fix: load app function only once when using createNodeMiddleware (#1432)

src/create-node-middleware.ts

@@ -1,7 +1,6 @@
-import { RequestListener, IncomingMessage, ServerResponse } from "http";
+import { RequestListener } from "http";
 
 import { Deprecation } from "deprecation";
-import { NextFunction } from "express";
 
 import { ApplicationFunction } from "./types";
 import { MiddlewareOptions } from "./types";
@@ -10,11 +9,6 @@ export function createNodeMiddleware(
   appFn: ApplicationFunction,
   { probot, Probot }: MiddlewareOptions
 ): RequestListener {
-  return (
-    request: IncomingMessage,
-    response: ServerResponse,
-    next?: NextFunction
-  ) => {
   if (Probot) {
     probot = new Probot();
     probot.log.warn(
@@ -25,6 +19,6 @@ export function createNodeMiddleware(
   }
 
   probot.load(appFn);
-    probot.webhooks.middleware(request, response, next);
-  };
+
+  return probot.webhooks.middleware;
 }

test/create-node-middleware.test.ts

@@ -1,4 +1,4 @@
-import { createServer } from "http";
+import { createServer, IncomingMessage, ServerResponse } from "http";
 import Stream from "stream";
 
 import pino from "pino";
@@ -6,7 +6,7 @@ import getPort from "get-port";
 import got from "got";
 import { sign } from "@octokit/webhooks";
 
-import { createNodeMiddleware, createProbot } from "../src";
+import { createNodeMiddleware, createProbot, Probot } from "../src";
 import { ApplicationFunction } from "../src/types";
 
 const APP_ID = "1";
@@ -75,4 +75,19 @@ describe("createNodeMiddleware", () => {
 
     server.close();
   });
+
+  test("loads app only once", async () => {
+    let counter = 0;
+    const appFn = () => {
+      counter++;
+    };
+    const middleware = createNodeMiddleware(appFn, {
+      probot: new Probot(),
+    });
+
+    middleware({} as IncomingMessage, { end() {} } as ServerResponse);
+    middleware({} as IncomingMessage, { end() {} } as ServerResponse);
+
+    expect(counter).toEqual(1);
+  });
 });

test/deprecations.test.ts

@@ -1,5 +1,6 @@
 import Stream from "stream";
 import { join } from "path";
+import { IncomingMessage, ServerResponse } from "http";
 
 import { Webhooks } from "@octokit/webhooks";
 import pino from "pino";
@@ -13,7 +14,6 @@ import {
   getOptions,
   createNodeMiddleware,
 } from "../src";
-import { IncomingMessage, ServerResponse } from "http";
 
 const pushEvent = require("./fixtures/webhook/push.json");