Create a UX bundle

composer.json file

Your composer.json file must have the symfony-ux keyword:

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{
    "keywords": ["symfony-ux"]
}

Assets location

Your assets must be located in one of the following directories, with a package.json file so Flex can handle it during install/update:

• /assets (recommended)
• /Resources/assets
• /src/Resources/assets

package.json file

Your package.json file must contain a symfony config with controllers defined, and also add required packages to the peerDependencies and importmap (the list of packages in importmap should be the same as the ones in peerDependencies):

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{
    "name": "@acme/feature",
    "version": "1.0.0",
    "symfony": {
        "controllers": {
            "slug": {
                "main": "dist/controller.js",
                "fetch": "eager",
                "enabled": true,
                "autoimport": {
                    "@acme/feature/dist/bootstrap4-theme.css": false,
                    "@acme/feature/dist/bootstrap5-theme.css": true
                }
            }
        },
        "importmap": {
            "@hotwired/stimulus": "^3.0.0",
            "slugify": "^1.6.5"
        }
    },
    "peerDependencies": {
        "@hotwired/stimulus": "^3.0.0",
        "slugify": "^1.6.5"
    }
}

In this case, the file located at [assets directory]/dist/controller.js will be exposed.

To use your controller in a template (e.g. one defined in your bundle) you can use it like this:

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<div
    {{ stimulus_controller('acme/feature/slug', { modal: 'my-value' }) }}
    {#
        will render:
        data-controller="acme--feature--slug"
        data-acme--feature--slug-modal-value="my-value"
    #}
>
    ...
</div>

Don't forget to add symfony/stimulus-bundle:^2.9 as a composer dependency to use Twig stimulus_* functions.

Each controller has a number of options in package.json file:

enabled:

Whether the controller should be enabled by default.

main:

Path to the controller file.

fetch:

How controller & dependencies are included when the page loads. Use eager (default) to make controller & dependencies included in the JavaScript that's downloaded when the page is loaded. Use lazy to make controller & dependencies isolated into a separate file and only downloaded asynchronously if (and when) the data-controller HTML appears on the page.

autoimport:

List of files to be imported with the controller. Useful e.g. when there are several CSS styles depending on the frontend framework used (like Bootstrap 4 or 5, Tailwind CSS...). The value must be an object with files as keys, and a boolean as value for each file to set whether the file should be imported.

Specifics for Asset Mapper

To make your bundle's assets work with AssetMapper, you must add the importmap config like above in your package.json file, and prepend some configuration to the container:

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namespace Acme\FeatureBundle;

use Symfony\Component\AssetMapper\AssetMapperInterface;
use Symfony\Component\DependencyInjection\ContainerBuilder;
use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
use Symfony\Component\HttpKernel\Bundle\AbstractBundle;

class AcmeFeatureBundle extends AbstractBundle
{
    public function prependExtension(ContainerConfigurator $configurator, ContainerBuilder $container): void
    {
        if (!$this->isAssetMapperAvailable($container)) {
            return;
        }

        $container->prependExtensionConfig('framework', [
            'asset_mapper' => [
                'paths' => [
                    __DIR__ . '/../assets/dist' => '@acme/feature-bundle',
                ],
            ],
        ]);
    }

    private function isAssetMapperAvailable(ContainerBuilder $container): bool
    {
        if (!interface_exists(AssetMapperInterface::class)) {
            return false;
        }

        // check that FrameworkBundle 6.3 or higher is installed
        $bundlesMetadata = $container->getParameter('kernel.bundles_metadata');
        if (!isset($bundlesMetadata['FrameworkBundle'])) {
            return false;
        }

        return is_file($bundlesMetadata['FrameworkBundle']['path'] . '/Resources/config/asset_mapper.php');
    }
}