fix: Make probot receive support complex Probot apps (#1714)

The command `probot receive` fails to work when:

1. The Probot appFn is asynchronous
2. The Probot appFn requires `getRouter`

The command `probot run` works fine though with the same app.

This attempts to add support for these sort of Probot apps when calling `probot receive`.

src/bin/probot-receive.ts

@@ -1,5 +1,7 @@
 // Usage: probot receive -e push -p path/to/payload app.js
 
+import express, { Router } from "express";
+
 require("dotenv").config();
 
 import path from "path";
@@ -8,7 +10,7 @@ import program from "commander";
 import { getPrivateKey } from "@probot/get-private-key";
 import { getLog } from "../helpers/get-log";
 
-import { Probot } from "../";
+import { ApplicationFunctionOptions, Probot } from "../";
 import { resolveAppFunction } from "../helpers/resolve-app-function";
 
 async function main() {
@@ -101,10 +103,19 @@ async function main() {
     baseUrl: program.baseUrl,
   });
 
+  const expressApp = express();
+  const options: ApplicationFunctionOptions = {
+    getRouter: (path: string = "/") => {
+      const newRouter = Router();
+      expressApp.use(path, newRouter);
+      return newRouter;
+    },
+  };
+
   const appFn = await resolveAppFunction(
     path.resolve(process.cwd(), program.args[0])
   );
-  probot.load(appFn);
+  await probot.load(appFn, options);
 
   probot.log.debug("Receiving event", program.event);
   probot.receive({ name: program.event, payload, id: uuidv4() }).catch(() => {

src/probot.ts

@@ -11,6 +11,7 @@ import { ProbotOctokit } from "./octokit/probot-octokit";
 import { VERSION } from "./version";
 import {
   ApplicationFunction,
+  ApplicationFunctionOptions,
   DeprecatedLogger,
   Options,
   ProbotWebhooks,
@@ -104,14 +105,17 @@ export class Probot {
     return this.webhooks.receive(event);
   }
 
-  public async load(appFn: ApplicationFunction | ApplicationFunction[]) {
+  public async load(
+    appFn: ApplicationFunction | ApplicationFunction[],
+    options: ApplicationFunctionOptions = {}
+  ) {
     if (Array.isArray(appFn)) {
       for (const fn of appFn) {
         await this.load(fn);
       }
       return;
     }
 
-    return appFn(this, {});
+    return appFn(this, options);
   }
 }