Piwik\AssetManager\UIAssetMerger\StylesheetUIAssetMerger::getMergedAssets PHP Method

    protected function getMergedAssets()
    {
        // note: we're using setImportDir on purpose (not addImportDir)
        $this->lessCompiler->setImportDir(PIWIK_USER_PATH);
        $concatenatedAssets = $this->getConcatenatedAssets();
        $this->lessCompiler->setFormatter('classic');
        $compiled = $this->lessCompiler->compile($concatenatedAssets);
        foreach ($this->cssAssetsToReplace as $asset) {
            // to fix #10173
            $cssPath = $asset->getAbsoluteLocation();
            $cssContent = $this->processFileContent($asset);
            $compiled = str_replace($this->getCssStatementForReplacement($cssPath), $cssContent, $compiled);
        }
        $this->mergedContent = $compiled;
        $this->cssAssetsToReplace = array();
        return $compiled;
    }