[Bug]: flaky tests on HMR about storybook

[shilman]

cc @kasperpeulen

[kasperpeulen]

@vanessayuenn I think we should fix this as part of the module mock project.
I think that on HMR loaders are not rerun but the play function is.

@yannbf @JReinhold We should either:

• not rerun the play function on HMR
• or rerun both loaders and the play function on HMR

[JReinhold]

Agree. If we want to be consistent with test runners like Vitest, I think we should rerun the whole pipeline on HMR.

[yannbf]

I agree as well. @kasperpeulen can you add this to the project?

Before we even do anything, @tmeasday @shilman do you know why loaders are not rerun on HMR? Is there some important information we're missing somehow?

[tmeasday]

Hey folks, happy to chat about this. @ghengeveld & I thought carefully about what should and shouldn't rerun on HMR when we first created play functions. You can see the intended behaviour in the tests:

On HMR:

• Loaders rerun
• Play functions run

On args/globals change:

• Reruns loaders if the story hasn't finished rendering

• Reruns the renderToCanvas function

• Re-renders (and reruns the play function) if the play function was still running

It looks like we don't have explicit tests for what happens with loaders or the play function (if it has completed) when you change args/globals (my bad, we should fix this) but I believe:

• loaders rerun
• play functions do not.

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TLDR

@kasperpeulen

I think that on HMR loaders are not rerun but the play function is.

The tests say this is incorrect. I guess they could be wrong 🤷