This would allow us to add a seamless "Open in Compass" button from the Atlas Connect dialog. Aggregation of my notes for protocol handlers for "mongodb://" and "compass://".

—

Introduction

Protocol handlers are also sometimes referred to as custom URL schemes. For an excellent overview, please read this excellent blog post: How To Create Your Own URL Scheme.

Spotify spotify://, iTunes itmms:// and Intercom intercom:// are just a few examples of protocol handlers in action you may have encountered in the past. If you've ever seen the "External Protocol Request" dialog in Chrome, you've used protocol handlers:

User experience

Atlas short-term

Allows for clicking on mongodb://localhost:27017 -> open compass with connect form pre-filled.

Atlas and docs long-term

See elastic' view in console on all code blocks: https://www.elastic.co/guide/en/elasticsearch/reference/5.0/modules-scripting-painless.html

Use compass://<route> like Atom does for internal app routing instead of location hashes directly.

Implementation

There is a bit of a confusing division when it comes to protocol handlers in electron.

Three parts: OS registration, Electron registration, and protocol request handling

1. OS Registration

Differs by platform. Tells the OS clicks on mongodb:// in Chrome should be routed to Compass.

macOS

Specified at build time and registration is part of the OS's installation process. We already specify for this in Compass master:

{
  "protocols": [
    {"name": "MongoDB Protocol", "schemes": ["mongodb"]},
    {"name": "MongoDB Compass Protocol", "schemes": ["compass"]}
  ]
}

Windows

Unlike macOS, registration is not part of OS installation process. The application is responsible for protocol registration on first-run and on Windows that is done by updating the Windows Registry). For more details, see how webtorrent desktop does windows.

Linux

Like Windows, the application takes responsibility . On Linux, this is done by creating/updating the user's .desktop file. For more details, see how webtorrent desktop does linux

2. Electron registration

The protocol module in electron tells Electron that requests to the mongodb:// protocol in Compass should be routed to Compass.

3. Protocol request handling

app.on('open-file', <callback>) and app.on('open-url', <callback>)

See the Compass mongodb-protocol-handler branch.

var electron = require('electron');
var app = electron.app;
var program = require('commander');
var debug = require('nslog');

var open = {
  urls: [],
  files: []
};

app.on('will-finish-launching', function() {
  app.on('open-file', function(event, file) {
    event.preventDefault();
    open.files.push(file);
  });

  app.on('open-url', function(event, url) {
    event.preventDefault();
    open.urls.push(url);
  });
});

program
  .version(app.getVersion())
  .option('--dev', 'run in development mode');

program
  .command('[files...]')
  .action(function(files, opts) {
    debug('cli', {files: files, opts: opts});
  });

function parseCommandLine(argv) {
  return program.parse(argv);
}

var shouldQuit = app.makeSingleInstance(function(commandLine, workingDirectory) {
  return parseCommandLine(commandLine);
})

if (shouldQuit) {
  app.quit();
}

app.on('ready', function() {
  app.setAsDefaultProtocolClient('mongodb');
  app.setAsDefaultProtocolClient('compass');

  parseCommandLine(process.argv);
});

Making it all work as a single user flow

• Code to check if compass installed: See https://github.com/ismailhabib/custom-protocol-detection
• open.spotify.com
• Move Compass tour to .com
• when compass installed open browser to Compass tour like vscode (can also exchange analytics tokens)
• when not installed
• embed an open after install in URL to download which is saved via cookies
• Welcome page on .com can then check this cookie and show "still want to open mongodb://...?"

Further Reading

Web-based Protocol Handlers

• Mozilla Developer Network: Web-based protocol handlers
• Treehouse: Registering Protocol Handlers for Your Web Applications