Edit composer dependencies "inline" while developing

Have a PHP project, and want to re-use some classes in a new project. Moving them to their own repository and turning them into a Composer dependency is a clean way to do that. If hosted on GitHub/BitBucket, it's even quite simple to publish the package on Packagist with automatic updates based on git tags. However, if still heavily developing both the project and the dependency, the round trip through repo/packagist is a pain.

But today I discovered there's an option called --prefer-source which seems to solve most of this pain. And here's a basic note-to-self on how to get that to work...

0. Make sure dependency is a composer dependency

// Dependency composer.json
{
  "name": "my/package",
  "autoload": {
    "psr-4": { "": "src/" }
  }
}

1. Add dependency repo and package to root project

// Root project composer.json
{
  "repositories": [
    { "type": "vcs", "url": "https://github.com/username/my-project" }
  ],
  "require": {
    "my/project": "dev-master"
  }
}

2. Run update with --prefer-source

$ composer require my/package dev-master --prefer-source

We should now have the package downloaded and, more importantly, if you check ./vendor/my/package it should have the .git directory, meaning you can make changes there directly, and commit them when you're happy... Our other root project(s) depending on it should then get the update from the source repository after an easy composer update. 👍