AssetConverter.php
protected function buildResult($asset, $dotPos = null, $resultSuffix = null)
    {
        if ($dotPos === null) {
            if (($dotPos = strrpos($asset, '.')) === false) {
                return $asset;
            }
        }

        $divider = ($this->compress === true) ? '-m' : '-';
        $suffix = ($resultSuffix !== null) ? $divider . (string)$resultSuffix . '.' . self::OUTPUT_EXT : '.' . self::OUTPUT_EXT;

        return substr($asset, 0, $dotPos) . $suffix;
    }
protected function buildResult($asset, $dotPos = null, $resultSuffix = null)
    {
        if ($dotPos === null) {
            if (($dotPos = strrpos($asset, '.')) === false) {
                return $asset;
            }
        }

        $divider = ($this->compress === true) ? '-m' : '-';
        $suffix = ($resultSuffix !== null) ? $divider . (string)$resultSuffix . '.' . self::OUTPUT_EXT : '.' . self::OUTPUT_EXT;

        return substr($asset, 0, $dotPos) . $suffix;
    }
Builds the result file name

@param string $asset the asset file path, relative to $basePath
@param int $dotPos the strrpos position of filename-extension dot
@param mixed $resultSuffix Suffix result css filename
@return string the converted asset file path, relative to $basePath.