Avoid synchronous loading on client if options.ssr is false

[jdb8]

Summary

Fixes #345. See description there for more details.

tl;dr: in cases where ssr: false is set, this PR fixes the way we render the component on the client to match what the server is doing, avoiding problematic SSR hydration mismatches (https://reactjs.org/docs/react-dom.html#hydrate).

Test plan

Updated the SSR example to add a new letter, G, which is rendered on the page with both ssr: true and ssr: false. Without the change applied, the DOM looks like this (incorrect):

with the change applied, the DOM now correctly looks like this:

As mentioned in #345, I can't see any existing integration tests for SSR: if I missed some or if you think it's worth adding some, I'm happy to help set that up. Thanks in advance for reviewing!

[gregberge]

I think it makes sense, but we should add a test on it. There are actually some tests, could you just add one to cover this case?

[gregberge]

Hello @jdb8, any test?

[jdb8]

@gregberge sorry, this got lost somehow.

There are actually some tests, could you just add one to cover this case?

Would you mind pointing me to a good place to add this ssr integration test? The issue I had was that this is a change that you'd ideally want to validate across the server/component boundary, to verify that SSR hydration works fully. Apart from the examples folder (which I added to), I couldn't see anywhere suitable for such an end-to-end test without setting up a new suite.

[gregberge]

Thanks!