Use composer ton install depedencies while creating custom WP plugin - wordpress

Question

I'm really new to composer and don't understand it well (yet).
Here's the thing :
I'm building a Wordpress plugin that needs external libraries.
Thoses libraries are FluentDOM and Selectors-Symfony for FluentDOM.
Both have installation instructions for Composer only :
FluentDOM :
FluentDOM is available on Packagist.org, just add the dependency to your composer.json.
{
"require" : {
"fluentdom/fluentdom": "5.x"
}
}
Selectors-Symfony :
composer require symfony/css-selector
My plugin path is /wordpress/wp-content/my-custom-plugin.
Should I write a composer.json file at the root of this directory, and what should be its content ?
Eventually, I would like install those depedencies in /wordpress/wp-content/my-custom-plugin/_inc/lib
Could anyone explain me how to do this ?
Thanks !

Answer 1

Well, I'd say that unless Wordpress starts supporting Composer (they don't officially at this time although Wordpress can be installed with Composer if you know what you're doing, first and foremost know the package name of it), you shouldn't think too much about using it for delivery of your plugin, meaning: If you use other software in your plugin, I think you have to bundle it inside your plugin, or it won't work.
It still will create issues like "Is the version of the library you are using compatible with the same library other plugins use?" and "How do you do autoloading?" correctly.
Internally, you could use Composer to manage these libraries just like you would do with any other project that uses Composer, with the minor difference that the released package of your plugin must include all these libraries and autoloaders you added - with Composer or something else.
Be warned that I basically don't know anything about how Wordpress people usually organize their stuff. Reading the discussion I linked to in the comment to your question, I get the impression that they have still a very long way to go, and that there is nobody actively behind it and promotes using Composer for dependency management because it also works the usual way, or it might break things.

Answer 2

Internally, you could use Composer to manage these libraries just like
you would do with any other project that uses Composer, with the minor
difference that the released package of your plugin must include all
these libraries and autoloaders you added - with Composer or something
else.
Thanks Sven, that is what I wanted to know.
I finally managed to do it.
Here is my step-by-step guide to install a dependency (here, fluentDOM) into /wordpress/wp-content/plugins/my-custom-plugin/_inc/php with the terminal and without having any composer.json at the start.
First, of course, you need to install Composer. As I will use it for php dependencies of my plugin, I will install it in my-custom-plugin/_inc/php.
(You could also install it at the root of your plugin and adjust following commands)
1/ Open Terminal and go to that directory :
cd /Applications/MAMP/htdocs/my-project/wordpress/wp-content/plugins/my-custom-plugin/_inc/php
2/ Install Composer :
curl -sS https://getcomposer.org/installer | php
Now I'm ready to use Composer in my-custom-plugin/_inc/php.
On the fluentDOM website, I see that the package I need to install is called fluentdom/fluentdom.
3/ So, let's install the package :
composer require fluentdom/fluentdom
If you need more informations about this package, the website packagist could be useful. It shows informations (version, dependencies), ... for composer packages. See fluentdom/fluentdom.
This installs fluentdom in the default composer directory /vendor and generates a composer.json file; which is nice to update dependencies later.
Here's the generated content:
{
"require": {
"fluentdom/fluentdom": "~5.2"
}
}
But we wanted our dependency to be installed into my-custom-plugin/_inc/php, not into my-custom-plugin/_inc/php/vendor !
4/ Let's edit composer.json, and set the default directory parameter vendor-dir to empty.
{
"require": {
"fluentdom/fluentdom": "~5.2"
},
"config": {
"vendor-dir": ""
}
}
5/ Delete the my-custom-plugin/_inc/php/vendor directory as we don't need it anymore.
6/ Now that we have a composer.json file, we just have to run
composer.phar install
Or
composer.phar update
... and the magic happens ! Done !!! We have the dependencies installed, and an autoload.php file generated.
7/ The last thing to do is to include the autoload.php in your plugin :
require_once( plugin_dir_path( __FILE__ ) . '_inc/php/autoload.php' );
This was the way to achieve it without having a composer.json file.
If you have your composer.json file ready, skip steps 3 to 5.
I also suggest to read this blog post : 5 features to know about Composer PHP.