feat(middlewares): use onError

This changes the validateInput() middleware to throw an error
instead of returning the response.

This allows for the corsOPTIONS() middleware to hook into
the error response, which is now handled by a generic
middleware which turns errors into Problem Detail responses
using aProblem()

BREAKING CHANGE: this changes the way validateInput() works

Author: coderbyheart

src/corsOPTIONS.ts

@@ -2,32 +2,37 @@ import type {
 	APIGatewayProxyEventV2,
 	APIGatewayProxyStructuredResultV2,
 } from 'aws-lambda'
-import type { MiddlewareObj } from '@middy/core'
+import type { MiddlewareObj, Request } from '@middy/core'
 import { corsHeaders } from './corsHeaders.js'
 
 export const corsOPTIONS = (
 	...allowedMethods: string[]
-): MiddlewareObj<
-	APIGatewayProxyEventV2,
-	APIGatewayProxyStructuredResultV2
-> => ({
-	before: async (req) => {
-		if (req.event.requestContext.http.method === 'OPTIONS') {
-			return {
-				statusCode: 200,
-				headers: corsHeaders(req.event, allowedMethods),
-			}
+): MiddlewareObj<APIGatewayProxyEventV2, APIGatewayProxyStructuredResultV2> => {
+	const setCorsHeaders = async (req: Request) => {
+		if (req.response === null) {
+			console.error(`[corsOPTIONS]`, `Response is null`)
+			return
 		}
-		return undefined
-	},
-	after: async (req) => {
-		if (req.response === null) return
 		req.response = {
 			...req.response,
 			headers: {
 				...req.response.headers,
 				...corsHeaders(req.event, allowedMethods),
 			},
 		}
-	},
-})
+	}
+	return {
+		before: async (req) => {
+			if (req.event.requestContext.http.method === 'OPTIONS') {
+				console.debug(`[corsOPTIONS]`, `Handling OPTIONS request`)
+				return {
+					statusCode: 200,
+					headers: corsHeaders(req.event, allowedMethods),
+				}
+			}
+			return undefined
+		},
+		after: setCorsHeaders,
+		onError: setCorsHeaders,
+	}
+}

src/problemResponse.ts

@@ -0,0 +1,50 @@
+import { formatTypeBoxErrors } from '@hello.nrfcloud.com/proto'
+import {
+	HttpStatusCode,
+	type ProblemDetail,
+} from '@hello.nrfcloud.com/proto/hello'
+import type { MiddlewareObj } from '@middy/core'
+import type { Static } from '@sinclair/typebox'
+import type {
+	APIGatewayProxyEventV2,
+	APIGatewayProxyStructuredResultV2,
+	Context,
+} from 'aws-lambda'
+import { aProblem } from './aProblem.js'
+import { ValidationFailedError } from './validateInput.js'
+
+export class ProblemDetailError extends Error {
+	public readonly problem: Static<typeof ProblemDetail>
+	constructor(problem: Static<typeof ProblemDetail>) {
+		super(problem.title)
+		this.problem = problem
+		this.name = 'ProblemDetailError'
+	}
+}
+
+export const problemResponse = (): MiddlewareObj<
+	APIGatewayProxyEventV2,
+	APIGatewayProxyStructuredResultV2,
+	Error,
+	Context
+> => ({
+	onError: async (req) => {
+		if (req.error instanceof ValidationFailedError) {
+			return aProblem({
+				title: 'Validation failed',
+				status: HttpStatusCode.BAD_REQUEST,
+				detail: formatTypeBoxErrors(req.error.errors),
+			})
+		}
+		if (req.error instanceof ProblemDetailError) {
+			return aProblem(req.error.problem)
+		}
+		return aProblem({
+			title:
+				req.error instanceof Error
+					? req.error.message
+					: 'Internal Server Error',
+			status: HttpStatusCode.INTERNAL_SERVER_ERROR,
+		})
+	},
+})

src/validateInput.ts

@@ -1,17 +1,22 @@
+import { 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'
 import type {
 	APIGatewayProxyEventV2,
 	APIGatewayProxyStructuredResultV2,
 	Context,
 } from 'aws-lambda'
-import type { MiddlewareObj } from '@middy/core'
-import type { Static, TSchema } from '@sinclair/typebox'
-import {
-	formatTypeBoxErrors,
-	validateWithTypeBox,
-} from '@hello.nrfcloud.com/proto'
-import { HttpStatusCode } from '@hello.nrfcloud.com/proto/hello'
 import { tryAsJSON } from './tryAsJSON.js'
-import { aProblem } from './aProblem.js'
+
+export class ValidationFailedError extends Error {
+	public readonly errors: ValueError[]
+	constructor(errors: ValueError[]) {
+		super('Validation failed')
+		this.errors = errors
+		this.name = 'ValidationFailedError'
+	}
+}
 
 export const validateInput = <Schema extends TSchema>(
 	schema: Schema,
@@ -47,11 +52,7 @@ export const validateInput = <Schema extends TSchema>(
 					`Input not valid`,
 					JSON.stringify(maybeValidInput.errors),
 				)
-				return aProblem({
-					title: 'Validation failed',
-					status: HttpStatusCode.BAD_REQUEST,
-					detail: formatTypeBoxErrors(maybeValidInput.errors),
-				})
+				throw new ValidationFailedError(maybeValidInput.errors)
 			}
 			console.debug(`[validateInput]`, `Input valid`)
 			req.context.validInput = maybeValidInput.value