.id
const amount = Number(payload.data.amount)
const status = payload.data.status
if (status === "paid") {
markInvoicePaid(payload.data.invoice_id, amount)
}
return { eventId, status }
}