Where does Magento 2 URL Segment Parsing Happen

Question

In Magento 2 routing, the system parses the URL segments into three sections

module-or-front/segment2/segment3

Which specific class file does this happen in?

Put another way, the request object has a getModuleName method that looks like this

public function getModuleName()
{
    return $this->module;
}

Where does Magento 2 get the string that ultimately sets the module property?

Answer 1

I think everything is set up in Magento\Framework\App\Router\Base::matchAction
The line you are looking for is $request->setModuleName($moduleFrontName); but I guess you wanted the full method.
This matchAction method is called by the match method from the same class that is called by Magento\Framework\App\FrontController::dispatch() ....and so on.

[EDIT]
not 100% sure, but I think the actuall splitting of the url is done in Zend\Uri\Uri::makeRelative()

$pathParts = preg_split('|(/)|', $this->getPath(), null, PREG_SPLIT_DELIM_CAPTURE | PREG_SPLIT_NO_EMPTY);