function CssCollectionOptimizer::optimize

The cache file name is retrieved on a page load via a lookup variable that contains an associative array. The array key is the hash of the file names in $css while the value is the cache file name. The cache file is generated in two cases. First, if there is no file name value for the key, which will happen if a new file name has been added to $css or after the lookup variable is emptied to force a rebuild of the cache. Second, the cache file is generated if it is missing on disk. Old cache files are not deleted immediately when the lookup variable is emptied, but are deleted after a configurable period (

system . performance . stale_file_threshold;

) to ensure that files referenced by a cached page will still be available.

Overrides AssetCollectionOptimizerInterface::optimize

File

core/lib/Drupal/Core/Asset/CssCollectionOptimizer.php, line 91

Class

CssCollectionOptimizer

Optimizes CSS assets.

Namespace

Code

public function optimize(array $css_assets, array $libraries) {
    // Group the assets.
    $css_groups = $this->grouper
        ->group($css_assets);
    // Now optimize (concatenate + minify) and dump each asset group, unless
    // that was already done, in which case it should appear in
    // drupal_css_cache_files.
    // Drupal contrib can override this default CSS aggregator to keep the same
    // grouping, optimizing and dumping, but change the strategy that is used to
    // determine when the aggregate should be rebuilt (e.g. mtime, HTTPS …).
    $map = $this->state
        ->get('drupal_css_cache_files', []);
    $css_assets = [];
    foreach ($css_groups as $order => $css_group) {
        // We have to return a single asset, not a group of assets. It is now up
        // to one of the pieces of code in the switch statement below to set the
        // 'data' property to the appropriate value.
        $css_assets[$order] = $css_group;
        unset($css_assets[$order]['items']);
        switch ($css_group['type']) {
            case 'file':
                // No preprocessing, single CSS asset: just use the existing URI.
                if (!$css_group['preprocess']) {
                    $uri = $css_group['items'][0]['data'];
                    $css_assets[$order]['data'] = $uri;
                }
                else {
                    $key = $this->generateHash($css_group);
                    $uri = '';
                    if (isset($map[$key])) {
                        $uri = $map[$key];
                    }
                    if (empty($uri) || !file_exists($uri)) {
                        // Optimize each asset within the group.
                        $data = '';
                        $current_license = FALSE;
                        foreach ($css_group['items'] as $css_asset) {
                            // Ensure license information is available as a comment after
                            // optimization.
                            if ($css_asset['license'] !== $current_license) {
                                $data .= "/* @license " . $css_asset['license']['name'] . " " . $css_asset['license']['url'] . " */\n";
                            }
                            $current_license = $css_asset['license'];
                            $data .= $this->optimizer
                                ->optimize($css_asset);
                        }
                        // Per the W3C specification at
                        // http://www.w3.org/TR/REC-CSS2/cascade.html#at-import, @import
                        // rules must precede any other style, so we move those to the
                        // top. The regular expression is expressed in NOWDOC since it is
                        // detecting backslashes as well as single and double quotes. It
                        // is difficult to read when represented as a quoted string.
                        $regexp = <<<'REGEXP'
/@import\s*(?:'(?:\\'|.)*'|"(?:\\"|.)*"|url\(\s*(?:\\[\)\'\"]|[^'")])*\s*\)|url\(\s*'(?:\'|.)*'\s*\)|url\(\s*"(?:\"|.)*"\s*\)).*;/iU
REGEXP;
                        preg_match_all($regexp, $data, $matches);
                        $data = preg_replace($regexp, '', $data);
                        $data = implode('', $matches[0]) . (!empty($matches[0]) ? "\n" : '') . $data;
                        // Dump the optimized CSS for this group into an aggregate file.
                        $uri = $this->dumper
                            ->dump($data, 'css');
                        // Set the URI for this group's aggregate file.
                        $css_assets[$order]['data'] = $uri;
                        // Persist the URI for this aggregate file.
                        $map[$key] = $uri;
                        $this->state
                            ->set('drupal_css_cache_files', $map);
                    }
                    else {
                        // Use the persisted URI for the optimized CSS file.
                        $css_assets[$order]['data'] = $uri;
                    }
                    $css_assets[$order]['preprocessed'] = TRUE;
                }
                break;
            case 'external':
                // We don't do any aggregation and hence also no caching for external
                // CSS assets.
                $uri = $css_group['items'][0]['data'];
                $css_assets[$order]['data'] = $uri;
                break;
        }
    }
    return $css_assets;
}