Proposal for safer `setState` about flutter HOT 3 OPEN

Thanks for the report @lukehutch
I am wondering if this use case / proposal is related to #128461 or #128384 ? or is it different ? If so, in which way ?

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It's not really related to either of them: both of those issues were about how to solve a complex scheduling issue I had when I was trying to create a new type of reactive widget. The latter of those issues was probably caused by calling SchedulerBinding.instance.addPostFrameCallback without first checking SchedulerBinding.instance.schedulerPhase (which is fixed in my new safeSetState).

This issue is much more general: I am trying to solve the red screen of death issue that I get when I accidentally call setState on a widget that is no longer mounted, after an await. I believe that that should never be an app-stopping error -- if a widget is no longer mounted, at a minimum setState should just silently fail.

The extra scheduler phase check is simply to allow setState to be scheduled to be run even during build (which would generally be a bad idea, because build should have no side effects). But the reason for doing this is so that safeSetState can be called from any function, with the widget tree in any state.

Basically I am proposing that setState should never throw an exception for any reason.

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Thanks for the update.

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