Why does ORM `hasDataChanges()` behave incorrectly?

Question

I'm confused by the way Magento's ORM behaves when editing/saving an object; see the example below:

$model = Mage::getModel('vendor/model')
    ->setData(array(
        'name'        => 'Test,
        'description' => 'Info',
    ))
    ->save();

I now have a new record in the table, however this is where i'm confused.

$model = Mage::getModel('vendor/model')->load(1);
$model->setName('Test');  // THIS IS THE SAME
$model->setDescription('Info'); // THIS IS THE SAME

var_dump($model->hasDataChanges()); // returns true! (i expect false)
var_dump(($model->getData() !== $model->getOrigData())) // returns false (expected)

Surely the latter is how Magento should behave? Unless i'm missing something.

Answer 1

Looking into the setData function it appears that has data changes is always set to true even if technically the data has not changes.

This can be seen in Varien_Object function setData

public function setData($key, $value=null)
{
    $this->_hasDataChanges = true;
    if(is_array($key)) {
        $this->_data = $key;
        $this->_addFullNames();
    } else {
        $this->_data[$key] = $value;
        if (isset($this->_syncFieldsMap[$key])) {
            $fullFieldName = $this->_syncFieldsMap[$key];
            $this->_data[$fullFieldName] = $value;
        }
    }
    return $this;
}

Answer 2

Most of the times, I'm using the following code to check if a model changed:

$changed = $model->__toArray(array_keys($model->getOrigData())) != $model->getOrigData();

However, you'll need something else if you're going to check the product/category model after saving (for example from admin panel) or any other complex model. The problem there is that many values and types are different in $model->getData() vs $model->getOrigData().

Both product and category model have the updated_at field already updated. Product has also the stock_item object. Category has the image field in getOrigData() as type string and in getData() after save as array.