MSW fails to start on Safari

[ggascoigne]

When I run my app on Chrome and Firefox, everything works fine. If I run it on Safari it breaks, unless I exit Safari and restart it.

Digging a bit more, the code gets as far as

msw/src/utils/internal/requestIntegrityCheck.ts

Line 10 in c96ffa3

const { payload: actualChecksum } = await context.events.once(

and then that call to once() never returns.

If I reload Safari and it can read from cache, then msw initialization works as expected.

Any suggestions as to what I might be missing?

[ggascoigne]

I think that I've got it.

If you've followed one of the create-react-app templates that uses service-workers (e.g.
https://github.com/facebook/create-react-app/blob/3.x/packages/cra-template-typescript/template/src/index.tsx#L17
), then the call to serviceWorker.unregister() breaks msw registration on Safari. Remove this line and everything is back to working.