Using Symfony Flex to Manage Symfony Applications

3.3 version

Using Symfony Flex to Manage Symfony Applications

Symfony Flex is the new way to install and manage Symfony applications. Flex is not a new Symfony version, but a tool that replaces and improves the Symfony Installer and the Symfony Standard Edition.

Symfony Flex automates the most common tasks of Symfony applications, like installing and removing bundles and other Composer dependencies. Symfony Flex works for Symfony 3.3 and higher. Starting from Symfony 4.0, Flex should be used by default, but it is still optional.

How Does Flex Work

Symfony Flex is a Composer plugin that modifies the behavior of the require, update, and remove commands. When installing or removing dependencies in a Flex-enabled application, Symfony can perform tasks before and after the execution of Composer tasks.

Consider the following example:

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$ cd my-project/
$ composer require mailer

If you execute that command in a Symfony application which doesn't use Flex, you'll see a Composer error explaining that mailer is not a valid package name. However, if the application has Symfony Flex installed, that command ends up installing and enabling the SwiftmailerBundle, which is the best way to integrate Swiftmailer, the official mailer for Symfony applications.

When Symfony Flex is installed in the application and you execute composer require, the application makes a request to the Symfony Flex server before trying to install the package with Composer.

  • If there's no information about that package, the Flex server returns nothing and the package installation follows the usual procedure based on Composer;
  • If there's special information about that package, Flex returns it in a file called a "recipe" and the application uses it to decide which package to install and which automated tasks to run after the installation.

In the above example, Symfony Flex asks about the mailer package and the Symfony Flex server detects that mailer is in fact an alias for SwiftmailerBundle and returns the "recipe" for it.

Flex keeps tracks of the recipes it installed in a symfony.lock file, which must be committed to your code repository.

Symfony Flex Recipes

Recipes are defined in a manifest.json file and can contain any number of other files and directories. For example, this is the manifest.json for SwiftmailerBundle:

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{
    "bundles": {
        "Symfony\\Bundle\\SwiftmailerBundle\\SwiftmailerBundle": ["all"]
    },
    "copy-from-recipe": {
        "config/": "%CONFIG_DIR%/"
    },
    "env": {
        "MAILER_URL": "smtp://localhost:25?encryption=&auth_mode="
    },
    "aliases": ["mailer", "mail"]
}

The aliases option allows Flex to install packages using short and easy to remember names (composer require mailer vs composer require symfony/swiftmailer-bundle). The bundles option tells Flex in which environments this bundle should be enabled automatically (all in this case). The env option makes Flex to add new environment variables to the application. Finally, the copy-from-recipe option allows the recipe to copy files and directories into your application.

The instructions defined in this manifest.json file are also used by Symfony Flex when uninstalling dependencies (e.g. composer remove mailer) to undo all changes. This means that Flex can remove the SwiftmailerBundle from the application, delete the MAILER_URL environment variable and any other file and directory created by this recipe.

Symfony Flex recipes are contributed by the community and they are stored in two public repositories:

  • Main recipe repository, is a curated list of recipes for high quality and maintained packages. Symfony Flex only looks in this repository by default.

  • Contrib recipe repository, contains all the recipes created by the community. All of them are guaranteed to work, but their associated packages could be unmaintained. Symfony Flex ignores these recipes by default, but you can execute this command to start using them in your project:

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    $ cd your-project/
    $ composer config extra.symfony.allow-contrib true
    

Read the Symfony Recipes documentation to learn everything about how to create recipes for your own packages.

Using Symfony Flex in New Applications

Symfony has published a new "skeleton" project, which is a minimal Symfony project recommended to create new applications. This "skeleton" already includes Symfony Flex as a dependency. This means you can create a new Flex-enabled Symfony application by executing the following command:

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$ composer create-project symfony/skeleton my-project

Note

The use of the Symfony Installer to create new applications is no longer recommended since Symfony 3.3. Use the Composer create-project command instead.

Upgrading Existing Applications to Flex

Using Symfony Flex is optional, even in Symfony 4, where Flex will be used by default. However, Flex is so convenient and improves your productivity so much that it's strongly recommended to upgrade your existing applications to it.

The only caveat is that Symfony Flex requires that applications use the following directory structure, which is the same used by default in Symfony 4:

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your-project/
├── config/
│   ├── bundles.php
│   ├── packages/
│   ├── routes.yaml
│   └── services.yaml
├── public/
│   └── index.php
├── src/
│   ├── ...
│   └── Kernel.php
├── templates/
└── vendor/

This means that installing the symfony/flex dependency in your application is not enough. You must also upgrade the directory structure to the one shown above. There's no automatic tool to make this upgrade, so you must follow these manual steps:

  1. Create a new empty Symfony application (composer create-project symfony/skeleton my-project-flex)
  2. Merge the require and require-dev dependencies defined in your original project's composer.json file to the composer.json file of the new project (don't copy the symfony/symfony dependency, but add the relevant components you are effectively using in your project).
  3. Install the dependencies in the new project executing composer install. This will make Symfony Flex generate all the configuration files in config/packages/
  4. Review the generated config/packages/*.yaml files and make any needed changes according to the configuration defined in the app/config/config_*.yml file of your original project. Beware that this is the most time-consuming and error-prone step of the upgrade process.
  5. Move the original parameters defined in app/config/parameters.*.yml to the new config/services.yaml and .env files depending on your needs.
  6. Move the original source code from src/{App,...}Bundle/ to src/ and update the namespaces of every PHP file to be App\... (advanced IDEs can do this automatically).
  7. Move the original templates from app/Resources/views/ to templates/ and app/Resources/translations to translations/. There may be a few other files you need to move into a new location.
  8. Make any other change needed by your application. For example, if your original web/app_*.php front controllers were customized, add those changes to the new public/index.php controller.

This work, including the code samples, is licensed under a Creative Commons BY-SA 3.0 license.