Classes/Console/Service/XsdGenerator.php
protected function getClassNamesInNamespace($namespace)
    {
        $packageKey = $this->getPackageKeyFromNamespace($namespace);
        $viewHelperClassFilePaths[] = $this->packageManager->getPackage($packageKey)->getPackagePath() . 'Classes/ViewHelpers/';
        if ($packageKey === 'fluid') {
            $viewHelperClassFilePaths[] = realpath(PATH_site . 'typo3/') . '/../vendor/typo3fluid/fluid/src/ViewHelpers/';
        }

        return $this->getClassNamesInPaths($viewHelperClassFilePaths);
    }
protected function getClassNamesInNamespace($namespace)
    {
        $packageKey = $this->getPackageKeyFromNamespace($namespace);
        $viewHelperClassFilePaths[] = $this->packageManager->getPackage($packageKey)->getPackagePath() . 'Classes/ViewHelpers/';
        if ($packageKey === 'fluid') {
            $viewHelperClassFilePaths[] = realpath(PATH_site . 'typo3/') . '/../vendor/typo3fluid/fluid/src/ViewHelpers/';
        }

        return $this->getClassNamesInPaths($viewHelperClassFilePaths);
    }
Get all class names inside this namespace and return them as array.
This has to be done by iterating over class files for TYPO3
as the Extbase Reflection Service cannot return all implementations
of Fluid AbstractViewHelpers

@param string $namespace
@return array Array of all class names inside a given namespace.