Migration to single fetch crashes for end users

[jansedlon]

Hello,

I have tried to enable single fetch on version 2.13.1 and migrate a single route to single fetch. That means i removed defer function from loader.

Immediately after deployment i was getting Sentry errors. The first one seems to make sense because frontend keeps the cached version and for some time is sending data requests on the backend

However in the same trace it showed that it crashed because it couldn't load loader data.

Is this because i deployed the single fetch and loader migration in a single deployment? Is there a way to not crash it for the end users? 😅

[jansedlon]

Anyone?

[jarvis394]

Your useLoaderData probably returns an object which fields are promises that resolve to the actual data. I don't think you are able to access those fields before the promise resolves, hence the undefined in Sentry logs.

Does your TS typecheck bring any errors in app/routes/user+/stores+/details/route.tsx?

Refer to docs: https://remix.run/docs/en/main/guides/streaming#2-component-setup

[jansedlon]

It doesn't, because stores property is not a Promise. I think there's an issue with updating app to single fetch and migrating routes in a single deployment. Frontend is typically cached for end users because Remix fingerprints assets. When new deployment is release, backend returns data in a new format but frontend doesn't yet know that single fetch is enabled.

However i'm not sure if there's a way around that other than enabling single fetch in a separate deployment from migrating existing routes.