VersionStrategy for using assets versioned with gulp-rev in Symfony

config.yml

framework:
    assets:
        version_strategy: app.assets.gulp_rev_version_strategy

GulpRevVersionStrategy.php

<?php

namespace AppBundle\Twig;

use Exception;
use Symfony\Component\Asset\VersionStrategy\VersionStrategyInterface;

class GulpRevVersionStrategy implements VersionStrategyInterface
{
    private $manifestFilename;

    private $manifestDir;

    private $paths = [];

    /**
     * VersionStrategy constructor.
     *
     * @param string $manifestDir
     * @param string $manifestFilename
     */
    public function __construct($manifestDir, $manifestFilename = 'rev-manifest.json')
    {
        $this->manifestFilename = $manifestFilename;
        $this->manifestDir = $manifestDir;
    }

    public function getVersion($path)
    {
        if (file_exists($path)) {
            return null;
        }

        $path = pathinfo($this->getAssetVersion($path));
        $filenameParts = explode('-', $path['filename']);

        // With gulp rev, the version is at the end of the filename so it will be the last item of the array
        return $filenameParts[count($filenameParts) - 1];
    }

    public function applyVersion($path)
    {
        return $this->getAssetVersion($path);
    }

    private function getAssetVersion($path)
    {
        // The twig extension is a singleton so we store the loaded content into a property to read it only once
        // @see https://knpuniversity.com/screencast/gulp/version-cache-busting#comment-2884388919
        if (count($this->paths) === 0) {
            $manifestPath = $this->manifestDir .'/'. $this->manifestFilename;$manifestPath = $this->manifestDir .'/'. $this->manifestFilename;
            
            if (!is_file($manifestPath)) {
                throw new Exception(
                    sprintf(
                        'Manifest file "%s" not found in path "%s". You can generate this file running gulp',
                        $this->manifestFilename, $this->manifestDir
                    )
                );
            }

            $this->paths = json_decode(file_get_contents($manifestPath), true);
        }


        // If a file exists, it doesn't have a version so we ignore it
        $fileExists = file_exists($path);
        $hasVersion = isset($this->paths[$path]);

        if (!$fileExists && !$hasVersion) {
            throw new Exception(sprintf('The file "%s" does not exist and there is no version file for it', $path));
        }

        return $hasVersion ? $this->paths[$path] : $path;
    }
}

services.yml

services:

    app.assets.gulp_rev_version_strategy:
        class: AppBundle\Twig\GulpRevVersionStrategy
        arguments: ["%kernel.root_dir%/Resources/assets"]
        public: false