dillon1000/react

Client render Suspense content if there's no boundary match (#16945)

Without the enableSuspenseServerRenderer flag there will never be a boundary match. Also when it is enabled, there might not be a boundary match if something was conditionally rendered by mistake.

With this PR it will now client render the content of a Suspense boundary in that case and issue a DEV only hydration warning. This is the only sound semantics for this case.

Unfortunately, landing this will once again break #16938. It will be less bad though because at least it'll just work by client rendering the content instead of hydrating and issue a DEV only warning.

However, we must land this before enabling the enableSuspenseServerRenderer flag since it does this anyway.

I did notice that we special case fallback={undefined} due to our unfortunate semantics for that. So technically a workaround that works is actually setting the fallback to undefined on the server and during hydration. Then flip it on only after hydration. That could be a workaround if you want to be able to have a Suspense boundary work only after hydration for some reason.

It's kind of unfortunate but at least those semantics are internally consistent. So I added a test for that.