src/ThemeManager/ThemeCollection.php
public function merge($items, $addPath = false)
    {
        $themesPaths = $this->getThemesPaths();
        /* @var $themeCollection $this */
        $themeCollection = parent::merge($items);

        $themeCollection->requiredFields = $this->requiredFields;
        $themeCollection->exceptionOnInvalid = $this->exceptionOnInvalid;

        if ($addPath !== false) {
            $themesPaths[] = realpath($addPath);
        }
        foreach ($themesPaths as $path) {
            $themeCollection->themesFolders[$path] = $path;
        }

        return $themeCollection;
    }
public function merge($items, $addPath = false)
    {
        $themesPaths = $this->getThemesPaths();
        /* @var $themeCollection $this */
        $themeCollection = parent::merge($items);

        $themeCollection->requiredFields = $this->requiredFields;
        $themeCollection->exceptionOnInvalid = $this->exceptionOnInvalid;

        if ($addPath !== false) {
            $themesPaths[] = realpath($addPath);
        }
        foreach ($themesPaths as $path) {
            $themeCollection->themesFolders[$path] = $path;
        }

        return $themeCollection;
    }
@param mixed          $items
@param string|bool $addPath

@return static