Composer require local package

I've got a couple of libraries [Foo and Bar] that I'm developing in concert, but are still technically separate things. Previously I've just re-defined the autoloader to like "Foo\\": "../Foo/src", but now that I've added a Guzzle dependency to Foo, Bar flips it's lid because it's not one of its dependencies.

Directory structure:

/home/user/src/
    Foo/
        src/
            FooClient.php
        composer.json
    Bar/
        src/
            BarClient.php
        composer.json

Theoretical Autoload Statement: [in Bar/composer.json]

"require": {
    "local": "../Foo/composer.json"
}

Example code:

require('vendor/autoload.php');

$f = new \Bar\BarClient(new \Foo\FooClient());

How can I resolve this without setting up a local Composer repo? I want to maintain these as separate packages, just that one requires the other, and therefor processes the other's dependencies.

post-answer edit:

Thanks to infomaniac I've done the following:

Initialized the git repo:

cd ~/src/Foo && git init && echo -e "vendor\ncomposer.lock" > .gitignore && git add ./ && git commit -m "Initial Commit"

Added the composer config:

"require": {
    "sammitch/foo": "dev-master"
},
"repositories": [{
    "type": "vcs",
    "url": "/home/sammitch/src/Foo"
}],

And then composer update!

The way to link to a local, in-development package is to first add in your main project's composer.json a repository, like this:

"repositories": [
    {
        "type": "path",
        "url": "/full/or/relative/path/to/development/package"
    }
]

You also need to either have a version specified in your development package's composer.json or the way I do it is to require the package using @dev, like this:

composer require "vendorname/packagename @dev"

It should output:

- Installing vendor/packagename (dev-develop)
Symlinked from /full/or/relative/path/to/development/package

The @dev in the require command is important, composer uses this to pickup the source code and symlink it to your new package.

It's a stability flag added to the version constraint (see package link).

> These allow you to further restrict or expand the > stability of a package beyond the scope of the minimum-stability > setting.

The minimum-stability flags are:

> Available options (in order of stability) are dev, alpha, beta, RC, and stable.

You can use Composer's repositories feature

https://getcomposer.org/doc/05-repositories.md#path

{
  "repositories": [
    {
        "type": "path",
        "url": "../../packages/my-package"
    }
  ],
  "require": {
    "my/package": "*"
  }
}

Instead of using the http format, specify a file path on disk.

After spending some time, I finally understood the solution. Maybe it'll be useful for someone like me and will save you some time, so I've decided that I have to share it here.

Assuming that you have the following directory structure (relative to your project root directory):

composer.json
config
config/composition-root.php
local
local/bar-project
local/bar-project/composer.json
local/bar-project/src
local/bar-project/src/Bar.php
public
public/index.php
src
src/Foo.php

In this example you may see that the local folder is meant for nested projects of your company, e.g. bar-project. But you could configure any other layout, if you wish.

Each project has to have its own composer.json file, e.g. root composer.json and local/bar-project/composer.json. Then their contents would be as follows:

(root composer.json:)

{
  "name": "your-company/foo-project",
  "require": {
    "php": "^7",
    "your-company/bar-project": "@dev"
  },
  "autoload": {
    "psr-4": {
      "YourCompany\\FooProject\\": "src/"
    }
  },
  "repositories": [
    {
      "type": "path",
      "url": "local/bar-project"
    }
  ]
}

(local/bar-project/composer.json:)

{
  "name": "your-company/bar-project",
  "autoload": {
    "psr-4": {
      "YourCompany\\BarProject\\": "src/"
    }
  }
}

If, for example, you wish to locate each project in a separate sibling directory, as follows:

your-company
your-company/foo-project
your-company/foo-project/composer.json
your-company/foo-project/config
your-company/foo-project/config/composition-root.php
your-company/foo-project/public
your-company/foo-project/public/index.php
your-company/foo-project/src
your-company/foo-project/src/Foo.php
your-company/bar-project
your-company/bar-project/composer.json
your-company/bar-project/src
your-company/bar-project/src/Bar.php

- then you need to link to respective directory in repositories section:

  "repositories": [
    {
      "type": "path",
      "url": "../bar-project"
    }
  ]

After that don't forget to composer update (or even rm -rf vendor && composer update -v as the docs suggest)! Under the hood, composer will create a vendor/your-company/bar-project symlink that targets to local/bar-project (or ../bar-project respectively).

Assuming that your public/index.php is just a front controller, e.g.:

<?php
require_once __DIR__ . '/../config/composition-root.php';

Then your config/composition-root.php would be:

<?php

declare(strict_types=1);

use YourCompany\BarProject\Bar;
use YourCompany\FooProject\Foo;

require_once __DIR__ . '/../vendor/autoload.php';

$bar = new Bar();
$foo = new Foo($bar);
$foo->greet();