Merge branch 'main' into develop

Author: willfarrell

packages/core/index.d.ts

@@ -140,9 +140,13 @@ declare type UseFn<
 	TErr = Error,
 	TContext extends LambdaContext = LambdaContext,
 	TInternal extends Record<string, unknown> = {},
-> = <TMiddleware extends MiddlewareObj<any, any, Error, any, any>>(
-	middlewares: TMiddleware | TMiddleware[],
-) => TMiddleware extends MiddlewareObj<
+> = <
+	TMiddlewares extends
+		| MiddlewareObj<any, any, Error, any, any>
+		| MiddlewareObj<any, any, Error, any, any>[],
+>(
+	middlewares: TMiddlewares,
+) => TMiddlewares extends MiddlewareObj<
 	infer TMiddlewareEvent,
 	any,
 	Error,
@@ -155,8 +159,22 @@ declare type UseFn<
 			TErr,
 			TMiddlewareContext & TContext,
 			TMiddlewareInternal & TInternal
-		> // always true
-	: never;
+		>
+	: TMiddlewares extends MiddlewareObj<
+				infer TMiddlewareEvent,
+				any,
+				Error,
+				infer TMiddlewareContext,
+				infer TMiddlewareInternal
+			>[]
+		? MiddyfiedHandler<
+				TEvent & TMiddlewareEvent,
+				TResult,
+				TErr,
+				TContext & TMiddlewareContext,
+				TInternal & TMiddlewareInternal
+			>
+		: never;
 
 declare type MiddlewareHandler<
 	THandler extends LambdaHandler<any, any>,

packages/core/index.test-d.ts

@@ -553,3 +553,17 @@ middy<unknown, string>()
 // @ts-expect-error!
 const s3MiddyHandler = middy().handler(s3Handler);
 expect(s3MiddyHandler).type.toBe<middy.MiddyfiedHandler<unknown, any>>();
+
+// Issue #1289 .use() does not intersect Typescript types appropriately for an array of middleware
+const middleware1 = { before: (req: middy.Request<{ foo: string }>) => {} };
+const middleware2 = { before: (req: middy.Request<{ bar: string }>) => {} };
+const handlerWithCombinedEvent = middy(lambdaHandler).use([
+	middleware1,
+	middleware2,
+]);
+expect(handlerWithCombinedEvent).type.toBe<
+	middy.MiddyfiedHandler<
+		APIGatewayProxyEvent & { foo: string } & { bar: string },
+		APIGatewayProxyResult
+	>
+>();