Exposes source maps to dynamic Assetic routes in debug mode

AssetManager.php

<?php

namespace my\TestBundle\Assetic;

use Assetic\Factory\LazyAssetManager;

/**
 * Overridden asset manager that exposes source maps referenced in CSS and JS
 */
class AssetManager extends LazyAssetManager {
    
    
    public function load(){
        parent::load();
        // skipping for production asset dump
        // would be preferable to grab assetic.user_controller, but no container access.
        if( ! $this->isDebug() ){
            return;
        }
        // add additional assets linked to those already found
        $deps = array();
        // find each leaf asset that may have a sourcemapping url
        foreach( $this->getNames() as $name ) {
            $assets = $this->get($name);
            $formula = $this->getFormula($name);
            foreach( $assets as $pos => $asset ){
                $ext = pathinfo($asset->getSourcePath(),PATHINFO_EXTENSION);
                if( 'js' !== $ext && 'css' !== $ext ){
                    continue 2;
                }    
                // have full path to original JS or CSS file
                $path = $asset->getSourceRoot().'/'.$asset->getSourcePath();
                $text = file_get_contents( $path );
                if( ! preg_match('/#\s*sourceMappingURL\s*=\s*([^\s\*]+)/', $text, $r ) ){
                    continue;
                }
                // sourcemap url is relative to source file location
                $fdir = dirname($path);
                $vdir = dirname($formula[2]['output']);
                $deps[ static::mapPath( $vdir, $r[1] ) ] = $fpath = $fdir.'/'.$r[1];
                // handle sources that map depends upon
                $json = file_get_contents( $fpath );
                $data = json_decode( $json, true );
                foreach( $data['sources'] as $sourcepath ){
                    // source assumed to be relative to map location, but tollerate if not found
                    if( file_exists( $fpath = $fdir.'/'.$sourcepath ) ){
                        $deps[ static::mapPath( $vdir, $sourcepath ) ] = $fpath;
                    }
                }
            }
        }
        // Add additional assets to lazy asset manager, will result in dynamic routes creating
        foreach( $deps as $vpath => $fpath ){
            $key = md5( $vpath );
            $this->setFormula( $key, array (
                array( $fpath ), // <- single map file asset
                array(),         // <- no filters
                array ( 
                    'output' => $vpath, // <- controller pattern placeholder
                    'combine' => true,  // <- prevents multiple routes for single asset
                ),
            ) );
        }
    }



    /**
     * utility maps a relative path to an absolute one, based on a base path
     * @param string base path e.g. "/some/location"
     * @param string relatve path, e.g. "../thing"
     * @return string absolute path, e.g. "/some/thing"
     */
    private static function mapPath( $base, $relative ){
        $absolute = explode('/', $base );
        $relative = explode('/', $relative);
        while( $relative && $absolute ){
            $next = array_shift($relative);
            if( '.' === $next ){
                // ignore
            }
            else if( '..' === $next ){
                array_pop( $absolute );
            }
            else {
                $absolute[] = $next;
            }
        }
        return implode('/',$absolute);
    }
    
    
}