Magento 2 some functions' definition does not exist

Question

I use Magento 2.1.9, I came across these 2 that I could not find their definitions anywhere in the code:

Interface: \Magento\CatalogInventory\Api\Data\StockItemInterface

Class: \Magento\CatalogInventory\Model\Stock\Item

Method: setStockStatusChangedAutomaticallyFlag()

Interface: \Magento\Quote\Api\Data\CartInterface

Class: \Magento\Quote\Model\Quote

Method: getInventoryProcessed() and setInventoryProcessed()

Why magento hides these, or does not include documentation.

Thanks

Answer 1

PHP comes with so called "magic methods". All Magento models utilize them, and in your case - __call

As you can see in source: vendor/magento/framework/DataObject.php

public function __call($method, $args)
{
    switch (substr($method, 0, 3)) {
        case 'get':
            $key = $this->_underscore(substr($method, 3));
            $index = isset($args[0]) ? $args[0] : null;
            return $this->getData($key, $index);
        case 'set':
            $key = $this->_underscore(substr($method, 3));
            $value = isset($args[0]) ? $args[0] : null;
            return $this->setData($key, $value);
        case 'uns':
            $key = $this->_underscore(substr($method, 3));
            return $this->unsetData($key);
        case 'has':
            $key = $this->_underscore(substr($method, 3));
            return isset($this->_data[$key]);
    }
    throw new \Magento\Framework\Exception\LocalizedException(
        new \Magento\Framework\Phrase('Invalid method %1::%2', [get_class($this), $method])
    );
}

Any class that extends DataObject class has defined __call method for setters and getters, therefore methods mentioned by you are not explicitly defined in classes but utilize this logic.

Some of them (I do not know if most of them or just a few) are usually described in class docblock however some are not.

Personally I do not like all that "magic" because it leads to questions like your.