feat: add validateResponse()

src/problemResponse.ts

@@ -13,6 +13,7 @@ import type {
 } from 'aws-lambda'
 import { aProblem } from './aProblem.js'
 import { ValidationFailedError } from './validateInput.js'
+import { ResponseValidationFailedError } from './validateResponse.js'
 
 export class ProblemDetailError extends Error {
 	public readonly problem: Static<typeof ProblemDetail>
@@ -40,6 +41,12 @@ export const problemResponse = (): MiddlewareObj<
 				status: HttpStatusCode.BAD_REQUEST,
 				detail: formatTypeBoxErrors(req.error.errors),
 			})
+		} else if (req.error instanceof ResponseValidationFailedError) {
+			req.response = aProblem({
+				title: 'Response validation failed',
+				status: HttpStatusCode.INTERNAL_SERVER_ERROR,
+				detail: formatTypeBoxErrors(req.error.errors),
+			})
 		} else if (req.error instanceof ProblemDetailError) {
 			req.response = aProblem(req.error.problem)
 		} else {

src/validateInput.ts

@@ -1,4 +1,7 @@
-import { validateWithTypeBox } from '@hello.nrfcloud.com/proto'
+import {
+	formatTypeBoxErrors,
+	validateWithTypeBox,
+} from '@hello.nrfcloud.com/proto'
 import type { MiddlewareObj } from '@middy/core'
 import type { Static, TSchema } from '@sinclair/typebox'
 import type { ValueError } from '@sinclair/typebox/compiler'
@@ -11,8 +14,8 @@ import { tryAsJSON } from './tryAsJSON.js'
 
 export class ValidationFailedError extends Error {
 	public readonly errors: ValueError[]
-	constructor(errors: ValueError[]) {
-		super('Validation failed')
+	constructor(errors: ValueError[], message = 'Validation failed') {
+		super(message)
 		this.errors = errors
 		this.name = 'ValidationFailedError'
 	}
@@ -50,7 +53,10 @@ export const validateInput = <Schema extends TSchema>(
 				console.debug(
 					`[validateInput]`,
 					`Input not valid`,
-					JSON.stringify(maybeValidInput.errors),
+					JSON.stringify({
+						input,
+						errors: formatTypeBoxErrors(maybeValidInput.errors),
+					}),
 				)
 				throw new ValidationFailedError(maybeValidInput.errors)
 			}

src/validateResponse.spec.ts

@@ -0,0 +1,28 @@
+import middy from '@middy/core'
+import { Type } from '@sinclair/typebox'
+import type { Context } from 'aws-lambda'
+import assert from 'node:assert'
+import { describe, it } from 'node:test'
+import {
+	ResponseValidationFailedError,
+	validateResponse,
+} from './validateResponse.js'
+
+void describe('validateResponse()', () => {
+	void it('should validate the response', async () =>
+		assert.equal(
+			await middy()
+				.use(validateResponse(Type.Boolean({ title: 'A boolean' })))
+				.handler(async () => true)('Some event', {} as Context),
+			true,
+		))
+
+	void it('should throw an Error in case the response is invalid', async () =>
+		assert.rejects(
+			async () =>
+				middy()
+					.use(validateResponse(Type.Boolean()))
+					.handler(async () => 42)('Some event', {} as Context),
+			ResponseValidationFailedError,
+		))
+})

src/validateResponse.ts

@@ -0,0 +1,39 @@
+import {
+	formatTypeBoxErrors,
+	validateWithTypeBox,
+} from '@hello.nrfcloud.com/proto'
+import type middy from '@middy/core'
+import type { TSchema } from '@sinclair/typebox'
+import type { ValueError } from '@sinclair/typebox/errors'
+import { ValidationFailedError } from './validateInput.js'
+
+export class ResponseValidationFailedError extends ValidationFailedError {
+	constructor(errors: ValueError[]) {
+		super(errors, 'Response validation failed')
+		this.name = 'ResponseValidationFailedError'
+	}
+}
+
+export const validateResponse = <ResponseSchema extends TSchema>(
+	schema: ResponseSchema,
+): middy.MiddlewareObj => {
+	const validator = validateWithTypeBox(schema)
+	return {
+		after: async (req) => {
+			const maybeValid = validator(req.response)
+			if ('errors' in maybeValid) {
+				console.error(
+					`[validateResponse]`,
+					`Response validation failed`,
+					JSON.stringify({
+						response: req.response,
+						errors: formatTypeBoxErrors(maybeValid.errors),
+					}),
+				)
+				throw new ResponseValidationFailedError(maybeValid.errors)
+			}
+			console.debug(`[validateResponse]`, `Response is`, schema.title)
+			return undefined
+		},
+	}
+}