Magento 2: What is the `module` Attribute in `menu.xml` Files Used For?

Question

In Magento 2, when you add a menu item, you need to specify a module attribute (module="Magento_Backend" below)

<add id="Magento_Backend::system_currency" 
     title="Currency" 
     module="Magento_Backend" 
     sortOrder="30" 
     parent="Magento_Backend::stores"
     action="adminhtml/system_currency"         
     resource="Magento_CurrencySymbol::system_currency"
/>

What does the Magento system use this attribute for? i.e., why does the menu rendering need to know which module a Menu Item comes from?

Answer 1

From what I've seen the main reason is to be able to hide the menu item if the module output is disabled.

In app/code/Magento/Backend/Model/Menu/Item.php you can find the following function where $this->_moduleName represents the value of the module attribute of the menu:

public function isDisabled()
    {
        return !$this->_moduleManager->isOutputEnabled(
            $this->_moduleName
        ) || !$this->_isModuleDependenciesAvailable() || !$this->_isConfigDependenciesAvailable();
    }

This is only from my experience and there may be more reasons.