feat: object-syntax event handlers (#485)

Co-authored-by: Pooya Parsa <[email protected]>

src/event/utils.ts

@@ -3,12 +3,18 @@ import type {
   LazyEventHandler,
   EventHandlerRequest,
   EventHandlerResponse,
+  EventHandlerObject,
 } from "../types";
+import type { H3Event } from "./event";
 
 export function defineEventHandler<
   Request extends EventHandlerRequest = EventHandlerRequest,
-  Response = any,
->(handler: EventHandler<Request, Response>): EventHandler<Request, Response>;
+  Response = EventHandlerResponse,
+>(
+  handler:
+    | EventHandler<Request, Response>
+    | EventHandlerObject<Request, Response>,
+): EventHandler<Request, Response>;
 // TODO: remove when appropriate
 // This signature provides backwards compatibility with previous signature where first generic was return type
 export function defineEventHandler<
@@ -26,10 +32,41 @@ export function defineEventHandler<
 export function defineEventHandler<
   Request extends EventHandlerRequest = EventHandlerRequest,
   Response = EventHandlerResponse,
->(handler: EventHandler<Request, Response>): EventHandler<Request, Response> {
-  handler.__is_handler__ = true;
-  return handler;
+>(
+  handler:
+    | EventHandler<Request, Response>
+    | EventHandlerObject<Request, Response>,
+): EventHandler<Request, Response> {
+  // Function Syntax
+  if (typeof handler === "function") {
+    return Object.assign(handler, { __is_handler__: true });
+  }
+  // Object Syntax
+  const _handler: EventHandler<Request, any> = (event) => {
+    return _callHandler(event, handler);
+  };
+  return Object.assign(_handler, { __is_handler__: true });
+}
+
+async function _callHandler(event: H3Event, handler: EventHandlerObject) {
+  if (handler.before) {
+    for (const hook of handler.before) {
+      await hook(event);
+      if (event.handled) {
+        return;
+      }
+    }
+  }
+  const body = await handler.handler(event);
+  const response = { body };
+  if (handler.after) {
+    for (const hook of handler.after) {
+      await hook(event, response);
+    }
+  }
+  return response.body;
 }
+
 export const eventHandler = defineEventHandler;
 
 export function isEventHandler(input: any): input is EventHandler {

src/types.ts

@@ -62,6 +62,18 @@ export interface EventHandler<
   (event: H3Event<Request>): Response;
 }
 
+export type EventHandlerObject<
+  Request extends EventHandlerRequest = EventHandlerRequest,
+  Response extends EventHandlerResponse = EventHandlerResponse,
+> = {
+  handler: EventHandler<Request, Response>;
+  before?: ((event: H3Event<Request>) => void | Promise<void>)[];
+  after?: ((
+    event: H3Event<Request>,
+    response: { body?: Response },
+  ) => void | Promise<void>)[];
+};
+
 export type LazyEventHandler = () => EventHandler | Promise<EventHandler>;
 
 export type RequestHeaders = { [name: string]: string | undefined };

test/types.test-d.ts

@@ -11,6 +11,29 @@ import {
 
 describe("types", () => {
   describe("eventHandler", () => {
+    it("object syntax definitions", async () => {
+      const handler = eventHandler({
+        before: [
+          (event) => {
+            expectTypeOf(event).toEqualTypeOf<H3Event>();
+          },
+        ],
+        async handler(event) {
+          expectTypeOf(event).toEqualTypeOf<H3Event>();
+
+          const body = await readBody(event);
+          // TODO: Default to unknown in next major version
+          expectTypeOf(body).toBeAny();
+
+          return {
+            foo: "bar",
+          };
+        },
+      });
+      expectTypeOf(await handler({} as H3Event)).toEqualTypeOf<{
+        foo: string;
+      }>();
+    });
     it("return type (inferred)", () => {
       const handler = eventHandler(() => {
         return {