Installing Packages in Symfony using Flex and Packs

Explanation of installing packages in Symfony using Flex and Packs.

Flex

Package is a ready-to-use functionality that adds new features to simplify development process.
In Symfony, packages are called bundles and are installed via Composer.

In order for bundle to work, it needs to be attached to framework. This usually requires doing some extra work - adding a bundle class in config/bundles.php and adding a config file in config/packages/*.yaml and possibly some others.

In order for bundle to automatically attach after installation, plugin for Composer called Flex was created.
Flex after installing bundle executes recipes, that is instructions for automating attachment and configuration of bundle in Symfony. Executed recipes are written to symfony.lock file.

There are two recipe repositories: main and contributor.
Main repository contains quality recipes for popular bundles.
Contributor repository contains recipes for the rest of bundles developed by community.

Bundle installation example using Flex

For example, you need to install logger (Monolog Bundle by default)

composer require logger

As a result, the following actions will be performed:

• Added class Symfony\Bundle\MonologBundle\MonologBundle::class to config/bundles.php file;

<?php

return [
    Symfony\Bundle\FrameworkBundle\FrameworkBundle::class => ['all' => true],
    Symfony\Bundle\MonologBundle\MonologBundle::class => ['all' => true],
];

• Added configuration file config/packages/monolog.yaml;

when@dev:
    monolog:
        handlers:
            main:
                type: stream
                path: "%kernel.logs_dir%/%kernel.environment%.log"
                level: debug
                channels: ["!event"]
            # uncomment to get logging in your browser
            # you may have to allow bigger header sizes in your Web server configuration
            #firephp:
            #    type: firephp
            #    level: info
            #chromephp:
            #    type: chromephp
            #    level: info
            console:
                type: console
                process_psr_3_messages: false
                channels: ["!event", "!doctrine", "!console"]

• Added executed recipe to symfony.lock;

"symfony/monolog-bundle": {
        "version": "3.8",
        "recipe": {
            "repo": "github.com/symfony/recipes",
            "branch": "main",
            "version": "3.7",
            "ref": "213676c4ec929f046dfde5ea8e97625b81bc0578"
        },
        "files": [
            "config/packages/monolog.yaml"
        ]
    },

Packs

Pack is a Composer package that contains a set of dependencies (packages). Pack is used to install all packages at once with one command, rather than individually for each package.
Once installed, composer.json will list the full set of packages, not the pack itself.

For example, let's install debug pack:

composer require --dev debug

As a result, these bundles will be written in composer.json:

"require-dev": {
    "symfony/debug-bundle": "6.1.*",
    "symfony/stopwatch": "6.1.*",
    "symfony/web-profiler-bundle": "6.1.*"
}