TYPO3 Core

You can also have a look at the latest version of this patch, which already uses the invoker: https://review.typo3.org/c/Packages/TYPO3.CMS/+/83718

Heyho @Garvin Hicking Using the invoker prevents the array key warnings.

Here are both ways configured that they do not need the patch:

The invoker way:

            $content = $view->getRenderingContext()->getViewHelperInvoker()->invoke(
                CObjectViewHelper::class,
                [
                    'typoscriptObjectPath' => $blockType,
                    'data' => $data->getRawRecord()->toArray(),
                    'context' => $context,
                    'table' => 'tt_content',
                ],
                $subView->getRenderingContext(),
            );

The resolver way:

            $cObjectViewHelper = $view->getRenderingContext()->getViewHelperResolver()->createViewHelperInstance('f', 'cObject');
            $cObjectViewHelper->setArguments([
                'typoscriptObjectPath' => $blockType,
                'data' => $data->getRawRecord()->toArray(),
                'table' => 'tt_content',
                'currentValueKey' => null, // prevent array key warning
                'context' => $context,
            ]);
            $cObjectViewHelper->setRenderingContext($subView->getRenderingContext());
            $content = $cObjectViewHelper->render();

Bottom line: You think there is no need to add the null coalescing operator to the optional arguments? (see patch)

Personally, yes, I'd follow Simons lead here and would say that the Invoker way is the suggested way to approach it, allowing the Core for future flexibility. While adding array checks in there would help your case, I think it would make the code a bit more "heavy" and extra weight (albeit only little).

So if you're fine with it I would prefer to close the issue, yes. Thanks so much for adding in the resulting code that you worked out, and for offering the patch in first place! :)