Updates to observables in `firstUpdated` not working about lit-mobx HOT 9 CLOSED

Amazing! Thanks so much, might be the fastest fix I've ever seen!

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Interesting, please let me know how your investigations pan out and I'll try and take a deeper look at this asap.

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Have produced a quick repro:

https://stackblitz.com/edit/typescript-zpfftr

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Ok what appears to be happening is that the observable tracking from the Reaction setup is not completed until after firstUpdated is called, this is due to firstUpdated being called synchronously after the render completes.

The Reaction we setup is observing the access through the performUpdate function which in turn triggers render, but the reaction captures the state after this function completes. So making a change in firstUpdated is not detected because its already set to the new value as far as the Reaction is concerned..

Not exactly sure the best approach here to fix. @justinfagnani any suggestions? I feel like we 'could' requestUpdate after track to force a second render pass to capture any changes after firstUpdate but this seems less than ideal in the majority of cases where state is not modified in firstUpdate. However we're clearly violating the description of firstUpdated right now so we do need to fix this one somehow I think?

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One approach that appears to work is to create the Reaction over the update method rather than performUpdate, this way the reaction is setup over the state before firstUpdated is called and we get a requestUpdate reaction after firstUpdated completes. @justinfagnani do you see any issues with this?

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I suspect this will also be a problem for state changes in updated(), and in update() after the super.update() call.

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I guess we could setup separate reactions around each of these functions in a similar manner? Its a little more code, but not a lot, and I guess would solve in each case.

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Tracking super.update() might be ok. Then any subclasses that make state changes after their own super.update() call should work.

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@cannoneyed this fix has been published under 0.0.4.

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