Fix bugs and add tests for sync storage

[barbogast]

No description provided.

[byteab]

Thank you @barbogast I will check that.
maybe I can pick the test part for now.

[byteab]

after finalizing the toThenable. would you mind to please help on resolving bugs by another PR.
currently tests are also failing for async as well.
if you have time would you please help me to spot why async test is failing.

[dai-shi]

Comparing against https://github.com/pmndrs/zustand/blob/master/tests/persist.test.tsx, this looks good to me.

[barbogast]

would you mind to please help on resolving bugs by another PR.

How about we merge this PR as it is? Then all the relevant code would be in pmndrs#403 and we would be back to one place in which the conversation happens. Working on toThenable should be easier then, because we've got green tests.

[byteab]

would you mind to please help on resolving bugs by another PR.

How about we merge this PR as it is? Then all the relevant code would be in pmndrs#403 and we would be back to one place in which the conversation happens. Working on toThenable should be easier then because we've got green tests.

Hmm, I was thinking to first have a final solution on how to implement toThenable(), and after that, we start bug fixing. because on the new version of toThenable() as provided on gist we handle try catch. and some commits on this PR may not be relevant to merge.
what do you think?

[byteab]

I will cherry-pick the test part for now.

[barbogast]

I guess the tests are the important part, so yeah, I agree. 7052e64 is also relevant, AFAICS, since it fixes the initial loading of the state from localStorage.

[byteab]

the tests are now available on async-await-fix branch.