Fix race condition between simulator init and project loading#11196
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riknoll merged 2 commits intomicrosoft:masterfrom Mar 19, 2026
Merged
Fix race condition between simulator init and project loading#11196riknoll merged 2 commits intomicrosoft:masterfrom
riknoll merged 2 commits intomicrosoft:masterfrom
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Gate internalLoadHeaderAsync on componentDidMount completion so the simulator driver is guaranteed to exist before project loading accesses it. Add a defensive null guard in stopSimulator. Return the newProject() promise from the app init callback chain so errors propagate to the catch handler avoiding a blank screen if this step fails during init. Fixes microsoft/pxt-microbit#6081
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this stuff is always tricky, so we'll need to really hammer on this while testing, but LGTM
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Gate internalLoadHeaderAsync on componentDidMount completion so the simulator driver is guaranteed to exist before project loading accesses it. Add a defensive null guard in stopSimulator.
Return the newProject() promise from the app init callback chain so errors propagate to the catch handler avoiding a blank screen if this step fails during init.
Fixes microsoft/pxt-microbit#6081
Note: You can get a deterministic repro by adding e.g. await new Promise(resolve => setTimeout(resolve, 2_000)); to simulator's initAsync.