"sys_page" is not set (is the defined string) in TypoScriptFrontendController and makes an error in the PageLinkBuilder

[dhuf]

We had the error in vendor/typo3/cms-frontend/Classes/Typolink/PageLinkBuilder.php line 303:

Call to a member function getMountPointInfo() on string

the $this->sys_page was not set.

To fix it we had to define it in the vendor/sitegeist/fluid-styleguide/Classes/Middleware/StyleguideRouter.php from line 96:

        // Build simple TSFE object for basic typolink support in styleguide
        $tsfe = GeneralUtility::makeInstance(
            TypoScriptFrontendController::class,
            $this->context,
            $GLOBALS['TYPO3_CURRENT_SITE'],
            $request->getAttribute('language', $site->getDefaultLanguage()),
            new PageArguments(0, '0', []),
            $this->frontendUserAuthentication
        );
        $tsfe->sys_page = GeneralUtility::makeInstance(PageRepository::class, $this->context);
        $GLOBALS['TSFE'] = $tsfe;

The fix was to init it:

$tsfe->sys_page = GeneralUtility::makeInstance(PageRepository::class, $this->context);

Maybe it might help somebody else.