core-bundle/src/EventListener/AddToSearchIndexListener.php
public function onKernelTerminate(PostResponseEvent $event): void
    {
        if (!$this->framework->isInitialized()) {
            return;
        }

        $request = $event->getRequest();

        // Only index GET requests (see #1194)
        if (!$request->isMethod(Request::METHOD_GET)) {
            return;
        }

        // Do not index fragments
        if (preg_match('~(?:^|/)'.preg_quote($this->fragmentPath, '~').'/~', $request->getPathInfo())) {
            return;
        }

        /** @var Frontend $frontend */
        $frontend = $this->framework->getAdapter(Frontend::class);
        $frontend->indexPageIfApplicable($event->getResponse());
    }
public function onKernelTerminate(PostResponseEvent $event): void
    {
        if (!$this->framework->isInitialized()) {
            return;
        }

        $request = $event->getRequest();

        // Only index GET requests (see #1194)
        if (!$request->isMethod(Request::METHOD_GET)) {
            return;
        }

        // Do not index fragments
        if (preg_match('~(?:^|/)'.preg_quote($this->fragmentPath, '~').'/~', $request->getPathInfo())) {
            return;
        }

        /** @var Frontend $frontend */
        $frontend = $this->framework->getAdapter(Frontend::class);
        $frontend->indexPageIfApplicable($event->getResponse());
    }
Checks if the request can be indexed and forwards it accordingly.