Magento dev tricks and tips

1/ To debug email sending code: 

 For example, when placing an order in FrontEnd; the order immediately gets marked as processed; and the quote is cleared. In order to debug sending email: 

 in file `vendor/magento/module-checkout/Controller/Onepage/Success.php`, disable this code: `$session->clearQuote();` 

 2/ Store object in memory per session 

 There is a deprecated technique still being used in Magento: use registry to store objects in memory. Example: 

 $this->registry->unregister('current_creditmemo'); $this->registry->register('current_creditmemo', $creditmemo);