more complete middy middlewares with upgraded typing

packages/helpers/middify.ts

@@ -1,7 +1,66 @@
-import middy from "@middy/core";
+import middy, { MiddyfiedHandler } from "@middy/core";
 import middyJsonBodyParser from "@middy/http-json-body-parser";
-import type { Handler } from "aws-lambda";
+import cors from "@middy/http-cors";
+import validator from "@middy/validator";
+import { transpileSchema } from "@middy/validator/transpile";
+import httpErrorHandler from "@middy/http-error-handler";
+import httpEventNormalizer from "@middy/http-event-normalizer";
 
-export const middyfy = <TEvent, TResult>(handler: Handler<TEvent, TResult>) => {
-  return middy<TEvent, TResult>(handler).use(middyJsonBodyParser());
+import type {
+  APIGatewayProxyEvent as ProxyEvent,
+  APIGatewayProxyResult,
+  Context,
+  Handler as AWSHandler,
+} from "aws-lambda";
+import type { FromSchema } from "json-schema-to-ts";
+
+// Taken from https://github.com/middyjs/middy/issues/316#issuecomment-1013351805
+// Event is an APIGatewayProxyEvent with a typed body, pathParameters and queryStringParameters which depends on http-json-body-parser & json-schema-to-ts
+// queryStringParameters and multiValueQueryStringParameters is non-nullable as we use http-event-normalizer
+export interface Event<
+  TBody extends Record<string, unknown> | null,
+  TPathParameters extends Record<string, unknown> | null,
+  TQueryStringParameters extends Record<string, unknown> | null
+> extends Omit<
+    ProxyEvent,
+    "body" | "pathParameters" | "queryStringParameters"
+  > {
+  body: TBody extends Record<string, unknown> ? FromSchema<TBody> : null;
+  pathParameters: TPathParameters extends Record<string, unknown>
+    ? FromSchema<TPathParameters>
+    : null;
+  queryStringParameters: TQueryStringParameters extends Record<string, unknown>
+    ? FromSchema<TQueryStringParameters>
+    : null;
+  multiValueQueryStringParameters: NonNullable<
+    ProxyEvent["multiValueQueryStringParameters"]
+  >;
+}
+
+// We are making use of http-response-serializer
+interface Result extends Omit<APIGatewayProxyResult, "body"> {
+  body: string | Record<string, unknown>;
+}
+
+// Handler type which gives us proper types on our event based on TBody and TPathParameters which are JSON schemas
+export type CustomHandler<
+  TBody extends Record<string, unknown> | null = null,
+  TPathParameters extends Record<string, unknown> | null = null,
+  TQueryStringParameters extends Record<string, unknown> | null = null
+> = AWSHandler<Event<TBody, TPathParameters, TQueryStringParameters>, Result>;
+
+// TODO: find a way to remove the couple of `any` here. Validation and typing are still working though
+export const middyfy = (
+  handler: any,
+  schema: Record<string, unknown> | null = null
+): MiddyfiedHandler<Event<never, never, never>, Result, Error, Context> => {
+  const wrapper: any = middy(handler)
+    .use(middyJsonBodyParser())
+    .use(httpEventNormalizer());
+
+  if (schema) {
+    wrapper.use(validator({ eventSchema: transpileSchema(schema) }));
+  }
+
+  return wrapper.use(cors()).use(httpErrorHandler({}));
 };

packages/helpers/package.json

@@ -12,8 +12,12 @@
   },
   "dependencies": {
     "@middy/core": "^5.2.4",
+    "@middy/http-cors": "^5.2.4",
+    "@middy/http-error-handler": "^5.2.4",
+    "@middy/http-event-normalizer": "^5.2.4",
+    "@middy/http-json-body-parser": "^5.2.4",
     "@middy/util": "^5.2.4",
-    "@middy/http-json-body-parser": "^5.2.4"
+    "@middy/validator": "^5.2.4"
   },
   "devDependencies": {
     "@types/aws-lambda": "^8.10.133",

packages/helpers/response.ts

@@ -1,19 +1,3 @@
-import type {
-  APIGatewayProxyEvent,
-  APIGatewayProxyResult,
-  Handler,
-} from "aws-lambda";
-import type { FromSchema } from "json-schema-to-ts";
-
-export type ValidatedAPIGatewayProxyEvent<S extends object> = Omit<
-  APIGatewayProxyEvent,
-  "body"
-> & { body: FromSchema<S> };
-export type ValidatedEventAPIGatewayProxyEvent<S extends object> = Handler<
-  ValidatedAPIGatewayProxyEvent<S>,
-  APIGatewayProxyResult
->;
-
 export const formatJSONResponse = (response: Record<string, unknown>) => {
   return {
     statusCode: 200,