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Developing an app

To develop a Probot app, you will first need a recent version of Node.js installed. Open a terminal and run node -v to verify that it is installed and is at least 8.3.0 or later. Otherwise, install the latest version.

Generating a new app

create-probot-app is the best way to start building a new app. It will generate a new app with everything you need to get started and run your app in production.

To get started, run one of these commands:

  • If you're using npm: $ npx create-probot-app my-first-app
  • or, if you're using Yarn: $ yarn create probot-app my-first-app

This will ask you a series of questions about your app, which should look something like this:

Let's create a Probot app!
? App name: my-first-app
? Description of app: A "Hello World" GitHub App built with Probot
? Author's full name: Katie Horne
? Author's email address: katie@auth0.com
? Homepage:
? GitHub user or org name: khorne3
? Repository name: my-first-app
created file: my-first-app/.env.example
created file: my-first-app/.gitignore
created file: my-first-app/.travis.yml
created file: my-first-app/LICENSE
created file: my-first-app/README.md
created file: my-first-app/app.json
created file: my-first-app/index.js
created file: my-first-app/package-lock.json
created file: my-first-app/package.json
created file: my-first-app/docs/deploy.md
Finished scaffolding files!

Installing Node dependencies!

Done! Enjoy building your Probot app!

The most important files note here are index.js, which is where the code for your app will go, and package.json, which makes this a standard npm module.

Configuring a GitHub App

To run your app in development, you will need to configure a GitHub App to deliver webhooks to your local machine.

  1. On your local machine, copy .env.example to .env.
  2. Go to smee.io and click Start a new channel. Set WEBHOOK_PROXY_URL in .env to the URL that you are redirected to.
  3. Create a new GitHub App with:
    • Webhook URL: Use your WEBHOOK_PROXY_URL from the previous step.
    • Webhook Secret: development
    • Permissions & events is located lower down the page and will depend on what data you want your app to have access to. Note: if, for example, you only enable issue events, you will not be able to listen on pull request webhooks with your app. However, for development we recommend enabling everything.
  4. Download the private key and move it to your project's directory. As long as it's in the root of your project, Probot will find it automatically regardless of the filename.
  5. Edit .env and set APP_ID to the ID of the app you just created. The App ID can be found in your app settings page here screen shot 2017-08-20 at 8 31 31 am

Installing the app on a repo

You'll need to create a test repository and install your app by clicking the "Install" button on the settings page of your app, e.g. https://github.com/apps/your-app

Running the app locally

Now you're ready to run the app on your local machine. Run npm run dev to start the server:

$ npm run dev

> my-app@1.0.0 dev /Users/z/Desktop/foo
> nodemon --exec "npm start"

[nodemon] 1.17.2
[nodemon] to restart at any time, enter `rs`
[nodemon] watching: *.*
[nodemon] starting `npm start`

> my-app@1.0.0 start /Users/z/Desktop/foo
> probot run ./index.js

Yay, the plugin was loaded!
18:11:55.838Z DEBUG Probot: Loaded plugin: ./index.js

The dev script will start your app using nodemon, which will watch for any files changes in your local development environment and automatically restart the server.

Other available scripts

  • $ npm start to start your app without watching files.
  • $ npm run lint to lint your code using standard.

Debugging

  1. Always run $ npm install and restart the server if package.json has changed.
  2. To turn on verbose logging, start server by running: $ LOG_LEVEL=trace npm start

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